Recent Developments in the Technical Examination of Early Netherlandish Painting (Museums at the Crossroads) 9782503509938, 1891771353, 2503509932

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METHODOLOGY, LIMITATIONS & PERSPECTIVES BREPOLS

9782503509938

Recent Developments in the Technical Examination of Early Netherlandish Painting: Methodology, Limitations & Perspectives

RECENT DEVELOPMENTS IN THE TECHNICAL EXAMINATION OF EARLY NETHERLANDISH PAINTING: METHODOLOGY, LIMITATIONS & PERSPECTIVES Edited by Molly Faries and Ron Spronk

Harvard University Art Museums, Cambridge In collaboration with Brepols Publishers, Tumhout, Belgium

Library of Congress Cataloging-in-Publication Data Recent developments in the technical examination of early Netherlandish painting : methodology, limitations & perspectives / edited by Molly Faries and Ron Spronk. p. cm. Proceedings of a 1996 symposium organized by the Harvard University Art Museums. “D /2003/0095/137”—Copyright p. ISBN 1-891771-35-3 (Paper : alk. paper)-ISBN 2-503-50993-2 (Brepols) 1. Painting, Netherlandish—Expertising—Congresses. 2. Painting—Research—Methodology—Congresses. I. Faries, Molly. II. Spronk, Ron. ND635.R33 2003 759.9492'09'031—dc21 2003014518

Published in the United States of America by the Harvard University Art Museums, Cambridge, Massachusetts. Published in Belgium and distributed by Brepols Publishers, Turnhout, Belgium.

The symposium and this publication were made possible by the support of the M. Victor Leventritt Lecture Fund and the Andrew W. Mellon Foundation.

Copyediting: Carolann Barrett and Marsha Pomerantz.

Cover illustration: Workshop of Dirk Bouts, Virgin and Child, c. 1460. Oil (and tempera?) on wood panel, 30.5 x 21.6 cm. Fogg Art Museum, Harvard University, Cambridge, Massachusetts, 1959.186. Gift of Mrs. Jesse Isidor Straus in memory of her hus­ band, Jesse Isidor Straus, class of 1893. Center and left: Digital IR R composite and X-radiograph of the same painting.

D/2003/0095/137 © 2003, Brepols Publishers n.v.,Turnhout, Belgium / President and Fellows of Harvard College All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise without the prior permission of the publishers, except by a reviewer, who may quote brief passages in a review. Printed in the E.U. on acid-free paper

C ontents

Director’s Foreword

Preface

VII

IX

Molly Faries Technical Studies of Early Netherlandish Painting: A Critical Overview of Recent Developments

1

R on Spronk Standing on the Shoulders of Giants:The Early Years of Conservation and Technical Examination of Netherlandish Paintings at the Fogg Art Museum

39

J. R . J. van Asperen de Boer Slowly Towards Improved Infrared Reflectography Equipment

57

Peter Klein Dendrochronological Analyses of Netherlandish Paintings

65

Teri Hensick The Fogg’s Copy after a Lost Van Eyck: Conservation History, Recent Treatment, and Technical Examination of the Woman at Fier Toilet

83

Gianfranco Pocobene and R on Spronk The Fogg Art Museum’s Virgin and Child from the Workshop of Dirk Bouts: Findings from Technical Examinations and Recent Conservation Treatment

97

E. Melanie Gifford, Susana Halpine, Suzanne Quillen Lomax, and Michael R. Schilling Interpreting Analyses of the Painting Medium: A Case Study of a Pre-Eyckian Altarpiece Flenry Lie Digital Imagingfor the Study of Paintings: Experiences at the Straus Center for Conservation

107

117

Maryan Wynn Ainsworth What’s in a Name? The Question ofAttribution in Early Netherlandish Painting Glossary

135

149

Bibliography

171

Color Plates

193

Illustration Credits

213

V

D irecto r’s Foreword Edward Forbes, the director of the Fogg Art Museum from 1909 until 1944, titled an article that he wrote in 1920, “The Technical Study and Physical Care o f Paintings.” The insertion of two words, “N orthern Panel,” would neatly adjust his pioneering concept to the focus o f this present volume. Yet publication— that is, the wider dissemination of observed facts and research results from the physical study of artworks— was only one aspect of Forbes’s project, one that would lead to the Fogg Museum’s seminal pubhcation in 1932 of volume 1, number 1 of Technical Studies in the Field of the Fine Arts. Its very first article, by Harold J. Plenderlieth: “Notes on Tech­ niques in the Examination of Panel Paintings.” In his larger project, Forbes collected artist’s manuals and specimens of historical and contem­ porary artist’s materials, along with paintings themselves (often panel paintings in decrepit yet revealing condition). Paintings, books, and artist’s materials served collectively as a reference library for technical study at the Fogg Art Museum. Forbes designed a properly lit and equipped paint­ ing “laboratory,” as it was then called, for the new Fogg building, opened in 1927. As its staff, he hired specialists in scientific analysis and painting conservation, to formulate experiments and test procedures. In the “laboratory,” he himself taught graduate students by example and practice how and with what paintings were made. In every facet of this enterprise, Forbes emphasized to his own and the following generations of “museum m en” (which included women) the irreplaceable value o f knowledge about the physical attributes of works of art. A career could lead to the scholarly investigation of those attri­ butes, and to the prizing out of facts about the composition and m ethod o f the artwork and about its initial presentation and subsequent use, or it could lead to the preservation of artworks through ethical conservation procedures and documentation.Yet the ideal, Forbes realized, would not he in the individual career. Rather, the ideal would be for art historians, scientists, and con­ servators to comprise a team, equipped with reference samples and instrumental technology. Edward Forbes’s Fogg Art Museum was the locus classicus of such a team, and we who follow him are determined that it remain so today and in the future. To that end, over the past two decades, the Harvard University Art Museums have sought and received generous funding from the Andrew W. Mellon Foundation. Various grants have sup­ ported graduate and postgraduate internships for conservators in training and conservation sci­ entists, analytical equipment purchases, and a major conference on the digital imaging of artworks. We have also received a Mellon endowment for internships to be awarded to Harvard students to undertake projects based within the Museums’ collections. Many of our Mellon interns have worked in what is now known as the Straus Center for Conservation and Technical Studies, which inhabits the same spaces as Forbes’s original “laboratory.” More specifically, support from the Mellon Foundation enables the publication of this com­ pilation of papers on the technical study of early Netherlandish panel painting. The authors of this volume have variously described the history, present state, and prospects of various research approaches; documented a sample case of technical study and treatment; and characterized the uses of specific instruments for examination and documentation. Above all, they have critically examined the nature and value of methods for technical analysis within this specialty so that art historians, whether curators or academics, and conservators alike will fully understand the poten­ tial— presciently formulated by Edward Forbes eighty and more years ago— for learning from physical works of art.

VII

We are grateful for support for the symposium from the M. Victor Leventritt Lecture Fund, established through the generosity of the wife, children, and friends of the late M. Victor Leven­ tritt, Harvard class of 1935. O ur thanks are also due to the editors of this volume, R o n Spronk, associate curator for research at the Straus Center for Conservation, and Molly Faries, professor of history of art at the Rijksuniversiteit Groningen and Indiana University Bloomington, and to our authors, who have revisited their symposium papers given several years ago to prepare them for publication in the twenty-first century. Collectively, they offer to a wider public great advances on that first article in the first issue of Technical Studies in the Field of the Fine Arts. I am confident that the usefulness o f these presentations has only begun, as inspiration and guide for further research. Marjorie B. Cohn Acting Director, Harvard University Art Museums Carl A. Weyerhaeuser Curator of Prints

VIII

Preface O n November 2,1996, the Harvard University Art Museums organized the symposium “Recent Developments in the Technical Examination of Early Netherlandish Painting: Methodology, Lim­ itations, and Perspectives.” The symposium occurred in conjunction with the opening of the renovated and enlarged Straus Center for Conservation and Technical Studies, the reopening of Warburg Hall as an exhibition gallery, and the opening o f the exhibition Investigating the Renais­ sance at the Fogg Art Museum.The symposium was generously sponsored by the M.Victor Leventritt Lecture Fund, established through the generosity of the wife, children, and friends of the late M.Victor Leventritt, Harvard class of 1935. The publication of these papers has been fund­ ed by the Andrew W. Mellon Foundation, to whom we are equally grateful. The technical study o f early Netherlandish painting has been, and continues to be, both a fast-moving and complex field. Given the rapid changes in research methods and investigative equipment and techniques, a pressing need had arisen for an integrated and evaluative overview of these developments. The Harvard symposium brought together leading experts from all fields of technical investigation for groundbreaking sessions on topics ranging from the long-neglected history of technical studies to the latest imaging technology. We would like to express our deep gratitude to James Cuno, former director of the Harvard University Art Museums, for his strong support for technical studies o f works o f art, and to H enry Lie, director o f the Straus Center, for his innovative leadership in this field. We are indebted to the speakers at the symposium whose papers are published here, and to Ivan Gaskell, the late John Shearman, and Seymour Slive, who discussed the presentations during the meeting. The papers o f Lome Campbell and Richard Newman, on Jan van Eyck’s Portrait of Giovanni (?) Arnolfini and His Wife and Rogier van der Weyden’s St. Luke Drawing the Virgin, respectively, were published elsewhere,1 but we are fortunate to include here Melanie Gifford, Susana Halpine, Suzanne Quillen Lomax, and Michael Schilling’s research, not presented at the symposium, on the pre-Eyckian Antwerp—Baltimore quadriptych. We would like to also thank our colleagues who helped us compile the illustrated glossary of technical terms, especially Narayan Khandekar, Kate Olivier, and Richard Mulholland. In addi­ tion, we thank Nancy Hurley, who provided essential support for the organization of the sym­ posium, and Carolami Barrett and Marsha Pomerantz, who carefully copyedited this book. The editors and authors hope that this volume o f the Harvard symposium papers— revised, updated, and accompanied by a comprehensive overview o f the topic and a glossary— will pro­ vide a valuable reference on technical studies o f early Netherlandish painting and make research in this vital field of investigation more accessible to scholars, conservation professionals, scien­ tists, and students. Molly Faries R on Spronk

1. See Campbell 1998 and Newman 1997.

IX

Technical Studies o f Early N etherlandish Painting: A C ritical O verview o f R ecen t D evelop m en ts M olly Faries Rijksuniversiteit Groningen and Indiana University Bloomington

Introduction

There are clear signs that technical study of early northern European painting has reached a new stage of self-definition. The long associ­ ation of technical examination with early Netherlandish painting has been a productive one, leading, by the end of the twentieth cen­ tury, to a critical surge in activity. Ever since the pioneering 1950s research by Paul Coremans at Brussels’s Centre National de Recherches “Primitifs Flamands” (as it was called then), technical studies and early Netherlandish paint­ ing have been inextricably linked. The ambi­ tious plans of the Brussels Center to catalogue all early Netherlandish paintings included tech­ nical examination on a routine basis through X -R A D IO G R A PH Y * and various types o f spe­ cialized photography, such as INFRARED (i r ) p h o t o g r a p h y . This set the general parameters o f the field at the time, but by the 1970s and 1980s, newer methods were being introduced that expanded the potential of the EXAMINA­ T IO N

r o u t in e . In f r a r e d r e f l e c t o g r a p h y

and DEND RO CHRON O LO GY emerged as extremely productive investigative tools. The findings of these methods, and the issues they generated, stimulated so much discussion that one can speak of a reshaping of the entire dis­ cipline. One obvious indicator of this new sit­ uation is the number o f surveys o f the field that have appeared injust the last few years. In 1995, Jellie Dijkstra published an article on technical investigation as an approach charac­ terizing the m odern study o f early N ether­ landish painting.The Harvard symposium that forms the basis for the present volume was held in 1996.The 1997 issue of the London Nation­ al Gallery Technical Bulletin was devoted in its entirety to the materials and techniques of ear­ (i r r )

* Terms in

SMALL CAPS

ly northern European painting. In 1998, a sym­ posium was held at the Metropolitan Muse­ um of Art in New York in conjunction with the m useum ’s exhibition From Van Eyck to Bruegel. The talks highlighted im portant research trends related to early Netherlandish painting, one of which was technical investi­ gation. More recently, new names have been proposed for this type o f research. Some have suggested that “technical study” should be ele­ vated to its more proper place as “technical art history.” Others want to define themselves as “researchers of painting technology sources.” W hether or not these labels receive general acceptance, the desire for a more authoritative title implies that there is a new sense o f pur­ pose felt by those working in the field of tech­ nical studies. The recent surveys of the field all take slight­ ly different approaches. Jellie Dijkstra’s article was the only study already published by the time of the Harvard symposium in 1996.1 It appeared in Dutch in a volume o f historiographic and methodological essays on the study o f early Netherlandish painting and should soon be available in English. It provides an excellent introduction to the usual methods of technical investigation: dendrochronology, infrared pho­ tography, infrared reflectography, X-radiography, and the microscopic study of paint surface and CROSS SECTIONS. The article also demon­ strates possible applications, such as the recon­ struction of dismembered altarpieces, in this case a triptych by the Master of the Legend of Saint Catherine. Dijkstra s carefully selected examples of technical investigation are organized accord­ ing to the layered structure o f the paintings, from SUPPORT, to G RO U ND , to UNDERDRAW ­ ING, to PAINT LAYERS, and are derived for the

can b e found in the glossary.

A CRITICAL OVERVIEW OF RECENT DEVELOPMENTS

1

most part from the circles of the Master of Flémalle and Rogier van der Weyden. The London National Gallery Technical Bul­ letin that appeared a year after the Harvard sym­ posium is based on new research data compiled by specialists on the museum’s staff—Rachel Bilhnge, Lome Campbell,Jill Dunkerton, Susan Foisterjo Kirby,Jennie Pile, Ashok Roy, Mari­ ka Spring, and Raymond W hite.2 The issue is commendable for its combination of the study of early Netherlandish painting with German and French examples. Because it includes northern German works, the Bulletin provides one of the best overviews to date o f GILDING in early northern painting. It also incorporates what is undoubtedly the most thorough sur­ vey of the known documentary sources since M errifield and other nineteenth-century authors. Based on the examination o f around two hundred paintings, this issue of the Bulletin provides a solid factual grounding in the mate­ rials of early northern European painting. Filled with technical details and followed by a table with the results from medium analysis, the text serves as a basic reference for the field. As such, it provides valuable comparanda for the tech­ nical data published in recent catalogues of ear­ ly Netherlandish painting, such as those of Brussels, Frankfurt, Kansas City, London, R o t­ terdam, and Washington, as well as the Fogg Art Museums study of its Netherlandish collection. In 1998, my lecture at the M etropolitan symposium, which has now been published, presented another overview o f the field.3The first part of the lecture focused on five high­ ly im portant Netherlandish paintings, all in U.S. collections, as examples whose attribu­ tion and character have been clarified by recent technical study. A second part o f the lecture, entitled “Beyond Attribution,” brought out key issues that have emerged in the liter­ ature o f the field, such as the function of underdrawings, CO PYIN G RO U TIN ES and the use of models, and the painting technologies of the workshop. Finally, the Rembrandt scholar Ernst van de Wetering has lectured several times in the last few years about the place o f technical investi­ gation in Dutch art historical research.4 While not specifically directed to the study o f early ?

Netherlandish painting, van deWetering’s com­ ments have added important points about his­ toriography and the main lines of questioning found in technical studies. My introduction to this volume is organized differently than the essays discussed above. As commentary accompanying the Harvard sym­ posium papers, it traces the development of research methods utilized in the study of ear­ ly Netherlandish painting, rather than follow­ ing the stages o f the painting process or the sequence of the examination routine. Harvard was fortunate in hosting researchers such as J. R. J. van Asperen de Boer and Peter Klein, who developed these methods and have carried out extensive studies themselves. All of the authors in this volume, however, speak from firsthand engagement with the material. E. Melanie Gif­ ford provides a critique of some o f the latest methods employed in pigment and medium analysis. The essays by Teri Hensick and by Gianfranco Pocobene and R on Spronk include up-to-date reasoning about conservation issues. Henry Lie presents his pioneering applications o f the computer to the handling of tradition­ al technical documents such as INFRA RED images and X-rays. Maryan Ainsworth address­ es current thinking about the complicated issue of attribution in early Netherlandish painting. Since these essays represent the very latest eval­ uations o f the approaches and techniques that characterize the investigation of Netherlandish painting, they are state-of-the-field contribu­ tions. My own essay places more emphasis on the ideas that accompany the methods. But because I speak as another practitioner, my intention is to help bridge the gap between the examination of a painting and the interpreta­ tion of the results. I begin below with a reference to historiog­ raphy. Since the historiography of technical stud­ ies has been almost nonexistent until the last few years, R on Spronk’s essay helps put the field on a more solid footing; it is another indicator of the greater visibility the field has today. Spronk’s paper elucidates the important role Harvard Uni­ versity has played in the development of tech­ nical studies. Following the historiography, I comment on the traditional technique of Xradiography and then turn my attention to recent trends in technical studies, beginning with mate­

A CRITICAL OVERVIEW OF RECENT DEVELOPMENTS

rials analysis of the paint stage of Netherlandish works. In this section, I also discuss the infor­ mation infrared reflectography can provide about PIGMENTS, modeling techniques, and PAINTLAYER STRUCTURE. The possibility of integrat­ ing information from different methods of study, first suggested in the section on PAINT, is devel­ oped further in the discussion of the coordina­ tion of technical documents. The main part of the essay concentrates on the two methods that, in the last twenty to thirty years, have made by far the greatest contributions of visual material and research data to the technical study of Netherlandish painting: dendrochronology and infrared reflectography.

T h e First A ca d em ic H o m e o f T echnical Studies: Harvard U niversity

The term “technical studies,” taken from the name of the Fogg Museum’s department and its journal, Technical Studies in the Field of the Fine Arts, has been used to describe research in this field for more than nine decades. Still, the full extent of technical studies’indebtedness to the Fogg has never been written about in any detail, and R on Spronk’s essay on the early years at the Fogg therefore does a great service. There is almost no historiography of technical studies, and only one literary tradition that can be con­ sidered historiographic background: that asso­ ciated with Jan van Eyck’s legendary invention of the oil-painting technique. It is significant, then, that the Fogg’s “founding fathers” also became involved with what they called the “Van Eyck Problem.” (For the current state of the field on this point, see below and the paper by Melanie Gifford.) But their more encompass­ ing contribution was surely the advancement o f the conservation profession, which was always in concert with technical research.The words of the Fogg’s director, Edward Forbes, in 1920 do indeed seem prophetic: “I hope that some day a technical school may be established, perhaps at Harvard, where painters, restorers, and museum officials may learn about the chemistry o f paintings and the care of them, on truly scientific principles.”'’ In keeping with this ambition, the Fogg was the first U.S. muse­ um to have a chemist on its staff. Many o f the investigative approaches taken in the early years at the Fogg are still o f vital interest today, such

as making copies and reconstructions, devising test panels, and studying the aging process. Other recent publications highlight the Fogg’s important place in technical studies and con­ servation history.6At a Getty symposium on the structural conservation of panel supports James S. Horns traced the Fogg’s contributions to the development of new methods o f backing pan­ els.7 Norman Muller, in a recent article on con­ servation history at Princeton University, stresses the importance during the World War II years o f those individuals who had been trained in the Harvard M ethod.8 Francesca Bewer is now preparing a broader overview of the history of both conservation and technical examination at the Fogg.9And in their historiographic notes on the study of Netherlandish painting, Roger Van Schoute and Brigitte de Patoul cite tech­ nical studies at the Fogg as the immediate prece­ dent for work at the Brussels Center.10 In fact, it was the chemist Rutherford John Gettens whose research linked directly to sub­ sequent technical studies of early Netherlandish painting. In 1947 Gettens was one of the con­ servation scientists who confirmed the redis­ covery of lead-tin yellow, a pigment that has had its own particular history in Netherlandish studies.The next year, while on a Belgian-American fellowship, Gettens studied Dirk Bouts’s Holy Sacrament Altarpiece and began his collabora­ tion with Paul Coremans and Jean Thissen. These scholars went on to write an article on the technique of the “Flemish primitives” for the first volume of Studies in Conservation.^1The article develops a scientifically based descrip­ tion of pigments, paint-layer structure, and MEDI­ UM; it cannot be regarded as anything other than a foundation document for the field. Gettens was aware of the need to recover the early history o f technical studies. In 1974, he spoke to conservators at the American Institute for Conservation meeting in Cooperstown, New York. “To come to the point quickly,” he said, “I think we should begin to think about collecting material for a history of the conser­ vation of cultural property.” He went on to say, “Knowledge of the beginnings and growth of our profession is a necessary background for training programs in art conservation” and “we wouldn’t really be a profession without a step­

,4 CRITICAL OVERVIEW OF RECENT DEVELOPMENTS

3

wise story of growth.”12 Afterward he went to his summer home and began making hand­ written notes on the early days at the Fogg. But his sudden death, unfortunately, cut short these recollections of the late 1920s and early 1930s. O ther articles on the Fogg’s early researchers have since appeared, and the importance of the Harvard Method has been generally acknowl­ edged. It is therefore entirely appropriate for this volume to include Spronk’s essay, as one that takes up Gettens’s unfinished work.

X -R ad iograp h y

As Spronk relates, it was Alan Burroughs’s work with X-radiography from the late 1920s to 1947 that resulted in one of the first exten­ sive archives o f technical documents. As indi­ cated by the Fogg’s plans to scan and archive this material, Burroughs’s X-rays have retained their usefulness. The same is true of the book Bur­ roughs wrote in 1938 about X-ray, which, along with the one published the same year by Chris­ tian Wolters, remains a basic text in this field.13 Neither Burroughs nor Wolters has ever been ful­ ly replaced. By the time the Brussels Center began its systematic study of Netherlandish paintings, X-radiography was employed as a standard inves­ tigative technique. In the 1960s in particular, the Center routinely published an X-ray of each painting studied.14 Since then, X-rays have been published on a fairly regular basis, and many museums have been able to obtain X-radiographs for their files on individual works. As a result, most art historians, as well as the gener­ al public, are relatively familiar today with the possibilities of this technique. Since Burroughs, X-radiography has hardly ever been used as a single investigative technique. However, in 1967, the Centraal Museum in Utrecht published a catalogue on the systematic study by X-ray of key works in their collection.The catalogue pro­ vides textbook examples of various X-ray find­ ings.13 Other instructive examples of X-rays can be found in a more recent article by Roger Van Schoute and Hélène Verougstraete. Published in 1986, it is the best current overview of X-ray techniques and their application in art history, especially regarding earlier European painting.16 Recent years have seen changes in the use of X-ray, and it is likely that there are more changes 4

on the horizon. Infrared reflectography (IRR) has revitalized interest in X-ray. IR R and X ray are complementary techniques, since they both penetrate into a painting’s layered structure to reveal the interrelationship of the layout draw­ ing and the subsequent application(s) of paint. By using X-ray in combination with IR R , COM­ POSITIONAL CHANGE can be studied quite pre­ cisely (see that term and DELIMITATION in the glossary). Paul Coremans included many X-rays in his initial study of the Ghent Altarpiece, and van Asperen de Boer’s restudy of this material provides us with several excellent examples of the careful reading of infrared reflectography in combination with X-ray. It was possible to clar­ ify that the eyes of the Deity first looked down­ ward in the UNDERPAINTING and were changed with black paint into a more open-eyed, abstract­ ed gaze in a later paint stage.17 O ther studies combining IR R and X-ray are mentioned below in the section on infrared reflectography, espe­ cially regarding copying routines, as well as the creative underpainting stage in Rogier van der Weyden’s works.The ample evidence for major alterations in the composition of Rogier’s Saint Luke Drawing a Portrait of the Virgin in the Muse­ um of Fine Arts, Boston, published by Rhona Macbeth and R on Spronk in 1997, was revealed primarily by X-radiography, in combination with cross sections and IR R .18 Dendrochronology has also been used in combination with X-radi­ ography, since it has sometimes been possible to measure the annual GROWTH RINGS of a panel on X-ray film. X-rays can now be scanned and combined with other images of a painting using computer LAYERING techniques. For the Dirk Bouts Virgin and Child discussed in this volume, Spronk merged the X-ray of the painting with a 20-percent image in VISIBLE LIGHT, which is helpful in visualizing the underpainting stage of theVirgin’s blue robe.19A significant advance in the study o f paintings and other art objects will occur with the development of portable Xray units that can obtain “live” images. Then it will be possible to use X-radiography as a scan­ ning technique, as can now be done with infrared reflectography.

M aterials A nalysis o f the Paint Stage

The symposium on Robert Campin in Lon­ don in 1993 can be said to have marked a

A CRITICAL OVERVIEW OF RECENT DEVELOPMENTS

renewal in the serious study of early Nether­ landish painting technique. As one scholar not­ ed, before the symposium there was no information at all on the pigments or paintlayer structure o f Campin’s works.20 The sym­ posium rectified this situation, and London researchers later assembled related information in case studies of five paintings associated with Campin s pupil and studio assistant, Rogier van der W eyden.21 1993 is also the year Pirn Brinkmans study on Jan van Eyck’s oil-painting technique appeared.22 The book is primarily a historiography of the early literature on the legend of Van Eyck’s discovery, as well as a his­ torical review o f the various scientific approaches taken to the analysis o f the OIL M ED IU M . The text also includes a summary o f analytical work done by researchers at the Brussels Center, since PAINT SAMPLES taken from the Ghent Altarpiece in the 1950s— as well as new samples— had been reinvestigated with newer analytical techniques.23 Pigment and medium studies rely, of course, on the taking of samples. Since sampling usu­ ally has to be carried out as part of a special ini­ tiative, such as a conservation treatment, this material is understandably limited, and overall coverage is not always possible. Pigment and medium studies have also been limited by the justifiably ethical stance of researchers that sam­ pling should be undertaken only when all other methods of investigation have been exhausted. Still, complicated issues related to the substances of paint, medium, and intermediate layers often require analysis at the molecular level. Now that more sophisticated, nondestructive instrumen­ tal methods have become the norm in this field of study, it is all the more important to encour­ age what can be seen as a new phase in the investigation of painting technique.The micro­ chemistry and STAINING TECHNIQUES that have been used in the past have largely given way to newer laboratory methods that do not alter or destroy the sample in the process of studying it. Once the cross section exists, it can be submit­ ted for study using methods of this type, such as SCANNING ELECTRO N M ICROSCOPY (SEM) with energy-dispersive X-ray analysis (EDX) or energy-dispersive spectroscopy (EDS), which employ the X-ray analysis capabilities of the scanning electron microscope to identify inor­ ganic materials without damaging the sample.

Much existing, unpublished material, languish­ ing in museum files or research archives, can be studied anew. The articles byTeri Hensick and by Gianfranco Pocobene and R on Spronk use these instrumental methods, and Melanie Gif­ ford mentions a new refinement in the com­ bined techniques o f GAS CHROM ATOGRAPHY MASS SPECTROSCOPY (g c - m s ) used for medium analysis. At the moment, other promising meth­ ods of cross-section and medium analysis, such as IMAGING SIMS, are in development.24 Melanie Gifford’s paper in this volume is one of several recent critical studies that apply these techniques to Netherlandish painting and is therefore an essential contribution. The range of pigments in early Netherlandish painting is not large (nor did the available range change radically until the introduction of syn­ thetic pigments in the nineteenth century). As is well known, many pigments were derived from natural sources, such as earths for red and yellow ochres, minerals for azurite, natural ultramarine, and malachite, and DYESTUFFS for indi­ go and red and yellow LAKES. Other colors, such as lead white, lead-tin yellow, vermilion, verdi­ gris, and smalt, were manufactured. Covering around two hundred paintings, the 1997 Lon­ don study is the broadest survey verifying the presence of these pigments in early Netherland­ ish painting.25 Other scholars have confirmed these findings. In a 1991 paper, J. R . J. van Asperen de Boer had already developed a sim­ ilar list of pigments occurring in early northern European painting, based on published exam­ ples.26 His research has also defined the pigment range for sixteenth-century northern Nether­ landish painting as including most o f the pig­ ments mentioned above, along with blue verditer (an artificial azurite), globular green verditer (an artificial malachite), a green copper sulfate, orpi­ ment, and realgar (although the latter two pig­ ments may have been imported from Italy).27 Pigments used by individual artists such as Jan van Eyck, Rogier van der Weyden, Albrecht Dürer, Lucas van Leyden, and Jan van Scorel have been published,28 and individual occur­ rences in the works o f other painters can also be found by consulting the important refer­ ence work Artists’Pigments:A Handbook of Their History and Characteristics.29The best basic intro­ duction to these pigments in English comes

A CRITICAL OVERVIEW OF RECENT DEVELOPMENTS

5

from a field other than Netherlandish painting. London’s Art in the Making catalogue for Ital­ ian painting before 1400 reviews the pigments, most of which remain the same in Netherland­ ish painting, color by color.30The text describes in detail the characteristics of each pigment, including its chemical composition, source, preparation for painting, and identification in specific works in ways understandable to a non­ specialist. The commentary in the 1997 Tech­ nical Bulletin is not as lengthy, but it does include a valuable discussion of modeling principles in reds in early Netherlandish painting and refers to common mixtures for purples and greens.The text also makes reference to painting materials mentioned in contemporary docu­ ments such as guild records.31 More specific findings by other researchers about the preparation of certain colors are also o f note. The investigations of technological sources of the period by ArieWallert have yield­ ed additional citations (with translations) from treatises on the making of pigments. Wallert’s contributions to the recent catalogue on Geertgen tot Sint Jans s Holy Kinship in the Rijksmu­ seum, Amsterdam, provide us w ith another useful introduction to the common pigments of the period, along with illustrations of some o f the methods o f production.32 In this text, we find a diagram of lead sheets coiled inside the earthenware pots used for the production o f lead white according to the “stack” or “D utch” process, and Wallert also illustrates a print from a 1545 publication showing the flasks and containers used in the production of ver­ milion in Antwerp.33 The same author, togeth­ er with Erma Hermens, has published on the production o f distilled verdigris and red and yellow lakes, although these recipes derive from a later, seventeenth-century Amsterdam manuscript.34 O ther interesting recent research deals with the prices of pigments. An article by Jo Kirby gathers pigment prices for the Renaissance period from Florence,Venice, Bruges, and En­ gland, including the London area.j5 Another, by Andreas Burmester and Christoph Krekel, cites prices for blues in Germany, mostly from the mid-to-late sixteenth century.36This would seem to be a particularly useful avenue to pur­ sue, since the information would enlarge the 6

historical context for this type o f materials research. It would also help in estimating a painter’s workshop expenses. Although archival material about pricing may not be as forth­ coming for all locales in the fifteenth and ear­ ly sixteenth centuries, the information that is available suggests that certain reds and blues were the most expensive pigments, while some o f the manufactured pigments, such as lead white, lead-tin yellow, and verdigris, were cheaper. Even a general knowledge of the rel­ ative values o f pigments opens up a manner of reading pictures that has been lost for some time, and it can help in discerning variations in quality in workshop production. There is still a great deal of diversity within this range of pigments, as well as possibilities for reidentification and expansion. Pigment particles vary in size and color, and there are of course differences in the composition, thick­ ness, and sequence of the layers in individual paintings, so that study of pigments and cross sections must be done on a case by case basis. Published illustrations of cross sections need to be in color, if at all possible, with explanatory captions. O ne key study in this regard is the comparison of the different painting materials used in two works by Dirk Bouts, one a paint­ ing primarily in linseed oil on panel and the other a TÜCHLEIN, a painting in a GLUE medi­ um on linen.37 The paint-layer structures dif­ fer in the two works, especially in that the tüchlein lacks the white chalk ground typical of panel painting.38 For the tüchlein, Bouts also used a slightly different array o f pigments: a mixture o f azurite, ultramarine, and smalt as well as indigo for blue, and chalk as well as lead white for white.39 In other studies, some pre­ viously unidentified pigments have been dis­ covered using newer methods o f laboratory analysis. One is the purple pigment fluorite. As recently as 1997, Mark R ichter and R obert Fuchs gathered published instances of fluorite in paintings, mostly for southern Germany and the Tyrol.40 In 2000, Marika Spring was able to extend these identifications to include works by a number o f Netherlandish masters active at the beginning of the sixteenth century, as well as one work by a Westphalian master.41 Some years earlier, in 1977, van Asperen de Boer had presented another newly identified pigment, a green copper sulfate with the char­

A CRITICAL OVERVIEW OF RECENT DEVELOPMENTS

acteristics of the mineral posnjakite.42 Since then, researchers have found this green in oth­ er works, but uncertainties remain as to whether the pigment was artificially produced or derived from the naturally occurring mineral. Interest­ ingly, Marika Spring has also been able to show that this green often occurs together with fluo­ rite.43The grayish blue earth avianite is anoth­ er newly identified pigment. Strictly speaking, this pigment falls outside the early Netherland­ ish period, since it has been found in paint­ ings by the seventeenth-century Dutch painter Aelbert Cuyp.44 Nonetheless, its identification, along with the previous two, suggests that we should not consider the range of pigments for this period as fixed. Significant corrections o f earlier pigment identifications have occurred as well. At the time of Coremans s study of the Ghent Altarpiece in the 1950s, it was assumed that the most wide­ spread green in Netherlandish painting was malachite, but this assumption has since been proven incorrect. The London study, for instance, found malachite in only a few works by Bouts and Gerard David.40 That malachite was used only rarely turned out to be fortu­ itous for infrared reflectography. Malachite green remains impervious to infrared fight (with the exception of detectors that can see in WAVE­ LENGTHS beyond 2 microns), and large portions of underdrawings would have remained obscured if this pigment had been in common use. The most widely used green was verdigris, a pig­ ment based on salts formed when copper sheets or filings are exposed to the fumes o f acetic acid.46 Verdigris could be further purified by distillation, but this form of the pigment may not have been used extensively.47 Scholars have often commented on the “glassy” look of par­ ticles of verdigris greens in cross sections and its consequent suitability for use as a GLAZE. In its transparent form, this green is frequently described as “copper resinate” green, the quo­ tation marks implying the assumption that verdigris was dissolved in melted resin or an oil/resin mixture. (It is now known that verdi­ gris can dissolve in the medium as part of the aging process, and this can hamper analysis.) Some researchers have even gone on to spec­ ulate that this green pigment may actually be copper resinate in crushed form.48 In this case, the viscous green mass that can be produced

Fig. 1. Image taken with a scanning electron microscope o f a particle of black chalk from an underdrawing (width o f image 29 nm).

by mixing and heating verdigris and resin would be allowed to harden, and then pulver­ ized for use as a pigment. Despite various attempts to reconstruct recipes for copper resinate, current research has yielded little evi­ dence for “true” copper resinate greens. Using FO U R IE R T R A N SFO R M -IN FR A R E D SPECTROS­ COPY ( f t - i r ), researchers have occasionally found traces of pine resin as an additive to the medium of the glaze but not to the pigment itself.49 The methods used to produce this pigment, as well as the brown discoloration that is associated with it, remain complex issues, and research into these questions continues. Even­ tually, the results of such research may contribute to our understanding of the early history of manufacturing and patterns o f trade.

While pigment analysis has resulted in new discoveries and refinements, it should be not­ ed that the identification o f underdrawing materials has lagged behind. Most identifica­ tions o f underdrawing materials are done by eye; that is, they are based on the appearance of the underdrawing in infrared documents and under the STEREOM ICROSCOPE. Underdraw­ ings that appear to be liquid and applied by brush are generally described as a dark ink, made w ith either lampblack or other burnt plant or animal matter (bone) in an aqueous medium. Dry, gritty-looking underdrawings are usually assumed to be black chalk.50 Defin­ itive identifications by analytical means have occurred only in an extremely small number

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7

of cases. A brown, ochreous underdrawing con­ taining iron has been found in a painting by Pieter Aertsen; the analysis was undertaken to explain why the underdrawing became trans­ parent in infrared.51 Two instances o f black chalk, in underdrawings by Geertgen tot Sint Jans and Jan van Scorel (fig. 1), have been con­ firmed using the elemental analysis capabilities o f the scanning electron microscope.52 Al­ though charcoal was probably used very infre­ quently in underdrawings, it has been identified in a few works by Gerard David based on its appearance in cross sections as splintery, black particles.53 Iron-gall ink underdrawing has now been confirmed in four instances and a metalpoint alloy o f lead and tin in one additional case, although almost all of these examples are Italian.54 Admittedly, the thinness of the under­ drawing layer can pose problems for techni­ cians, and there are analytical difficulties in distinguishing between carbon blacks. N one­ theless, materials analysis in coming years should pay more attention to the layout stage of paintings. Certain underdrawing materials, often in particular combinations with PRIMING or ISOLATION LAYERS, can serve to characterize workshop routines. As such studies proceed, the histories and spe­ cial characteristics of certain pigments, mix­ tures, and paint-layer structures are gradually coming into sharper focus. At the time of the Petrus Christus symposium in 1994, partici­ pants discussed an unusual use of red lead with reference to several works in the Jan van Eyck and Petrus Christus groups.55 R ed lead, or minium, is the red ubiquitous in manuscript illumination. So far it has been documented only rarely in panel painting and was not men­ tioned at all in the list o f pigments confirmed in the 1997 London study. The appearance of red lead therefore raises questions. Its use may relate to a particular function, such as the appli­ cation of reddish orange paint to frames. As dis­ cussed at the 1994 symposium, the SaintJerome in His Study in the Detroit Institute of Arts has red lead along all four of its edges where a strip frame might have been attached; Pocobene and Spronk cite a similar instance in their contri­ bution to this volume.56 Since red lead is relat­ ed to the technique of illuminators, it is worth recalling that the Detroit SaintJerome was paint­ ed on paper, not panel. While the relationship

between panel painters and illuminators and the pigments and techniques of manuscript illu­ mination are valuable topics to pursue, they lie beyond the scope of this essay. Nonetheless, it should be noted that Mark Clarke has pub­ lished an excellent review that surveys recent technical analyses o f manuscripts.57 Lead-tin yellow is another pigment that can have special significance. It is often used for the raised highlights in illusionistic depictions of metal objects or golden threads of brocades (plates 1,2). Anyone who has used the binoc­ ular microscope to study the surface o f early Netherlandish works will know that this color is often applied quite thickly and is filled with tiny, colorless inclusions. Magnified, it often looks like whipped mayonnaise. Depending pri­ marily on staining techniques, the Brussels researcher Leopold Kockaert proposed that the characteristic appearance o f lead-tin yellow results from the fact that it is an EMULSION of pigment bound in oil and a gelatin, probably made from fish glue (mayonnaise, too, is an emulsion). Kockaert claimed to have found this emulsion in other colors as well, such as reds.58 Only in the last year or so has his theory been challenged (see the end of this section). Lead-tin yellow, originally associated with the making of ceramic glazes, fell out of use by around 1750, and knowledge of the pigment was rediscovered only in 1940, at the D oerner Institute in M unich.59 Gettens then con­ firmed the identification at the Fogg in 1947.60 This gap in the history of lead-tin yellow has had its effect. Coremans suspected that most yellows in the Ghent Altarpiece were lead-tin yellow, but, as he said himself, he could not con­ firm this pigm ent’s chemical makeup, espe­ cially the tin component, with the analytical means available at the time. Nonetheless, Core­ mans proceeded to misidentify some yellow highlighting as massicot, a yellow lead oxide very rarely found in any northern painting made during this period.This led him to doubt the painted lettering as well as the gilded back­ grounds o f the panels with the Virgin, Deity, and Saint John the Baptist.61 Since then, van Asperen de Boer has suggested that these inscriptions probably contained lead-tin yel­ low and were original, and subsequent testing at Brussels proved him right.62

A CRITICAL OVERVIEW OF RECENT DEVELOPMENTS

Another example underscores the necessity o f identifying this pigment properly.The pres­ ence o f lead-tin yellow in the Eyckian Saint Jerome in Detroit was part of the evidence lead­ ing to the reinstatement of the painting as an early-fifteenth-century work. Until the Petrus Christus symposium in 1994, there were still rumors that the painting was a forgery. The research done at Detroit in preparation for the symposium included identification of pigments using the scanning electron microscope, and both lead and tin were signaled in the yellow samples.63 (When I studied the painting under the binocular microscope in August of 1994, it was also possible to discern thick strokes of yel­ low pigment containing the typical inclusions.) In this case, it is impossible to reconcile the use o f this pigment with the idea that the paint­ ing could be a forgery. The making of such a forgery before 1750 is inconceivable, so it would have to have been painted after 1940, which is impossible, since the provenance of the SaintJerome dates back to 1925.64The Fogg’s copy after Jan van Eyck’s Woman at Her Toilet presents a somewhat similar case. In her paper in this volume,Teri Hensick rightly emphasizes the detection o f lead-tin yellow in the Fogg painting. The dating and authenticity o f the panel itself are not issues, since dendro­ chronology suggests that the panel could have been executed any time after around 1511 .Yet, given the condition of this work, it is also impor­ tant to know that the remaining original pig­ ments fit with the period. A dating early in the sixteenth century is quite reasonable, in fact, for this was a time when copying of early-fifteenthcentury masters was common. In this way, Hensick’s paper is an important addition to the literature on the critique of copies, along with Pocobene and Spronk’s essay in this volume. Blues also deserve special attention.The pre­ ciousness o f ultramarine blue is well known, as testified by treatises and contracts: reports that this much-admired, deep-violet-hued blue was more costly an item than gold in fourteenthcentury Italy seem echoed years later by D iirer’s statement that the ounce o f good ultramarine he bought in Antwerp during his 1521 visit cost as much as gold.63 It is signifi­ cant, then, that this expensive pigment occurs in so many fifteenth-century Netherlandish works; it was found in more than half the paint­

ings included in London’s 1997 study.66 For the same period in Germany (with notable exceptions, as suggested by Stefan Lochner’s work), ultramarine was simply not available, and the most common blue was azurite, often o f very high quality.67 For both these blues, various grades and hues could be obtained; and, not surprisingly, it was usual to find the more expensive, more deeply colored, and more coarsely ground pigment in the upper layers or glazes, with cheaper, paler and smaller particles in the underpainting layers. Ultramarine, for instance, was often glazed over azurite.The use of ultramarine in the underlying layers of the Virgin’s blue robe in Jan van Eyck’s Annuncia­ tion in the National Gallery, Washington, is therefore unusual and is one obvious clue to the exceptional quality of the work.68 From various sources, it appears that ultramarine and azurite became more and more dif­ ficult to acquire during the sixteenth century and that other blues began to replace them. Karel van M ander noted, for instance, that a costly “beautiful blue” (mooi blauw) was not available in the Netherlands w hen Michiel Coxcie was making his copies o f the Ghent Altarpiece, and it had to be im ported from Venice.69 Exactly which blue Van Mander is referring to is unclear. It is generally assumed that he meant azurite, which became much more difficult to obtain after the conquest of Hungary by the Turks.70Yet Germany, with at least three known mines, was the main pro­ ducer of azurite in Europe around this time.71 Instrumental analysis may at some point be able to distinguish the different sources for this pig­ ment. In any case, azurite may have been less scarce than formerly thought, and less scarce than ultramarine. Jan Gossaert did paint with ultramarine, but apparently rather sparingly.72 Albrecht Dürer seems to have used this pig­ ment on only three occasions, and ultramarine has been found in the work of only a few of Dürers German contemporaries.73There was only one sixteenth-century northern N ether­ landish painter who used natural ultramarine, Jan van Scorel.74 He most likely obtained the pigment w hen he was in Venice, and even though he used it in only a few works after his return north, his supply did not last out the decade o f the 1530s. Scorel reserved the pigment for special purposes. It is found not

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9

only in the draperies of important figures in his Baptism of Christ in the Frans Halsmuseum, Haarlem, but also throughout the landscape background.There, the ultramarine on the sur­ face rests on a pink underpainting, which adds to the purplish cast o f the distant mountains (plate 3). This paint-layer structure is distinc­ tive and most likely reflects a technique Scorel learned during his stay in Italy.75 It recalls Michael Baxandall s discussion of the often sub­ tle uses o f ultramarine, and his statement, “importance is registered with a violet tinge.”76 Watching for occurrences of ultramarine will reward study. Smalt is a pigment made from ground cobaltblue glass. Although it was used increasingly in the sixteenth century and later, the National Gallery, London, has reported only a few instances of smalt in its fifteenth- and sixteenthcentury collection. One, an exceptionally early occurrence, is in the tiichlein by Dirk Bouts dat­ ed to the 1450s, while another is in Pieter Bruegel’s Adoration of the Kings, dated 1564.77 From other published examples, it appears that the decade o f the 1530s was critical for the beginning of the shift to smalt in the northern Netherlands.78 The particulars of this phenom­ enon have not yet been charted for the south­ ern Netherlands, although smalt can be assumed to have been in general use by the second half of the sixteenth century. The changes in blues during this period may have been accompanied by changes in paint-layer build-up: grayish u n d e r m o d e l i n g has sometimes been found in conjunction with this color. This would have been a way of deepening the surface color with­ out using expensive blue pigments in all the underlying layers. This practice may also relate to the simplification in paint-layer structure that has been noted for the late fifteenth and early sixteenth centuries. The presence o f a dark underlayer can often be detected first by using infrared reflectography and then studied further using the microscope and/or sampling. Blues that are opaque in infrared reflectography— that is, blues with probable undermodeling— have been found in a number of paintings, including works by Adriaan Isenbrant and Antwerp Man­ nerists such as the Master of 1518, as well as Lucas van Leyden,Joos van Cleve, and Quentin M etsys (as in the strikingly intense blue o f the Madonna’s robe in the Lamentation Altarpiece in 10

Fig. 2. Infrared reflectogram assembly showing dark undermodeling in Abraham’s robe in Herri met de Bles, Landscape with the Sacrifice of Isaac, Cincinnati Museum of Art, 1944.44. (IRR: Molly Faries)

Antwerp’s Koninklijk Museum voor Schone Künsten).79 Gray undermodeling under azurite has also been verified by infrared reflectography and cross-section analysis in a number o f works by Geertgen tot Sint Jans.80 It occurs as well under a mixture of azurite and ultramarine in theVirgin’s dress in Jan Gossaert’s Adoration of the Kings in London.81 In Gossaert’s wing panels (1521) in the Toledo Museum of Art, Toledo, Ohio, the artist used what is probably natural ultramarine over an opaque gray for portions of Saint Peter’s robe. In a Herri met de Bles land­ scape from the 1540s, smalt takes the place of the ultramarine and is painted over a grayish undermodeling in one of the foreground fig­ ures (fig. 2).82 Although this paint-layer build­ up is thus not entirely exceptional, it still seems specific enough to characterize a given painter’s workshop procedure.

A CRITICAL OVERVIEW OF RECENT DEVELOPMENTS

stockings and dark shoes, was clearly shaded with black, although the other colors o f his clothing were not (fig. 3).85 Given these exam­ ples, it is ironic that infrared reflectography is not generally thought useful for the study of paint. These examples clearly indicate that this technique can provide essential information about paint-layer structure and modeling.

Fig. 3. Infrared reflectogram digital com posite show ing m o d e lin g w ith black in Jo se p h ’s red cloak in Lucas Gassel, Landscape with the Flight into Egypt, K oninklijk M useum voor Schone K ünsten, A ntw erp, 5128. (IR R and digital com posite: M olly Faries)

Occasionally, greens are handled in a similar way: one well-known example is the dark underpainting that has been documented in the landscape background of the lower panels of the Ghent Altarpiece.83There are other exam­ ples o f this phenomenon, as in Gossaert’s Ado­ ration of the Kings, mentioned above.84 Infrared reflectography can detect related techniques, such as the addition of black to the modeling of reds, another painting practice that became more and more prominent in the six­ teenth century. In a painting attributed to Lucas Gassel Joseph’s red cloak, along with his white

For study o f the paint stage, a “low -tech” method remains essential: examination under the binocular, or stereo-, microscope, which logically belongs to an initial phase in the study of a painting. The entire paint surface can be scrutinized in magnifications of 10-30/40x or more, preliminary to other methods o f study and, o f course, before any sampling is done. Regardless of the fact that this method leads naturally to sampling and laboratory analysis o f materials, microscopic examination still allows many other types of observation that are valid from both a technical and art historical point o f view. In 1987, van Asperen de Boer and I summarized some of the possibilities of the stereomicroscope.86 Looking through the binocular eyepiece, a researcher gains a sense of the relief of the painting. A work’s condition can be ascertained, and losses, different types of CRACK patterns, and retouching can be locat­ ed. One can also observe aspects o f technique, such as thick im p a s t o as opposed to translu­ cent films, stiff or fluid strokes, juxtapositions or overlaps o f fields of color, and color mix­ tures, as well as more idiosyncratic aspects of paint handling, such as modeling techniques, and the creation of highlights and shadows. By describing what the microscope reveals, a researcher can evoke a sense o f the physical substance o f the paint and the many ways an artist can work with this malleable material. In her essay in this volume, Melanie Gifford does this extremely effectively; she refers to “thick and rounded paint” and “earth-colored paint ... swirled into ... white paint” she de­ tected in the panels of the Antwerp-Baltimore quadriptych. In another recent article, Jill Dunkerton conducted a study o f the handling properties of binding media in paints.87 In her examples, she illustrates a variety of effects, such as beaded-up strokes, sagging droplets of glaze, crisp lead-tin yellow details, indentations and scrapings in paint, blotting with the fingertips

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11

or fabric, and strokes made by brushes with either short or long hairs. Fortunately, the rich results of this method of observation can now be shared to a greater extent.There is a recent tendency in catalogues and technical studies to illustrate many more photographs taken through the microscope (for instance, plates 1 and 2). These are usually term ed P H O T O ­ MICROGRAPHS.

For medium analysis, I defer to Melanie Gif­ ford, who provides in her essay a succinct review of one of the seminal issues in the field of tech­ nical studies of early Netherlandish painting: the oil medium and its legendary association with Jan van Eyck. She also clearly elucidates several methods of testing— along with a new refinement of one method—and includes some judicious remarks about the factors that must be considered when interpreting the analyti­ cal results. Her paper and two other articles by the London researchers Ashok Roy and Ray­ m ond W hite88 stand as the most im portant recent state-of-the-field essays on medium analysis. All o f these authors have cited a num­ ber o f pre-Eyckian works from the thirteenth and fourteenth centuries that are now known to have been painted using an oil binder, many o f them R aym ond W h ite’s own identifica­ tions. Dating from around 1400, the AntwerpBaltimore quadriptych that Gifford discusses is of course also critical in this regard.The evi­ dence has built up with such consistency that some scholars are now beginning to suggest that oil represents the indigenous painting tradition o f northern Europe.89 It is generally recognized that in the field of medium analysis the London National Gallery’s record is unmatched. W hile the National Gallery’s researchers rightly acknowledge the original impetus o f Paul Coremans, Jean Thissen, and Leopold Kockaert at Brussels, they have gone on to pioneer the uses o f gas chro­ matography and GC-MS to build up more than twenty-five years o f experimental work in this field. The museum’s sampling o f forty-five paintings for medium analysis for its 1997 pub­ lication and 1998 catalogue of Netherlandish painting surely represents one o f the broadest studies of its type, and the results should by now be well known.90 London researchers have been able to distinguish the use o f different types of 12

drying oils, primarily linseed oil, as well as a more selective use o f walnut oil (sometimes together with linseed oil in the same painting), either in cold-pressed or heat-bodied form, w ith the occasional addition o f resin to the medium o f some glazes. They have also dis­ covered that medium may differ layer by lay­ er: EGG TEMPERA was not found in emulsions as some scholars expected, but was the sole binder in some underpainting layers, particularly in the Campin, Rogier van der Weyden, and Bouts groups. As data continue to come in, the over­ all results and individual variations can be inter­ preted w ith more and more subtlety. In the panels Gifford discusses in this volume, the ultramarine glaze was applied in an oil medi­ um. Ultramarine glazes in oil have now also been found in a num ber o f other London examples, as well as in R ogier van der Wey­ den’s Descent from the Cross in the Prado, Madrid.91 It appears, then, that Jan van Eyck’s technique differs in this respect. The aqueous medium that Coremans found in ultramarineblue glazes in the Ghent Altarpiece has also been confirmed in Jan van Eyck’s Annunciation in the National Gallery, Washington.92 Interestingly, the oil/glue emulsion that Kockaert identi­ fied in lead-tin yellows was not reported by the London researchers in their 1997 publication. As Gifford mentions, it may not be possible to reconcile all analytical results when different methods have been used for the research. Still, London’s sustained program o f research in this field has taken us to a new level of understanding. An area o f research that has seen a great deal o f recent activity concerns the aging of paint and the discoloration of certain pigments. Paint is, after all, not a static substance but one in which chemical changes occur as it dries and ages. The inclusions in lead-tin yellow, men­ tioned above, have recently been interpreted in some cases as metallic soaps formed by the interaction o f the pigment with the binding medium. The researchers Catherine Higgit, Marika Spring, and David Saunders further note that FT-IR could not confirm the pres­ ence of proteins in the samples they studied, thus casting doubt on the evidence Kockaert developed some years ago to postulate that an emulsion of glue and oil was used as a medium in early Netherlandish painting.93 This issue will be addressed again, one hopes, in the stud­

A CRITICAL OVERVIEW OF RECENT DEVELOPMENTS

ies of binding media that are now under way. The discoloration o f blue smalt to a grayish beige is a fairly well-known phenomenon, and it appears that the tendency of this pigment to discolor was discussed in early treatises such as those by Armenini and Karel van Mander in the late sixteenth and seventeenth centuries. These and other sources had already urged painters not to use smalt in medium-rich mix­ tures, but with a good amount o f lead white.94 The mechanics o f smalt discoloration have recently been studied by Jaap Boon and oth­ ers in the context of the Dutch MOLART and De Mayerne research programs, which support molecular studies of paint and the aging process. In addition to discerning a leaching process that depleted the potassium content of the glass, the researchers observed what they believed was the potential buffering effect o f calcium car­ bonate and lead white.95 Scholars in the con­ servation field now also regularly monitor color change in paintings, and some are developing reconstruction methods— either with actual paint or with the computer— to better under­ stand original painting techniques and tonal relationships.96 This type o f research needs to be more widely publicized, for it affects our basic reading o f pictures as well as fundamen­ tal issues related to the conservation and preser­ vation of paintings.

D en d roch ron o lo g y

Although a well-established technique in wood biology and archaeology, dendro­ chronology entered the mainstream o f early Netherlandish studies only in the mid-1980s, just at the time Peter Klein and his colleagues were announcing a Baltic provenance for the oak used in almost 100 percent of the panels painted by fifteenth- and early-sixteenthcentury Netherlandish masters.97 Before the 1970s, very little dendrochronology had been done on earlier Netherlandish paintings, with the notable exception of van Asperen de Boer’s encouragement of dendrochronological study of works by the sixteenth-century northern Netherlandish masters Lucas van Leyden and Jan van Scorel.98 At that time dendrochronol­ ogy was used far more frequently for the study o f seventeenth-century paintings, providing Rembrandt researchers, for instance, with the

unexpected information that many of the pan­ els suspected to be nineteenth-century copies were actually from Rembrandts time.99 Anoth­ er of many startling revelations concerned the painting know n as Storm at Sea (Kunsthis­ torisches Museum, Vienna), which den­ drochronology proved could not have been done by Pieter Bruegel the Elder. Art histori­ ans, confronted with these new data, have now reattributed this painting to slightly later artists, either Joos de Momper or Tobias Verhaecht.100 For the earlier period o f Netherlandish paint­ ing, these remarkable findings were matched by the discoveries that the oak support of the Eyckian SaintJerome in His Study in Detroit was integral to the painting and dated from the fifetime of Jan van Eyck,101 and that the Metro­ politan Museum of Art’s Christ Appearing to His Mother could no longer be attributed to Rogier van der Weyden but had to be by a follower. The latter example is discussed below and in the essays by Peter Klein and Maryan Ainsworth in this volume. However dramatic, these find­ ings constitute only a fraction o f the contri­ butions dendrochronology has made to the field o f early Netherlandish painting. As will be evident to the reader of this vol­ ume, Klein’s research is characterized by a will­ ingness to explain the caveats involved in using dendrochronological datings. W hat might not be as obvious is the constant refinement of the data that takes place behind the scenes. Klein has emphasized time and again that there is only one absolute date in dendrochronology. That is the date of the last ring that was growing in the wood used for the panel (this ring is sometimes called the youngest annual growth ring since it is closest in date to the present). Klein’s dat­ ings derive from this absolute. The date of this ring, with the addition of a certain minimum value to account for missing growth rings, can establish a terminus post quern for a painting, which is o f critical value to art history, as Peter Klein mentions. Other datings, such as the most likely felling date of the tree and the probable date the wood was used, also have to be esti­ mated, since, for oak, the latest extant ring on a panel is not the same as the last annual ring that was growing when the tree was cut and the wood trimmed. As the evidence shows, trimming involved the systematic removal of the SAPWOOD, a tree’s most recent growth under

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13

Fig. 4. W orm damage in sapwood in one o f the planks in the Ghent Altarpiece.

the bark. It was trimmed off with good reason, since it had more nutrients and was therefore subject to insect damage. A photograph pub­ lished by Roger Marijnissen shows the worm holes throughout a bit of sapwood that once survived in the Ghent Altarpiece (fig. 4).102 According to Klein’s published data, very few of the fifteenth-century panels he has studied have any sapwood remaining: only three from the Van Eyck/Christus/Bouts groups, four from the Rogier group, and three from the Gerard David group; no sapwood rings were found in the Memling group.103 This means, o f course, that almost every dendrochronological date for this period is an estimate based on statistical evaluations that are dependent on a number of variable factors: sapwood growth, the age of the tree, the provenance of the wood, and seasoning. Peter Klein’s ever-growing statistical base off­ sets these variables. The most pervasive refine­ ment in the data is undoubtedly the confirmation of a Baltic origin for the oak used in most Netherlandish panels. The data gathered result­ ed in a different sapwood allowance for Baltic oak than for oak from western Europe and neces­ sitated a slight shift toward the present in the derived dendrochronological dates. In confirm­ ing the Baltic provenance, core samples were tak­ en from oak trees still growing in Polish forests (see fig. 5). One can trace in Klein’s publica­ tions the gradual increase in the number of core samples, from one hundred in 1986, to two hun­ dred in 1994, to three hundred in 1998.104This fieldwork, together with the analysis of other wooden artifacts from the same region, allowed 14

Fig. 5. Drill and drill bits used for core samples taken from trees, with core samples shown in the upper left.

Klein to establish an uninterrupted master chronology for Baltic oak that covers the entire period o f early Netherlandish painting and beyond.With the constant increase in data, Klein has been able to qualify some of his previous observations. While earlier publications mention fifty to seventy-five or one hundred rings, Klein now takes the more cautious stance that it is impossible to specify an exact figure for the min­ imum number of annual growth rings required for dating.The estimates of missing sapwood and seasoning are clearly interdependent, and, by using dated works, Klein has illustrated on a case by case basis how much these figures can vary (see his table 2). Still, there has been a slight revi­ sion downward from fifteen to ten years’ sea­ soning for some fifteenth-century Netherlandish panels. This depends on the workshop and has been confirmed, for instance, for the Rogier van der Weyden group.11% at 3 microns, and an estimated 3—5% in the 1.2-3 micron region.14 Both instruments require in practice similar illumination levels for goodquality reflectograms, but this would also be affected by the type of lenses used. InGaAs cameras have a quantum efficiency o f more than 70% over the range 1.0-1.6 microns and still 50% at 0.9 micron. This amounts to a sensitivity 30 to 60 times higher than either o f the two other reflectographs. It was indeed qualitatively observed during the April 1998 demonstration that the illuminat­ ing dimmed tungsten lamp could be moved much farther away from the painting when using the 320 x 240 InGaAs camera.

SLOWLY TOWARDS IMPROVED IRR EQUIPMENT

63

NOTES

1. For these first published reflectograms, see van Asperen de Boer 1966. 2.

Taubert 1956.

3. van Asperen de Boer 1970. 4. Ibid. 5. van Asperen de Boer 1969. 6. van Asperen de Boer 1974. 7. Kobayashi et al. 1994. 8. Leech and Gutmanis 1992.

64

SLOWLY TOWARDS IMPROVED IRR EQUIPMENT

9. Walmsley et al. 1993; Walmsley et al. 1994. 10. van der Weerd, Heeren, and van Asperen de Boer 2001. 11. van Asperen de Boer 1970, 54—55, and 38, fig. 9. 12. Cohen and Olsen 1994. The authors predicted that 256 X 256 and 512 x 512 array sizes and extended-wavelength InGaAs cameras up to 2.5 microns would become available by 1995. 13. Hoffman 1998. 14. Dr.W. Cabanski, AEG Infrarot Module, Heilbronn, Germany; personal communication, 29 September 1999.

D en d roch ron ologica l A nalyses o f N e th e rla n d ish Paintings Peter Klein University o f Hamburg

Introduction

Dendrochronology, or tree-ring dating, is a method of dating wooden objects, or objects in which wood has been used, based on mea­ surements of the variation in the width of the annual growth rings of the wood.This method, a discipline belonging to the biological sciences, has been used primarily to determine the age of archaeological and architectural artifacts and structures, although it has also found a signifi­ cant application in art history in the examina­ tions of materials used in panel paintings.1 By determining the felling date o f the tree from which the panel derives, dendrochronology can ascertain, at the very least, a terminus post quern for a panel painting, i.e., the date after which the wood for the panel could have been sawed and prepared for use. This article presents a survey o f den­ drochronological findings related to N ether­ landish paintings of the fifteenth and sixteenth centuries.The biological basis of the discipline will also be discussed along with the dating pro­ cedure. Even though the fundamentals o f this method have been published elsewhere over the years,2 it is useful to review some of this information, since it has often appeared in spe­ cialized biology or conservation literature. Moreover, this information will facilitate the understanding o f the results presented in this essay.

T h e B io lo g ica l Basis o f D en d roch ron o lo g y

A tree grows both by elongation and radial increments. The elongation takes place at the terminal portions of the shoot, branches, and roots. The radial growth occurs within a spe­ cific layer of living cells called the cambium, which resides between the wood and the bark.

Cambial cells divide to produce wood cells toward the central axis o f the stem and bark cells toward the outside, resulting in an increase in thickness. Dendrochronology is concerned with the annual periodicity of a tree’s growth, which is affected by aspects of a location’s climate such as temperature and rainfall. The width of the annual growth rings will vary from year to year over the lifetime o f the tree depending on the local climatic and environmental con­ ditions. After a number o f years, the pattern o f variation in the grow th rings becomes increasingly distinctive and unique for the spe­ cific time and place in which a given tree has grown. Tree-ring structures differ for conifers and hardw ood tree species. In conifers, such as pine, fir, or spruce (fig. la), the wood is more or less uniformly composed o f one cell type, the tracheids. Hardwood trees, on the other hand, can be divided into two groups. In the first group (fig. lb), the tree rings are evident because o f an initial formation of a band of large vessels in the early wood for water con­ duction, followed by the formation o f a more compact late wood with smaller vessels and more fibers for the support of the stem. This group, which includes oak, ash, and elm, is called ring-porous. In the second group o f hardwood trees, the growth rings are more difficult to discern (fig. lc), because the ves­ sels are uniformly distributed throughout the tree ring; the only demarcation between the successive growth layers is an increase in fibers toward the end o f the growth period, similar to that seen in ring-porous trees.The trees in this second group are called diffuse-porous and include beech, limewood (also known as linden), maple, and poplar. Finally, trees grow­ ing in the subtropics and tropics exhibit no distinct manifestation o f grow th-ring zones DENDROCHRONOLOGICAL ANALYSES

65

a. Spruce (Picea abies).

b. Oak (Quercus petraea).

c. Limewood (Tilia ssp.).

d. Tropical wood (Hopea bmchyptea).

Fig. 1. Photomicrographs o f different species o f wood in cross section.

66

DENDRO CHRONOLOGICA L ANALYSES

|/v v au

nva^ w /í

iwvA^vvyvv-^vH

[vwv^Vv'A A W V 'I w s

1900

ü5S—

T

5

^

- T

r

t

f

k v NA/vW V ^ V t| 1500

v

v

rvywv^ r y\ / v/ ,j

|/NvVvV ^ W ^ vrvl êoõ

^

Fig. 2. Overlap system for establishing master chronologies.

(fig. Id), but they sometimes form zonal lay­ ers, akin to, but not identical with, real growth rings. Mahogany and rosewood are examples o f this type o f tree. Therefore, only wood from trees in temper­ ate zones can be dated by means o f dendrochronology.The biological regularity of the tree-ring pattern allows dating by comparing the growth sequences of undated wood with those o f wood of known age and location. In order to set up continuous dated sequences for periods longer than one tree’s lifetime, it is nec­ essary to overlap individual curves to establish master chronologies.These are created empir­ ically, region for region, beginning with trees still living in forests whose last annual growth ring is self-evidently the current year. Then samples are taken from manmade objects, working progressively backward in time to find examples whose later growth rings overlap and synchronize with the early growth rings o f the firmly dated sequence (fig. 2).This process is called “bridging.” The master chronology for

oak wood from the Baltic region, which is so im portant for Netherlandish paintings, was established in this way and runs an impressive 990 years.

M easuring and C ross-D atin g

Ring widths in panel paintings are measured directly on the panel. If necessary, a thin line along the back of the panel’s edge is cleaned by removing the varnish or by scrapping off paint layers to make the rings visible. For measure­ ments taken on site without laboratory equip­ ment, a measuring loupe is used and values are recorded manually. It is, however, much more convenient to take measurements in the labo­ ratory using a device connected to a comput­ er. The measurements are then recorded immediately for the subsequent steps o f the analysis. Originally, measurement sequences were compared visually, using hand-drawn graphs DENDROCHRONOLOGICAL ANALYSES

67

that were overlaid and matched. While visual comparison is still essential in matching and comparing, statistical values for the width of particular rings can help in establishing the degree o f closeness in the synchronization of the curves. This reduces the time needed for comparison to a small fraction of what was for­ merly required. For the dating of a growth-ring sequence, a minim um num ber o f rings is

required to obtain reliable results. U nfortu­ nately, it is not possible to establish an absolute figure for this threshold. Sometimes even curves considered “long” do not contain the neces­ sary characteristic pattern required for unam­ biguous dating. Since many factors are involved, it is sometimes possible to arrive at a dating with as few as fifty tree rings. O n other occa­ sions, two hundred tree rings may not be sufficient.

E stim ation o f S ap w ood G rowth and Seasoning

The critical piece o f dendrochronological information for art history is the felling date of the tree. If the last ring under the bark has been preserved, it can provide the exact year, and even the season, in which a tree was cut. How­ ever, when woodworkers prepared oak for pan­ el paintings, they usually cut the planks radially, relative to the cross section of the tree (figs. 3a and b).They also trimmed off the bark and the light, perishable sapwood (fig. 3c), thereby elim­ inating the evidence o f the last (i.e., youngest)

Fig. 3a. Cross section o f oak.

Fig. 3b.Various cuts for extracting boards for the con­ struction o f a panel.

68

DENDROCHRONOLOGICAL ANALYSES

1371

1619

1614

1430

Fig. 3c. Sample o f two boards glued together in a panel, with the sapwood cut off and the younger edges of the boards adjoining one another at center.

Fig. 4b. N um bers o f sapwood rings in oak trees from northern Poland.

Fig. 4a. Natural distribution o f oak in Europe. Quercus robur L. (European oak) is found within the area demar­ cated by the solid line; Quercus petraea Liebl. (sessile oak) is found south and west o f the broken line. The arrows trace the movement o f oak timber from its Baltic source to the locations where it was used in panels.

rings and making an exact determination o f the felling date impossible. Thus, only the last extant, measured growth ring on the panel can be dated to an exact year. Nevertheless, statis­ tical evaluation applied on a case by case basis can provide an estimate o f the number of miss­ ing sapwood rings that must be added to the date of the last ring. The estimate depends not only on the number of sapwood rings relative to the tree’s age but also on the provenance of the wood.The export of timber from the Baltic region*5and from Riga4 has now been studied (fig. 4a). From these and similar studies, we know that the number of oak sapwood rings can vary from the western regions of Europe to eastern regions. The number of oak sapwood rings found in trees from the Baltic varies between 9 and 36, with a median o f 15 (fig. 4b). For wood originating in Germany or the Netherlands, the median value is 17, w ith a minimum of 7 and a maximum o f 50.5 W hen the execution date o f a painting is definitively known from art historical research,

the determination of the felling date can pro­ vide information about the amount o f time the wood was seasoned before use. For oak panels from the sixteenth and seventeenth cen­ tury, the interval between the felling o f the tree and the creation o f a painting has been determined in most cases to be from 2 to 8 years.6The limited number of studies of signed and dated fifteenth-century panels does not yet permit such a close estimate.7 Instead, cur­ rent investigations of this period suggest a sea­ soning time anywhere from 10 to 15 years, a finding that corresponds w ith analyses o f fifteenth-century panels attributed to Cologne masters.8 It has also become apparent that the length of seasoning can vary from workshop to work­ shop (see table 2; abbreviations used in figures and tables are explained in table 1). Problems develop because the unknown total number o f sapwood rings precludes an exact deter­ mination of the amount of time the wood was seasoned. This is complicated further by the fact that these estimates rest on the assump­ tion that it was only the sapwood that was trim m ed. Every additional heartw ood ring that was cut off would also affect the estimate o f seasoning. W ith panels in the R ogier van der Weyden group, the calculated average number o f 15 added sapwood rings plus 10 years o f seasoning resulted in estimated dates that correspond fairly well to art historical dating.9 DENDROCHRONOLOGICAL ANALYSES

69

AR

Am sterdam , Rijksmuseum

AN

A n tw e rp , Museum Mayer van den Bergh

ASL

Aachen, Suerm ondt Ludwig Museum

B

Berlin, Staatliche Museen zu Berlin, Preußischer Kulturbesitz, Gemäldegalerie

BUD

Budapest, Szépmûvészeti M úzeum

CAM

C am brid ge , Mass., Harvard U niversity A rt M useum s, Fogg A rt M useum , Busch-Reisinger Museum

CH-RIG

Riggisberg, A begg -S tiftun g

CHI

Chicago, A rt Institute o f Chicago

CLE

Cleveland, Cleveland Museum o f A rt

DG

Dresden, Gemäldegalerie

FS

Frankfurt am M ain, Städelsches K unstinstitut

GEN

Geneva, Musée d 'A rt et d'HIstoire

GRA

Granada, Capilla Real

HHK

Ham burg, Ham burger Kunsthalle

LIS

Lisbon, Museu Nacional de A rte A ntig a

LN

London, National Gallery

LPZ

Leipzig, Museum der Bildenden Künste

MA

M adrid, Museo del Prado

NY

New York, M etrop olitan M useum o f A rt

PHI

Philadelphia, Philadelphia Museum o f A rt

PL

Paris, Musée du Louvre

ROT

Rotterdam, Museum Boijm ansVan Beuningen

SAR

Sarasota, John and M able Ringllng Museum o f A rt

TOL

Toledo, Toledo Museum o f A rt

WN

W ashington, D.C., National Gallery o f A rt

Table 1. Abbreviations for locations used in figures and tables.

seasoning tim e (years) w ith a Dated w orks by fifteenth-century painters

last

m inim um o f

m edian o f

m axim um o f

(youngest)

9 sapwood

15 sapwood

36 sapwood

g ro w th ring

rings

rings

rings

D. Bouts, P o rtra it o f a M a n , 1462. (LN; 943)

1436

17

11

-

P. Christus, Virgin a n d C hild w ith St.

1421

27

21

0

1409

16

10

1411

17

11

1415

35

29

w ith location and inventory num ber

Hieronymus a n d St. Francis, 1457. (FS; 920)

J. Daret, The V isitation and The A d o ra tio n o f th e M a g i, 1434/35. (B; 542, 527)

J. van Eyck, Virgin a n d C hild in a Church, 1437. (DG; 799) S. M arm ion, St. B ertin A lta rp ie ce , 1459. (B; 1645)

Table 2. Seasoning time o f oak boards in relation to the number o f sapwood rings.

70

DENDROCHRONOLOGICAL ANALYSES

8

Fig. 5. Dendrochronological datings o f the three boards (I, II, III) o fjan van Eycks Rolin Madonna. The dates indi­ cate the last measured (youngest) heartwood ring.

In the case ofjan van Eyck’s Rolin Madonna (Musée du Louvre, Paris), the mean values relat­ ed to sapwood and seasoning could lead to a misinterpretation: that an attribution to Van Eyck would be impossible. The last extant heartwood ring on the panel dates to the year 1417 (fig. 5). By estimating a minimum o f 9 sapwood rings and a minimum of 2 years’ sea­ soning, one can arrive at a date for the earliest possible creation o f the work of 1428. W hen using the mean values of 15 sapwood rings and 10 years of seasoning, the estimated date of the painting’s execution becomes 1442, one year after Van Eyck’s death. In fact, the only hard proof dendrochronology can offer is that the execution of the painting cannot have occurred before 1428 (the last measured tree ring on the panel plus a minimum o f 9 sapwood rings and a minimum o f 2 years’ seasoning). Since the wood in this case derives from a tree about 200 years old and therefore a greater number of sapwood rings than the minimum is likely, the cre­ ation date o f the Rolin Madonna seems more plausible in the mid-1430s than at the end of the 1420s.

D en d ro ch ro n o lo g ica l D a tin g o f Oak Panels

Despite the problems related to the deter­ mination of the felling date o f a tree and the number o f years o f seasoning for the wood, dendrochronology can be an important factor in art historical dating and attribution. How­ ever, only when the felling date is later than the art historical date must the dendrochronolog­ ical result take precedence, since that method provides concrete evidence that the art his­ torical date is incorrect. If the felling date is earlier than art historical opinion, other pos­ sibilities must be considered: the board may have been cut from the center of the tree, the wood may have been seasoned for a long time, or the art historical dating may be too late. In these cases, dendrochronology cannot provide the definitive date for a painting. The analysis o f a group o f panels from one workshop is far more helpful in problems of attribution and date than the analysis of a sin­ gle panel painting. Since 1968, the departDENDROCHRONOLOGICAL ANALYSES

71

group

num ber o f

num ber o f

analyzed panels

analyzed boards

Aertsen, P.

13

41

Bosch, H.

82

230

Bouts, D. and A.

42

76

Bruegel, P.

15

35

Cam pin, R.

31

68

Christus, P.

18

35

Cleve, J. van

41

107

Daret, J.

2

7

David, G.

42

74

Eyck, J. van

24

39

Flandes, J. de

7

11

12

24

Heemskerck, M. van

17

42

Leyden, A. and L.

17

46

M arm ion, S.

6

21

M em ling, H.

26

43

Metsys, Q.

14

22

7

14

Gossaert, J.

O ostsanen*, J.C. van Orley, B. van

10

25

Patenler, J.

16

21

Provoost, J.

11

22

Scorel*, J. van

29

79

W eyden, R. van der

67

174

Table 3. Early Netherlandish panels analyzed with dendrochronology. *These numbers do not reflect the recent reattribution o f the Chicago Adoration of the Magi (1935.381) from Jacob Cornelisz van Oostsanen to Jan van Scorel. See Faries andW olff 1996.

m ent o f dendrochronology at the Universi­ ty of Hamburg has collected dendrochronological data from over 2,500 panel paintings from different countries and periods.Table 3 shows a list o f some Netherlandish painters and their followers and the number o f ana­ lyzed panels. In addition to the listed painters and their followers, many paintings by anony­ mous masters and masters nam ed w ith a sobriquet have been studied. All attributions

to painters an d /o r their followers mentioned here derive from the museums or the p ri­ vate owners. The discussion that follows will demonstrate the varying possibilities that dendrochronolo­ gy offers for fifteenth- and sixteenth-century oak panels. Oak was used almost w ithout exception for the wooden supports o f paint­ ings in the northern regions of west and mid-

painter

title , location, and inventory num ber

w o o d species

Lucas van Leyden fo llo w e r

The C ard Players (WN; 1961.9.27)

linden ( Tilia ssp.)

Master o f the Legend o f

V irg in a n d C h ild (ROT; 2481)

f ir (A b ie s alba)

Jan van Scorel*

A d o ra tio n o f th e M a g i (CHI; 1935.381)

fir (A b ie s alba)

Jan van Scorel (attr.)

D y in g C le o p a tra (AR; A2843)

beech (Fagus ssp.)

the M agdalen (?)

Table 4. Early Netherlandish panel paintings on wood other than oak. *Previously attributed to Jacob Cornelisz van Oostsanen. See Faries andW olff 1996.

72

DENDROCHRONOLOGICAL ANALYSES

Jan v a n Eyck F o llo w e rs

1451

1452

1459

1469

1478

C h r is t B e a r in g t h e C r o s s ( B U D ; 2 5 3 1 ) , III

O

1481

s a m e tre e

rm Baltic 1494

1200

1250

1300

1350

1400

1450

1500

1550

Fig. 6. D endrochronological datings o f various paintings by followers o f Jan van E y ck .T h e dates indicate the last measured (youngest) heartw ood rings. R o m an numerals refer to different boards in the same painting.

die Europe during the fifteenth and sixteenth centuries, and it was imported almost exclu­ sively from the Baltic region during that time. To date, only a few paintings by Netherlandish masters have been identified that were not exe­ cuted on oak supports (see table 4). In works by followers of Jan van Eyck, den­ drochronological analyses have helped to dif­ ferentiate between an original painting and later copies. The felling dates of the trees used for the paintings listed in figure 6 have led to attri­ butions and datings after the death of Jan van Eyck. Adding the mean values for sapwood and seasoning time to the felling dates leads to the conclusion that the Christ Bearing the Cross (Museum of Fine Arts, Budapest) and the Woman at Her Toilet (Harvard University Art Museums, Cambridge, Massachusetts) were executed at the beginning of the sixteenth century. It is also possible, by means o f den­ drochronology, to establish that wooden planks

in the same or different paintings derive from the same tree. W hen the growth-ring curves are identical, the boards must have been cut from the same tree. Although it is not neces­ sarily the case, it seems plausible to assume that artists in a particular workshop used boards from the same tree.This proved true in three Eyckian paintings, the Giovanni Arnolfini and the Baudouin de Lannoy (both Gemäldegalerie, Berlin) and the Stigmatization of Saint Francis (Philadelphia Museum of Art). A comparison of the tree-ring curves from the three samples showed that the plank for the Stigmatization was cut from the same tree as the other two but more toward the center.10 By comparing the tree-ring curves of paint­ ings by Juan de Flandes (fig. 7), it was deter­ mined that the boards for the panels derive from two trees. The paintings in question are John the Baptist (Musée d’Art et d’Histoire, Geneva), the Banquet of Herod (Museum May­ er van den Bergh, Antwerp), and the Birth of DENDROCHRONOLOGICAL ANALYSES

73

Fig. 7. Dendrochronological datings o f paintings by Juan de Flandes and a follower of Rogier van der Weyden (Juan de Flandes?).The dates indicate the last measured (youngest) heartwood rings. R om an numerals refer to different boards in the same painting.

Saint John the Baptist (Cleveland Museum of Art), which were measured by three different dendrochronologists.11 Further analysis of these curves led to the surprising realization that the same growth-ring characteristics were present in the Mary Altarpiece, now attributed to a follower o f R ogier van der Weyden. The left wing and middle panel o f this altarpiece (Capilla Real, Granada) and the right wing (M etropolitan M useum o f Art, N ew York) derive from one o f these two trees.12 Since the wood exhibited a growth-ring structure typical of trees from the Baltic region, we can conclude that there must have been a trans­ port o f Baltic wood to Spain at the end of the fifteenth century. R ecent evaluations of oak panels painted by Portuguese masters active at the beginning o f the sixteenth century have also confirmed the shipping o f Baltic wood to Portugal.13 The attribution o f boards to the same tree has also been demonstrated for paintings by 74

DENDROCHRONOLOGICAL ANALYSES

Rogier van der Weyden or his workshop (fig. 8). The wood o f the Visitation (Museum der Bildenden Künste, Leipzig) has the same tree­ ring characteristics as three boards used in the support o f the Crucifixion Triptych (AbeggStiftung, Riggisberg). Moreover, in the plank from the Visitation, sapwood rings were found. This is a very rare phenomenon for the fifteenth century and allows a much more accurate determination o f the felling date o f the tree used for this painting. Dendrochronology can also make a chrono­ logical differentiation among copies o f the same composition painted within a workshop (fig. 9).The composition known as the Madon­ na in the Apse is thought to derive from the workshop o f R o b ert Cam pin and exists in many versions. Examination of the youngest growth rings (the rings that grew last) o f the panels studied makes it clear that all o f these works could only have been painted by fol­ lowers o f Campin in the third quarter o f the

R o g ie r v a n d e r W e y d e n ( 1 3 9 9 /1 4 0 0 - 1 4 6 4 )

C r u c if ix io n - T r ip ty c h ( C H - R I G ) , c e n t e r , II

C r u c if ix io n - T r ip ty c h ( C H - R IG ) , c e n te r, I

□

V is ita t io n (L P Z ; 1 5 5 0 )

O

1416

O

1416

♦

1422

C r u c if ix io n - T r ip ty c h ( C H - R I G ) , le ft w in g , II

C r u c if ix io n - T r ip ty c h , [T

♦

( C H - R I G ) , r ig h t w in g , I |_[

1413

C r u c if ix io n O

♦

T r ip ty c h

= s a m e tre e

1412

(C H -R IG ), r ig h t w in g , II

M Baltic sapwood

C r u c if ix io n - T r ip ty c h ] ( C H - R I G ) , c e n t e r , III

h 1150

+ 1250

J

❖

1406

— I—

1350

1450

Fig. 8. Dendrochronological datings o f paintings by R ogier van der Weyden. The dates indicate the last measured (youngest) rings. R om an numerals refer to different boards in the same painting.

Fig. 9. Dendrochronological datings of paintings o f the Madonna in the Apse by followers o f Robert Campin. The dates indicate the last measured (youngest) heartwood rings. Roman numerals refer to different boards in the same painting.

DENDROCHRONOLOGICAL ANALYSES

75

Fig. 10. Dendrochronological datings o f the Adoration of the Magi by Hieronymus Bosch and followers. The dates indicate the last measured (youngest) rings.

H ie ro n y m u s Bosch (c .1 4 5 0 - 1 5 1 6 ), T h e H a y w a g o n

MA; 2 0 5 2 , III

HQ

1250

B a ltic

1499

1350

1450

1550

Fig. 11. Dendrochronological datings o f The Haywagon by Hieronymus Bosch.The date shows the last measured (youngest) heartwood ring. R om an numerals refer to different boards.

76

DENDROCHRONOLOGICAL ANALYSES

M a s te r o f t h e St. Joh n A lta rp ie c e

□

O

= s a m e tre e

A ll b o a r d s o r i g in a t e d in t h e B a lt ic r e g i o n .

1200

1250

1300

1350

1400

1450

1500

1550

Fig. 12. D endrochronological datings o f three paintings by the M aster o f the S t.John Altarpiece. T h e dates indicate the last measured (youngest) heartw ood rings. R o m an numerals refer to different boards in the same painting.

fifteenth century or in the beginning o f the sixteenth century. W hen dendrochronological examinations were performed on various versions of the Ado­ ration of the Magi by Bosch or his followers (fig. 10), it was determined that only the New York and Philadelphia panels could have been painted in the lifetime of Hieronymus Bosch. Even so, this information does not necessitate an attribution to the master; that authentica­ tion can only be made by art historians. The analysis did tell us that the version of this com­ position in Aachen could only have been cre­ ated toward the middle of the sixteenth century, and another painting of this subject in a pri­ vate collection is a copy from the seventeenth century.14 A nother work associated with Bosch, the well-known Haywagon (Museo del Prado, Madrid), has a youngest ring dating to 1499 (fig. 11).Thus, the earliest possible felling date of the tree used would be 1508, still within the lifetime o f Hieronymus Bosch. It would be

interesting to compare that felling date with the felling date of the other version of this com­ position in the Monasterio de San Lorenzo, Escorial. Such a comparison might reveal which of the two works was created first. We also examined boards from three paint­ ings by the Master of the Saint John Altarpiece (fig. 12): Saint John Preaching (Philadelphia Museum o f Art), The Birth of Saint John, and Elizabeth Fleeing with Her Son (both in the M useum BoijmansVan Beuningen, R o tte r­ dam). In total, nine planks were examined, and it was determined that these planks originated from three trees.The youngest measured heartwood ring (1495) was observed in the two R otterdam paintings. The boards o f the Philadelphia Saint John Preaching were not ful­ ly measured because their edges have been damaged; thus, these boards exhibit a smaller number of rings. Lastly, figures 13-15 show the youngest rings o f the planks from various paintings in the Jan Provoost group. The interpretation DENDROCHRONOLOGICAL ANALYSES

77

A n o n y m o u s S o u th N e th e rla n d is h M a s te r a n d Jan P ro v o o s t (c. 1 4 6 5 - 1 5 2 9 ) A n o n y m o u s S o u th N e th e r la n d is h m a s te r , C r u c ifix io n ( fo r m e r ly a ttr. to

1446

J a n P r o v o o s t) (R O T ; 2 4 7 7 )

Im iu iiiiiiiiii J a n P r o v o o s t, T h e D is p u te o f S t. C a th e r in e

O

1484

(R O T ; 1 6 8 2 ), I lllllllllllllllll

llllllllllllllllll J a n P r o v o o s t, T h e D is p u te o f S t. C a th e r in e

O

1486

( R O T ; 1 6 8 2 ) , II

Trmn11unimi O = s a m e tre e

1200

1300

1400

1500

Fig. 13. Dendrochronological datings o f the Crucifixion by an anonymous South Netherlandish master (formerly attributed to Jan Provoost) and The Disputation of Saint Catherine of Alexandria by Jan Provoost.The dates indicate the last measured (youngest) heartwood rings. Rom an numerals refer to different boards in the same painting.

Fig. 14. Dendrochronological datings o f a Virgin and Child by an anonymous South Netherlandish master (for­ merly attributed to Jan Provoost) and two paintings by Jan Provoost. The dates indicate the last measured (youngest) heartw ood rings. R om an numerals refer to different boards in the same painting.

78

DENDROCHRONOLOGICAL ANALYSES

Fig. 15. D endrochronological datings o f the panel and the frame o f th e Fogg A rt M u seu m ’s Last Judgment by Jan Provoost.The dates indicate the last measured (youngest) heartw ood rings. R o m an numerals refer to different boards in the same painting.

o f the dating can be carried out only by art historians, since the differences in felling dates do not dictate either an early or a late art his­ torical date.15 In one case (fig. 15), it was pos­ sible to show that the wood for the frame had the same date o f origin as the planks. This phenom enon is very rare because the num ­ ber of tree rings on a frame is usually not suf­ ficient for dating.

C onclu sion

Results of dendrochronological investigations such as those discussed above demonstrate that a terminus post quem can be established for the

execution of pan el paintings. Table 5 shows the results o f dendrochronological analysis for a number of Netherlandish paintings in the col­ lections of the Harvard University Art Muse­ ums. This exact dating, however, applies only to the last growth ring on the panel. Other fac­ tors can vary considerably, such as the amount of time that wood was seasoned and the pos­ sibility that differing numbers o f tree rings might have been cut off during preparation of the wood for use. Differences that arise between information gleaned from the last-measured ring on the panel and the art historical date and attribution o f a painting reflect the possibilities and limitations of using dendrochronology in dating panel paintings.

DENDROCHRONOLOGICAL ANALYSES

79

painter

title and

wood

number of

dates of

earliest

plausible

inventory number

species

boards and

growth rings

felling date

felling date

and origin

growth rings

(minimum of

(median of

9 sapwood rings)

15 sapwood rings)

Anonymous

Anonymous

A. Bouts

A. Bouts

Christ in the Garden o f

oak,

Gethsemane, 2001.193

Baltic

A rre st o f Christ,

oak,

BR52.15

Baltic

M a n o f Sorrows,

oak,

2001.170

Baltic

M a te r Dolorosa,

oak.

2001.171

Baltic

G. David

D o n o r a n d Bishop Saint,

oak,

follower

1906.6B

Baltic

J. van Eyck

W om an a t H er Toilet,

oak,

follower

1969.83

Baltic

1:171

1488-1318

1501a

1507

I: 177

1492-1316

1501a

1507

I: 207

1467-1261

1478b

1484

I: 208

1469-1262

1478b

1484

I: 290

1468-1179

1477

1483

I: 123

1494-1372

1503

1509

1532

1538

1495

1501

Master of

P ortrait o f a M an,

oak,

I: 241

1523-1283

the 1540s

2001.169

Baltic

II: 71

no dating

Master of the

Saint Luke Painting the

oak,

I: 60

no dating

Holy Blood

Virgin, 1910.6

Baltic

II: 142

no dating

Jan Provoost

Last Judgm ent, 1997.2

oak.

I: 101

1472-1372

Baltic

II: 126

1486-1361

III: 159

1485-1327

IV: 177

1486-1310

frame I: 82

1473-1392

frame II: 95

1485-1391

Table 5. Fifteenth- and sixteenth-century paintings in the collections o f the Harvard University Art Museums (Fogg Art M useum and Busch-Reisinger Museum) examined with dendrochronology. a The boards of Christ in the Garden of Gethsemane and the Arrest of Christ were made from the same tree. The youngest growth ring o f the Arrest of Christ dates to 1492. b The boards o f the Man of Sorrows and Mater Dolorosa were made from the same tree.The youngest growth ring of the Mater Dolorosa dates to 1469.

80

DENDROCHRONOLOGICAL ANALYSES

NOTES

1. Bauch, Eckstein, and Brauner 1978; Fletcher 1978;Baillie 1984; Eckstein et al. 1986; Schweingruber 1988; Klein 1991; Klein 1993; Vynckier 1993; Hillam andTyers 1995; Lavier and Lambert 1996. 2. Klein 1995a; 1996a; 1997a; 1998b. 3. Eckstein et al. 1986;Wazny and Eckstein 1987; Baillie 1982; Bonde 1992. 4. Zünde 1999. 5. Hollstein 1980; Baillie 1982; Eckstein et al. 1986; Kuniholm and Striker 1987;Wazny 1990. 6. Bauch, Eckstein, and Brauner 1978. 7. E.g„ Klein 1991.

8. Bauch, Eckstein, and Klein 1990. 9. Kemperdick and Klein 1997. 10. Klein 1997b. 11. The examinations were performed by Alain Orcei (Geneva),Jozef Vynckier (Antwerp), and Peter Klein (Cleve­ land) . 12. Périer d’Ieteren et al. 1993. 13. Esteves and Klein 1999. 14. Editor’s comment: Faries and van Asperen de Boer 1997 dated the Aachen painting at c. 1540. 15. Compare Spronk 1999.

DENDROCHRONOLOGICAL ANALYSES

81

T he F o g g 5§ C opy after a Lost Van Eyck: C onservation H istory, R ecen t T reatm ent, and T echnical E xam in ation o f the Woman at H er Toilet Teri Hensick Harvard University A r t M useums

Introduction

Edward W. Forbes, director o f the Fogg from 1909 to 1944, often acquired unfinished paint­ ings and works in problematic condition for the museum’s collection. He actively sought minor works for the conservation department, founded in 1927, to study painters’ materials and techniques and to test new varnishes or inpainting practices. Generations o f students learned to discriminate, by observation and by technical means, the work of a restorer from that of a master.1 In this tradition, the Woman at Her Toilet (plate 6), was a logical addition to the Fogg’s collection. More than 25 percent of the paint surface of this work is lost, and what remains of the original paint is so heavily abrad­ ed that the work has been dubbed the “Van Eyck wreck.” Although a full range of techni­ cal analyses has been performed on this work, uncertainties persist today about which aspects of it are original and which are not. How, or indeed whether, to exhibit the painting has been a recurring issue. Nevertheless, it remains one of the Harvard University Art Museums’ more frequently reproduced paintings, having intrigued scholars by its subject matter and its connection to a lost work by Jan van Eyck.The panel’s provenance can be traced back only to the collection of the English artist Augustus John (1878—1961). From there, it passed to his wife and then through the Boston art dealer R obert Light to the Fogg in 1969. The Woman at Her Toilet depicts two women standing side by side, one nude and the other clothed in a red dress.The nude wears red san­ dals and holds a towel in her proper left hand, her right hand poised above a basin. The fig­ ure in red, her hair pulled into horns held by

a black net and covered with a folded white cloth, holds a fruit in her proper right hand and a glass carafe in her left. A gold chain drapes across her somewhat protruding stomach, and a black bag (or tassel) hangs from a cord on the side of her dress. A bed stands in the right back­ ground of the chamber, draped with a dark blue curtain and fringe. W hite bedclothes are par­ tially visible on either side o f the curtain. A window at the left side of the room allows light in; the window frame is divided vertically by a mullion with a black metal catch to secure the shutters and horizontally by another mullion near the top edge o f the painting. A convex mirror hanging on the window reflects the side and front of the two figures. Another piece of fruit sits on the windowsill above a small chest. A basin rests, along with a small comb, on top of the chest. A folding chair and a pair of wood­ en pattens rest on the floor in the lower left. A small dog appears in the lower center o f the gray tiled (or stone) floor. Directly behind the two women is a high-backed chair with carv­ ing along the top and a blue seat cushion.The footrest o f the chair supports a small blue vessel. A raised barb on the recto suggests that the panel may once have had an engaged frame. The verso o f the panel is painted green and brown to imitate marble. Two horizontal chis­ eled grooves made to hold cross-battens, which have since been removed, interrupt the mar­ bling (plate 7). Until recently, the Woman at Her Toilet was generally thought to be a contemporary or fifteenth-century copy of a lost Van Eyck.The same composition appears in a 1628 painting, now at the Rubenshuis in Antwerp, depicting THE FOGG’S COPY AFTER A LOST VAN EYCK

83

Fig. 1. Willem van Haecht, The Cabinet of Cornelis van der Gheest, 1628. Wood, 104 x 139 cm. Rubenshuis, Antwerp, S171.The arrow indicates the lost composition by Van Eyck.

the collection o f Cornelis van der Gheest (fig. I).2 In his 1638 will,Van der Gheest, a prominent Antwerp collector, listed this work as a painting by Van Eyck. The Cabinet of Cor­ nelis van der Gheest was painted by Willem van Haecht, who was also the curator o f the Van der Gheest collection. In figure 1, the painting o f the Woman at Her Toilet is indicated by an arrow; plate 8a shows the picture in detail.Van Haecht’s version is similar to the Fogg work, although the distortions caused by perspectival foreshortening make it difficult to compare the two. Plate 8b shows the Van Haecht detail after digital manipulation to eliminate some of the effects of foreshortening.3 Reworking the detail in this way has provided useful clues for reconstructing the missing parts o f the Fogg painting, as described below in the section on conservation and examination. The two works differ in scale. The hypo­ thetical size (c. 90 x 60 cm)4 of the Woman at 84

THE FOGG’S COPY AFTER A LOST VAN EYCK

Her Toilet in the Van Haecht painting is rough­ ly four times higher and wider than the Fogg panel, which measures 27.5 x 16.5 cm. There are also discrepancies in m inor details. The comb on the table in front of the basin in the Fogg painting does not appear in the Van Haecht work. Its absence may be due to retouching along the panel jo in that runs through Van Haecht’s Woman at Her Toilet (see plate 8b).The bed curtain is handled differently in the two compositions, possibly due to reworking in this area of the Fogg painting. The versions differ in painting style and technique as well, reflecting general differences between sixteenth- and seventeenth-century painting practice.Van Haecht’s figures look decidedly more voluminous than the angular and atten­ uated figures in the Fogg panel. The top paint layers throughout Van Haecht’s painting appear to lie over a striated impiumatura layer, while the Fogg work is painted directly on a light ground.

The assumption that Van Eyck painted the original version o f the Woman at Her Toilet is based in part on Bartolomeo Fazio’s 1456 description o f paintings in the collection of Ottaviano della Carda. Fazio describes paint­ ings by Van Eyck o f “women o f uncommon beauty emerging from the bath.”5 In the Van Eyck literature, widely differing interpretations, ranging from secular to biblical subject matter, have been offered for the Woman at Her Toilet. For example, some scholars have interpreted the Woman at Her Toilet as a nuptial bath scene6 or as an allegory of Vanitas.7 Others have iden­ tified the bather as Judith8 and as Bathsheba.9 The work has also been linked to Van Eyck’s famous Portrait of Giovanni(?) Arnolfini and His Wife (fig. 2). MaxJ. Friedländer noted the cor­ relation between the projected size o f the Woman at Her Toilet in the Van Haecht paint­ ing and the dimensions o f the Arnolfini dou­ ble portrait.10 Julius Field thought that the original panel could have functioned as a cov­ er or sliding lid for the Arnolfini painting;11 documents from as early as 1516, however, describe the Arnolfini double portrait as hav­ ing two wings, rather than a lid.12 The presumed close relationship w ith the Arnolfini double portrait has strongly influ­ enced art historical discussion of the iconog­ raphy o f the Woman at Her Toilet. Field emphasized the similarity between the overall plans of the interiors and the many details com­ mon to both paintings.13 In particular, he not­ ed the little dog, the pattens in the lower left, the convex mirror, the chest, the high-backed chair, and the foreshortened celling beams.Two other strikingly similar details recently noted by the author of this essay are the red sandals worn by the nude, similar to those in the back­ ground o f the Arnolfini double portrait, and the window shutter clasp in the upper part of the mullion in both works.14 Held, believing the Arnolfini painting to be a marriage por­ trait, suggested that the Woman at Her Toilet depicted the ritual bath o f bride Giovanna Cenami with a friend, possibly Margaret van Eyck, standing beside her as an attendant.15 Lome Campbell, who has recently argued that the Arnolfini double painting is not a mar­ riage portrait, also rejects the interpretation that the Woman at Her Toilet is an image of a

Fig. 2. Jan van Eyck, Portrait o f Giovanni(?) Arnolfini and His Wife, 1434. Oil on oak panel, 84.5 x 62.5 cm .The National Gallery, London, NG186.

nuptial preparation. According to Campbell, the similarities described above are “proba­ bly coincidental.” 16

Present C on d itio n o f the Painting

The extremely poor condition of the Woman at Her Toilet confounds a clear reading o f the painting (fig. 3). Large losses and scattered small­ er losses are found in the forehead, nose, neck, thighs, left calf, right shoulder, and hip of the nude figure. The hair and remaining skin tones are severely abraded, especially in the face.The nude’s expression and hair arrangement are obscured. H er proper right hand, poised above the basin in a gesture suggesting pouring or ringing, is also damaged. It is no longer possi­ ble to determine whether or not she holds an object, such as a vial or sponge. Paint losses obscure the eye, profile, ear, neck­ line, and proper right forearm of the robed fig­ ure. Although her red robe is somewhat better THE FOGG’S COPY AFTER A LOST VAN EYCK

85

Fig. 3. Visible-light photograph o f Copy after Jan van Eyck, Woman at Her Toilet. Oil on oak panel, 27.5 x 16.5 cm, Fogg Art Museum, Harvard University, Cambridge, Massachusetts, 1969.83. Situation on 27 May 1971, after cleaning, before inpainting. All subsequent references to Woman at Her Toilet are to the Fogg painting.

Fig. 4. Infrared photograph, 1966, o f Woman at Her Toilet.

preserved, it too can only be described as heav­ ily w orn.The two areas of white bedding sep­ arated by the bed curtain differ in paint application (both in how it was mixed and how it was brushed on), clarity, and texture; those areas to the right of the curtain are probably reworked. A large paint loss lies directly to the right of this area. The number and position of the window shutters depend on one’s inter­ pretation of the large loss at top left. Remnants of the upper right window casing above the horizontal mullion are barely detectable.

ceiling beams.The convex mirror is compara­ tively well preserved, while the basin on the chest is, apart from portions of its rim and base, mostly lost and abraded. Rem nants o f black brushstrokes are all that remain to depict the little dog. A possible carved figure and low relief on the high-backed chair are too abraded to decipher. The blue seat cushion and vessel on the foot ledge o f the chair are also severely worn. O n the verso, the green and brown mar­ bling layer has many large losses and active blind cleavage (detachment between the paint and the ground with no cracks that might allow for the introduction of an adhesive to secure the paint). The extent o f damage is so severe that the painting appears to have suffered from a combination of forces. Water damage, climate

The space behind the women, including the back wall and ceiling, is entirely abraded. Only small remnants of original paint remain to sug­ gest the initial wall color and the existence of 86

THE FOGG’S COPY AFTER A LOST VAN EYCK

Fig. 5.Visible-light photograph o f Woman at HerToilet after partial overpaint removal in 1966.

extremes, inherent defects or instabilities of the artist’s materials, or overzealous cleanings may all have contributed to its degradation.

C onservation and E xam in ation

The painting has been treated three times since the 1960s, most recently in 1996. How­ ever, the condition of the panel suggests that paint loss and subsequent restoration began long before then. Elizabeth Jones, chief conservator at the Fogg from 1952 to 1974, observed four or five layers of overpaint in certain areas.17 In 1966,Thomas Grange, conservator at the Courtauld Institute in London, studied the painting, taking an X-radiograph and an infrared photograph. He examined the paint­ ing under a stereomicroscope and described

Fig. 6.Visible-light photograph o f Woman at HerToilet prior to the 1971 treatment.

the blue as ultramarine. Grange’s report noted that much of the visible paint was “obviously modern restoration.”18 His infrared photograph (fig. 4) shows the degree to which the paint­ ing had deteriorated by the time it came into Grange’s hands. Black lines sketched into the loss at the upper left interpret the horizontal mullion as the top o f the window. They also suggest that the w indow had two shutters, rather than three. The background wall is dark and appears extensively overpainted. R ather free retouching is plainly visible in the bed cur­ tains, though the extent of retouching in the draperies and skin tones is not detectable in the infrared photograph. Later in his report, Grange stated that “in order to investigate further, it was decided to remove some o f the grosser retouching.” A black-and-white photograph (fig. 5) presumably shows the state of the paint­ ing after this partial removal of the overpaint. THE FOGG’S COPY AFTER A LOST VAN EYCK

87

By the time the painting reached the Fogg, however, the most prominent losses had been inpainted once again (fig. 6).This treatment must have taken place in England prior to the picture s being exported to the United States. The goal of this restoration was most likely to unify the image and minimize the appearance of damage. Another treatment ensued in the early 1970s, after the painting came to the Fogg.19 X-radiographs and infrared photographs, as well as black-and-white images and color slides before, during, and after treatment, documented this new work. Using a scalpel and working under the microscope, Jones removed the earlier over­ paint, including retouchings covering the back wall and ceiling o f the painting. The duringtreatm ent “stripped-state” black-and-white photograph (fig. 3) is the best document of the original paint layer’s state o f preservation and shows how little original paint is left in the dark back wall and ceiling beams.The window shut­ ters, water basin, and large portions o f the chest are missing. In the 1960s and early 1970s— w hen the Woman at Her Toilet was first being conserved at the Fogg— conservators, art historians, and related professionals once again vigorously debated the m anner o f presentation and degree o f inpainting appropriate for heavily damaged paintings. Contemporary discussions are reflected in the proceedings o f a 1961 Princeton symposium entitled “The Aesthet­ ic and Historical Aspects o f the Presentation o f Damaged Pictures.”20 Discussants at the symposium proposed a great range of suitable levels o f inpainting. Philip Hendy, then direc­ tor o f the National Gallery, London, thought it politically unwise not to restore losses and “foolhardy” to “strip” paintings in a collec­ tion.21 Richard Offner, professor at the Insti­ tute o f Fine Arts, New York University, argued for the opposite extreme, stating that any “restoration that introduces paint or shape within its boundaries, even if the restoration be limited to the missing portions alone, must prove intolerable.”22 George Stout, the Fogg’s first conservator and conservation scientist but at the time director o f the Isabella Stewart Gardner M useum in Boston, was one o f the moderate voices at the symposium. He sugTHE FOGG’S COPY AFTER A FOST VAN EYCK

Fig. 7. Visible-light photograph o f Woman at Her Toilet prior to the 1995—96 treatment.

gested that, faced w ith a specific problem, all involved parties should agree on the logical course to be taken.23 In the 1970s treatment, Fogg conservators and curators decided to minimally reconstruct the Woman at Her Toilet, toning in only the brilliant white gessoed losses, without attempt­ ing to disguise the extent of damage (fig. 7).24 Although intended to present the condition o f the painting more truly, this decision left the painting open to possible misinterpreta­ tion. For example, the form of the shutters was neither outlined nor suggested and so could be read as a solid mass and perhaps interpret­ ed as a piece o f furniture, such as a cupboard, viewed from the side. Conversely, the table top did not read as a solid form, and the water basin looked transparent and almost like glass. The unintegrated losses significantly altered

the space in which the figures stood.This was especially noticeable in the background, which at some stage had been cleaned down to the cream -colored ground and was allowed to remain as such in the 1970s treatment. W ith the dark paint missing from the background, the picture lost its sense o f depth, and the two women appeared to float in an abstract space rather than be anchored in a carefully struc­ tured room. In this state, the painting hardly resembled the image in the Van Haecht painting, which was thought to have been copied directly from Van Eyck’s original.The unintegrated Woman at Her Toilet looked like a conservation treat­ ment halted in midstream. It led to confusion, even for the experts. In a 1976 article for the Fogg’s annual report, photo captions were inadvertently reversed, changing the “before­ treatm ent” photograph into an “aftertreatm ent” photo and vice versa.25 It was probably a typesetter’s error, but it is telling that no one noticed the mistake. For the next twenty-five years, the painting spent most of its time in storage. The 1996 reinstallation of the Harvard U ni­ versity Art Museum’s collection of early Ital­ ian and N orthern paintings occasioned the panel’s most recent treatment.26 After much discussion, curators and conservators decided to reconstruct the missing background to improve the panel’s readability and make the painting more exhibitable.27 Recognizing the poor condition of the painting and desiring to keep its treatment to a minimum, they chose to remove varnish and retouchings applied in the early 1970s only where absolutely neces­ sary (i.e., where new paint and varnish over­ lapped what appeared to be original paint), and otherwise inpaint on top of old repairs. Areas of blind tenting paint were set down and con­ solidated using heat alone. Some areas of abra­ sion, such as in the foreground floor and in the chair, were mpainted to integrate the compo­ sition, but no attempt was made to disguise the very abraded state of the painting, and the inpainting can easily be distinguished with the naked eye from the original paint. Should fur­ ther conservation be desired in the future, all of the varnishes and paint used in this treat­ ment (as well as in the 1970s treatment) can

easily be removed with solvents that will not affect the remaining original paint. The detail from Van H aecht’s painting (plate 8a) provided the visual guide necessary to weave together remnants o f the missing details. Using this image, nearly indecipherable vestiges of the dog, the blue pillow, the flask on the chair, and the clothed woman’s chain and carafe in the Fogg painting were reconstruct­ ed. Shadows around and on top of the water basin were replaced, making sense of this for­ merly illegible detail, and the horizontal win­ dow mullion was reinstated. The most speculative inpainting— the dark background wall, the orientation o f the ceiling beams, the positioning o f the window shutters, and the neckline o f the red dress— relied completely on Van Haecht’s version of the composition. The half-open position of the upper shutter, previously completely missing in the Fogg painting, was closely copied from the Van Haecht image.This reconstruction of the shut­ ters divides them into three approximately equal parts, similar to the shutters in the Portrait of Giovanni (?) Arnolfini and His Wife. The earlier painting style of the figures in the Fogg work bears little resemblance to the seventeenthcentury figure style in the Van Haecht version, and so the heavily damaged areas of the faces and the paint losses in other parts of the figures were toned in w ithout reference to the Van Haecht painting.

A dd ition al T echnical Studies

The 1995—96 conservation treatment pro­ vided an opportunity to reexamine the paint­ ing and to carry out further technical analyses. The infrared photographs taken at the Courtauld in 1966 and at the Fogg in 1971 revealed interesting information regarding the painting’s condition and various campaigns of retouch­ ing but had not shown any sign o f under­ drawing or significant changes by the artist. In 1996, the panel was examined and document­ ed with infrared reflectography (IRR), a tech­ nology not available to the earlier examiners. Three pentim enti in the painting became slightly more visible under IR R than in visi­ ble light. These include a slight change in the dark outline o f the lower border o f the red THE FOGG’S COPY AFTER A LOST VAN EYCK

89

Fig. 8. Infrared digital photograph o f Woman at Her Toilet (IRDP:Teri Hensick, 2002).

Fig. 9. X-radiograph o f Woman at Her Toilet.

dress, a change in the outline of the convex mirror, and a change in the central shutter men­ tioned earlier. The changes in the shutter and the convex m irror are also visible in the cleaned-state photograph of the painting (fig. 3). Neither IR R nor infrared digital photography (fig. 8)28 revealed any evidence of an under­ drawing.

panel in order to carry out dendrochronological dating (plate 9). Klein determined that the panel was made of oak from the Baltic/Polish region. He observed 123 growth rings, of which the youngest heartwood ring dates from 1494. Klein indicated an earliest possible felling date of 1503 with a possible creation date from 1511 upwards, a good seventy years after Van Eyck’s death.31 Thus, the painting could not possibly be a contemporary fifteenth-century copy.32

In January 1996, the painting was X-radiographed again (fig. 9).29 Losses on the back of the panel in the thick ground and the paint lay­ er reduced the legibility o f the X-radiograph, as did the two channels that held the battens removed during the 1970s treatment. The X radiograph was digitized and superimposed with images of the front and verso of the paint­ ing to study the precise locations of the losses.30 In May 1996, Peter Klein, of the University of Hamburg, measured the tree rings on the 90

THE FOGG’S COPY AFTER A LOST VAN EYCK

The Fogg painting was also examined to determine whether paper or vellum was pres­ ent between the ground and the wooden sup­ port. In two other Eyckian paintings, such interlayers have been found.33The Fogg paint­ ing’s uneven, slightly cupped surface and many paint losses suggested that an intermediate lay­ er might have been present in the Woman at Her Toilet as well. No such layer was found, how­ ever. Analysis with Fourier transform-infrared

No.

1

Color

yellow

Sample Area

low er edge

Location

Chemistry

Polarizing

(cm)

(m icroprobe)

M icroscopy

1 1 .0 x 0 .6

Pb, Ca, Si, Mg,

w o o d section w ith

K, Al

lead w h ite , yellow

lead w h ite, calcite,

ochre

yellow ochre

foreg rou nd In brow n area 2

yellow

excavated pow der

1 1 .0 x 0 .6

Ca, Pb, Si, (Fe)

fro m no. 1 3

black/w hlte

dark green marble

n o t specified

paint on verso 4

w h ite

w h ite o f headdress

Ca, Si, Fe, Al,

calcite, lead w h ite,

calcite, lead w h ite,

ye llo w ochre

yellow ochre

calcite, carbon black

calcite, carbon black

1 2 .3 x 2 2 .7

Pb, Si, AI, (Zn),

lead w h ite

lead w h ite (zinc,

(TO,

tita n iu m , and

(Ca), (Cl) yellow /black

excavated pow der

w o o d structure w ith

K, (Pb)

(Fe), (Cr),

5

Interpretation

1 2 .3 x 2 2 .7

from no. 4

chrom ium oxide?)

Pb, Ca, (K),

lead w h ite , calcite,

lead w hite/carbon

(Ca), (P)

yellow ochre

black— probable bone black, calcite, yellow ochre

6

blue

bed curtains

5.3 x 8.0

SI, Al, Ca, (Na),

ultram arine blue

ultram arine blue

(Fe), (S), (Cl) 7

blue area

excavated pow der

5.3 x 8.0

Ca, (Pb), (Si)

calcite

calcite

1 0 .8 x 4 .6

Ca, (Pb), (Si)

calcite, carbon black

calcite/carbon

from no. 6 8

yellow

hem o f red dress

9

mustard

lo w er edge

yellow

beyond barb

black 11.1 x 0.3

Ca, Si, (Pb),

(Fe), (K)

calcite

coarse-grained calcite, yellow ochre, lead w h ite

Table 1.Analysis o f dispersed paint samples. Sample locations are measured from the lower left corner (h x w). Major elements are in bold; trace elements are in parentheses.

microscopy (FT-IR) did not reveal a match for protein (vellum), and microscopic examination of cross sections did not reveal any fibers oth­ er than those associated with the cellular struc­ ture of wood.

E xam in ation o f P igm en ts

A small number of paint samples and cross sections were analyzed by Eugene Farrell, senior conservation scientist at the Straus Center for Conservation. Dispersed pigment samples were analyzed using FT-IR and energy-dispersive spectroscopy with electron probe microanaly­ sis (EDS-EPMA) and examined with a stere­ omicroscope in transmitted and reflected visible light. The results are summarized in table 1.

Cross sections were also analyzed using EDSEPMA, and the results are summarized in tables 2a and 2b. The white ground on the front and back of the panel was found to consist of chalk. Fos­ silized marine microorganisms were visible in cross sections taken from the front (plates 10a and 10b) and back o f the panel. These indi­ cate the use o f a naturally formed chalk rather than a precipitated chalk. Analysis o f the dis­ persed samples and cross sections determined the presence of the following pigments in the original paint: lead white, calcite (an impurity com m on in hand-ground minerals), yellow ochre, lead-tin yellow (Type I), red ochre, ver­ milion, ultramarine blue, and carbon black. These materials are consistent w ith early THE FOGG’S COPY AFTER A LOST VAN EYCK

91

Layer 1 Brown

Chem istry

M icroscopy

Interpretation

Pb, Fe, Al, (Si),

Large carbon black grains in m atrix

Carbon black mixed w ith

(Ca), (K);

o f lead w h ite and yellow ochre

ye llo w ochre, lead w h ite , lead-tin

Pb, Sn, Fe, Si

2 Cream

Pb, Ca, Fe

yellow, and lead w h ite M ostly w h ite particles w ith

Lead w h ite , calcite, and ochre

some yellow and brow n grains 3 Yellow

Sn (Pb);

Yellow and ye llo w -b ro w n particles

Lead-tin yellow

Ca;

Fossiliferous chalk w ith occasional

Chalk (C a C 03) w ith fossils

Ca, P

darker spherical particles w ith P

Pb, Sn

4 W hite ground

Table 2a. Cross section analysis, sample no. 1 (plate 10a), from the lower edge in the foreground (11 cm x 0.6 cm from lower left corner).T he sample consists o f three overlapping pigm ent layers and a ground. M ajor ele­ m ents are in bold; trace elements are in parentheses.The results o f m ultiple measurements w ithin one layer are listed on different lines, separated by a semicolon.

Layer

Chem istry

1 Black

Ca, P, (Si), (Fe)

Microscopy

Interpretation

Black particles in a th in layer

Bone black w ith traces o f ochre

scattered on the surface 2 Red

3 Yellow

H g , S;

Large grains o f verm ilion w ith

Fe, Si, Ca, Pb, (Al)

fin e r grains o f yellow and red

red ochre, some bone black, and traces

ochre w ith quartz and bone black

o f yellow ochre and calcite

Yellow grains (lead-tin yellow )

Lead-tin yellow w ith lead w h ite

Pb, Sn

Red layer o f mixed verm ilion and

and w h ite 4 W hite

Ca

Fossiliferous calcite (chalk) ground

Calcite (chalk) ground

ground

Table 2b. Cross section, sample no. 10 (plate 10b), from the chair in the lower left (0.7 cm x 5.6 cm from low­ er left corner). T h e sample consists o f three pigm ent layers and a ground. M ajor elements are in bold; trace elem ents are in parentheses. T h e results o f m ultiple m easurem ents w ithin one layer are listed on different lines, separated by a semicolon.

Netherlandish painting techniques. M odern pigments, indicated by traces o f zinc, titani­ um, and chromium, were identified in remnants of retouching present on some of the samples. Under the stereomicroscope, a yellow layer appeared to be present underneath the upper paint layers in some locations. Although no medium analysis was undertaken, the paint lay­ er has the characteristics of oil paint, with an irregular crack pattern. Cross sections con­ firmed the presence o f a yellow layer beneath the upper paint layers in samples taken from the umber floor tiles along the lower edge and 92

THE FOGG’S COPY AFTER A LOST VAN EYCK

the folding chair at the left (plates 10a and 10b). Lead-tin yellow (Type I) (Pb9S n 0 4) was iden­ tified in this layer. This identification in the cross sections is especially helpful because thus far, lead-tin yellow has been identified only on paintings dating between 1300 and 1750.34

C on clu sion

Other copies or versions of this composition may have existed and served as models, and it is certainly possible that the Fogg painting and Van Haecht detail were not copied from Van

Eyck’s original or one from the other.35 Details such as the dog and the pattens, as well as the overall composition, however, attest to their close relationship. A better understanding of copying practices from the sixteenth century onward might help to further clarify their connection. Technical exam ination has provided the most concrete information thus far for dating the panel. Peter Klein’s dendrochronological work places the panel after 1511. Identifica­ tion o f lead-tin yellow suggests an end date of

c. 1750. By contrast, technical examination was o f limited help in the conservation treat­ ment of this very damaged work. It could not provide evidence to help reconstruct areas of loss and abrasion. While emphasis was placed on the strong connection between the Fogg’s Woman at Her Toilet and Van Haecht’s version of the composition, final inpainting decisions were the result o f discussions between con­ servators and curators and, o f necessity, sub­ jective. Future discoveries, changing tastes, or advances in technology are likely to demand that the panel be treated again.

THE FOGG’S COPY AFTER A LOST VAN EYCK

93

NOTES

1. For further information on the early history of the Straus Center for Conservation, see R on Spronk’s article in this pub­ lication.

drawing for the window shutters in the Arnolfini double por­ trait shows that Van Eyck changed their configuration, raising the center shutter considerably in the final paint stages. An artist’s change at the lower edge of the central shutter of the 2. For further discussion of Van Haecht’s The Cabinet of Fogg work, which has become more visible with repeated Cornells van der Gheest, see Baudouin 1969 and Filipczak 1987, treatments over time, suggests a similar alteration. See Billinge esp. 47-71. and Campbell 1995, esp. 49, fig. 1. See also Campbell 1998, 3. The digitally corrected image was first published in Spronk 177, fig. 1. 1996a, 13, fig. 7b. 15. Held 1957,83. 4. Friedländer 1924 (1967), 114 (68).

5. In Michael Baxandall’s translation: “There are also fine paintings of his in the possession of that distinguished man, Ottaviano della Carda: women of uncommon beauty emerg­ ing from the bath, the more intimate parts of the body being with excellent modesty veiled in fine linen, and of one of them he has shown only the face and breast but has then represent­ ed the hind parts of her body in a mirror painted on the wall opposite, so that you may see her back as well as her breast. In the same picture there is a lantern in the bath chamber, just like one lit, and an old woman seemingly sweating, a puppy lapping up water, and also horses, minute figures of men, moun­ tains, groves, hamlets and castles carried out with such skill you would believe one was fifty miles distant from another. But almost nothing is more wonderful in this work than the mir­ ror painted in the picture, in which you see whatever is rep­ resented as in a real mirror. He is said to have done many other works, but of these I have been able to obtain no complete knowledge.” See Baxandall 1964,102—3. Held noted that Fazio does not specifically describe the Woman at Her Toilet but indi­ cated its general classification with a lost category of paintings by Van Eyck; see Held 1957,74. Held also mentioned a small auction catalogue from 13 August 1668 that provides further support for the painting being by Van Eyck. The painting, then in Pieter Stievens’s collection, was described thus: “De Jean Van Eyck. num. 3. Le Bain très renomé en lequel Van Eyck a dépeint le Pourtraict de sa femme nue et vêtue.” Ibid., 84.

16. Campbell 1998,174-211, esp. 201 and n. 296. 17. Undated letter from Agnes Mongan to Thomas Grange. Curatorial files, Fogg Art Museum, Cambridge, Massachusetts. 18. University of London/Courtauld Institute ofArt 1966. 19. Jones 1975. 20. Smyth et al. 1963. 21. Ibid., 140. 22. Ibid., 157. 23. Ibid., 183. 24. Jones 1975: “The minimal amount of retouching was done.” 25. Schabacker 1976, 62—63, figs. 3 and 4. 26. Investigating the Renaissance was curated by Ivan Gaskell, M argaret S. W inthrop Curator, D epartm ent of Paintings, Sculpture and D ecorative Arts, and Stephan Wolohojian, National Endowment for the Arts Intern, Fogg Art Museum. 27. Hensick 1996. Curator Ivan Gaskell, special conserva­ tion intern R on Spronk, and conservators Teri Hensick and Kate Olivier participated in the discussions of the treatment of the painting.

6. Hammer-Tugendhat 1989; Seidel 1991,38-41. 7. Dhanens 1980,206-11. 8. Schabacker 1976. 9. Ridderbos 1993, esp. 53ff. 10. Friedländer 1924,113—14.The Fogg panel is quite close to one-quarter the width of the London painting but does not correspond equally closely to one-quarter its height. 11. Held 1957,83. 12. This does not rule out the existence of a lid in the fif­ teenth century, as Held pointed out; see Held 1957, 83. It is not known whether the missing wings for the Arnolfini por­ trait were painted by Van Eyck or subsequendy added by anoth­ er artist, possibly for its first recorded owner, Don Diego de Guevara. See Campbell 1998,174. 13. Held noted that Van Haecht cannot be depended on entirely for painting pictures exacdy to scale; he tended to por­ tray small pictures as larger than their true dimensions; see Held 1957,76, n. 49. 14. Another possible corresponding detail is provided by infrared reflectograms of the Arnolfini painting. The under­

94

THE FOGG’S COPY AFTER A LOST VAN EYCK

28. The painting was examined with an Inframetrics InfraCAM, a shortwave solid state infrared video camera with a platinum silicide detector with a 256 x 256 charge-coupled device (CCD) array. A bandpass filter of width 1.5—1.8 A was used.The camera was mounted on the Straus Centers x—y car­ riage, using a Newport tilt table 37S, and an Oriel narrow car­ rier with a 24-inch precision optical rail 11641, a setup that allows for precise alignment. The camera’s analog signal was digitized using a Scion videoboard, and a Scion-modified ver­ sion of the National Institute of Health’s image software was used to capture the camera’s video signal. Infrared digital pho­ tography (IRDP) was done using a Phase One digital back designed for a Hasselblad camera. The Phase One has a silicon CCD sensitive up to 1.1 microns, with a digital resolution of 3120 x 2060 pixels. 29. A Baltospot X-ray apparatus was used. X-radiographs were shot at KV 50, MA 5, for 60 seconds. 30. See further the article by Henry Lie in this book. In 1995—96, the Straus Center began using Adobe Photoshop to superimpose technical images and view them in layers.These images are best used on a computer, where it is possible to magnify small details for comparison between X-rays, IR R , visible light, etc.

31. Transcription of a report from 28 May 1996 by Peter Klein, University of Hamburg. “The oak panel (27.5 x 16.5 cm) contains 123 growth rings. The wood concerned origi­ nates from the Baltic/Polish region. Using this master chronol­ ogy, the rings could be dated between the years 1494 and 1372. The youngest heartwood ring was formed out in the year 1494. ... With a minimum of 2 years for seasoning, an earliest creation of the painting is possible from 1505 upwards. Under the assumption of a median of 15 sapwood rings and a mini­ mum of 2 years for seasoning, a creation is plausible from 1511 upwards.” Klein 1996b. 32. Since the panel consists of a single small piece of oak, only 16.5 cm wide, it could have come from a tree felled later than the sixteenth century, with the later growth rings planed away. Dendrochronological evidence cannot definitively deter­ mine an end date for the panel’s creation.

33. Heller and Stodulski 1998; Butler 1997. Attributed to Jan van Eyck, Saint Jerome in His Study, c. 1435. Oil on paper on oak panel, 20.6 x 13.3 cm. Detroit Institute of Arts, 25.4. Jan van Eyck, Saint Francis of Assisi Receiving the Stigmata, 1430—32. Oil on vellum mounted on panel, 12.4 x 14.6 cm. Philadelpia Museum o f Art, John G. Johnson Collection, 314. 34. Lead-tin yellow Type I is more common, but Type II (which, according to Hermann Kühn, may contain “free tin oxide and additional silicon”) is generally found on earlier paintings. See Jacobi 1941 and Kühn 1993, 84-87. 35. Held notes that the painting in Van der Gheest’s collec­ tion after which the Van Haecht work was painted could itself have been a copy of a lost Van Eyck; see Held 1957, 76.

THE FOGG’S COPY AFTER A LOST VAN EYCK

95

T h e F ogg Art M u seu m ’s Virgin and Child fro m the W orkshop o f D irk Bouts: Findings from T echnical E xam inations a n d R ecen t C onservation T reatm ent Gianfranco Pocobene and R o n Spronk Harvard University A r t M useums Introduction

One of the highlights in the collection of ear­ ly Netherlandish paintings at the Fogg Art Muse­ um is the exquisitely painted Virgin and Child (plate 11) from the workshop of Dirk Bouts. In 1911 the painting was listed in the Stroganoff collection in Rome, but nothing is known about the work’s provenance prior to that date. By the 1920s, it appeared on the New York art market, and in 1929 it was acquired by Jesse Isidor Straus, Idarvard class of 1893. It was given to the Fogg in 1959 by his widow in memory of her husband.1 In 1996, in preparation for its inclusion in the Fogg Art Museum’s exhibition Investigating the Renaissance, it was decided to remove the dis­ colored restorations and yellowed varnish layers from the painting; prior to this treatment the pan­ el was subjected to a series of technical exami­ nations.2The Virgin and Child had been studied in the past, but its reexamination and subsequent treatment revealed several important features that provided new insights on its painting technique, allowing for fresh observations on the panel’s original function and supporting the attribution to the workshop of Dirk Bouts. Many of these observations have been published by R on Spronk elsewhere3 but are presented here with unpub­ lished findings from the conservation treatment and instrumental analyses. In addition, issues and considerations regarding the stability, appearance, and appropriateness of the varnish coating that was applied to the work are reported.

Technical E xam in ation s and A rt H istorical Im plications

The Virgin and Child was studied with X radiography and infrared reflectography (IRR);

an infrared photograph was already available. The paint surface was examined with stereo­ microscopy. Paint and medium samples were analyzed with Fourier transform-infrared microscopy (FT-IR) and energy-dispersive spectroscopy with electron probe microanaly­ sis (EDS-EPMA). Paint cross sections were studied under the microscope in reflected and polarized light.4 In its present state, dendrochronological dat­ ing of the Virgin and Child is not possible since the panel is mounted on an auxiliary support that precludes access to its original edges (see below).The original support was thinned to a thickness of about 2 mm, an amount insuffi­ cient to permit study o f the pattern o f growth rings through X-radiography. Removal o f the auxiliary support was not considered. The IFkR of the Fogg Virgin and Child reveals little underdrawing related to the painted image, except for a few contour lines. The thumb and index finger of the Virgin’s proper left hand were underdrawn in a slightly high­ er position (fig. I).5 As early as 1961, however, infrared photography revealed the presence of an underdrawing o f a standing figure com ­ pletely unrelated to the image of the painting.6 Figure 1 shows the outlines o f the head, shoul­ ders, torso, legs, and feet of a female nude.This underdrawing is also mostly contour in type, but a small section o f fine parallel hatching can be observed in the lower proper left leg o f the nude.This initial composition was abandoned: The figure was never painted on this panel, which was used instead as a support for the Vir­ gin and Child. Schabacker7 demonstrated that this underdrawing o f a standing female nude is strikingly similar to the figure in another work in the Fogg, the Woman at Her Toilet, a copy after THE FOGG ART MUSEUM’S VIRGIN AND CHILD

97

Fig. 1. Workshop o f D irk Bouts, Virgin and Child. Oil (and tempera?) on w ood panel, 30.5 x 21.6 cm. Fogg Art Museum, Harvard University, Cambridge, Massa­ chusetts, 1959.186. Digital infrared reflectogram assembly. (IR R and digital composite: R o n Spronk) Fig. 2. Copy after Jan van Eyck, Woman at Her Toilet. Oil on oak panel, 27.5 x 16.5 cm. Fogg Art Museum, Harvard University, Cambridge, Massachusetts, 1969.83.

a lost composition by Jan van Eyck (fig. 2; see also plate 6, which accompanies the article by Teri Hensick in this volume). Except for a slight difference in the angle o f the heads, the out­ lines o f the two figures are extremely close, especially in the position o f the arms, hands, legs, and feet. These two otherwise unrelated works are currently displayed in the same case in Investigating the Renaissance. Until recently, most of the art historical lit­ erature on the Fogg’s Virgin and Child empha­ sized the panel’s close relationship w ith the Virgin and Child in the Städelsches Kunstinsti­ tut in Frankfurt am Main, a composition of nearly identical size in which the orientation of the figures is reversed (fig. 3).8 The Frank­ furt and Cambridge panels measure 31.3 x 22.2 and 30.5 x 21.6 cm, respectively; the painted surfaces measure 29.9 x 20.8 and 28.5 x 19.6 98

THE FOGG ART MUSEUM’S VIRGIN AND CHILD

cm.The works depict the same subject matter in similar compositional schemes; however, the two compositions are reversed and rendered in different color schemes.The FoggVirgin is also depicted more frontally than the Frankfurt one. In addition, the compositions differ in two oth­ er details: In the Fogg version, theVirgin’s prop­ er right index finger is placed over the child’s arm,9 and the child’s left index finger points to the right. In the Stadel panel, theVirgin’s left index finger is depicted underneath the child’s arm, and the child’s right hand appears with fingers curled. Scholars such as Max J. Friedländer,Wolfgang Schöne, and Erwin Panofsky have all stressed the close relationships o f aspects o f the two compositions and attributed the two panels to the same hand or workshop. Friedländer thought that both the Cambridge and the

Fig. 3. Dirk Bouts and Bouts Workshop, Virgin and Child. Oak panel, 31.3 x 22.2 cm. Städelsches Kunstinstitut, Frankfurt am Main, 1217.

Frankfurt panels were painted by Dirk Bouts himself.10 Schöne attributed both works to the Master of the Munich Arrest of Christ, identi­ fying the Fogg panel as the more mature work, painted under the influence of Flugo van der Goes.11 Panofsky also emphasized the similar­ ities between the compositions and placed both panels in the workshop o f Dirk Bouts.12 In 1993, however, Jochen Sander broke with this tradition by attributing the Frankfurt Vir­ gin and Child to “Dirk Bouts and Bouts work­ shop” and the Fogg panel to the “circle o f Dirk Bouts.” 13 He published an observation about a small but important compositional change between the underdrawing and the paint sur­ face o f the Stadel panel. Although the Virgin’s left index finger is positioned underneath the child’s arm in the visible painting, IR R revealed that in the underdrawing it was placed on top of the arm (fig. 4).14 This observation under­ lines the close relationship between the com­ positions: The underdrawing position o f the

Fig. 4. Dirk Bouts and Bouts Workshop, Virgin and Child, Städelsches Kunstinstitut. Infrared reflectogram assem­ bly. (IRR: Städelsches Kunstinstitut, Frankfurt am Main)

finger o f the Städel panel reflects its painted counterpart in the Fogg panel. Sander suggested that both works derived from an original com­ position, now lost, by Dirk Bouts.15 In 1996 R o n Spronk proposed that the two works were related even more closely, both in composition and technique. Comparison of X radiographs of the Fogg and Städel panels (figs. 5 and 6) revealed a striking similarity in the outlines and measurements of the figures of the Christ child in both works. Spronk proposed that the same pattern drawings or cartoons appeared to have been used for these details, which further strengthens the close relation­ ship between the two versions and suggests pro­ duction in the same workshop.16 Such pattern drawings could easily have been flipped over to produce reverse images. Instead o f detailing elaborate compositions, pattern drawings often depicted only partial figures, allowing them to be used in different combinations.17 Through a close comparison of the paint surface and the THE FOGG ART MUSEUM’S VIRGIN AND CHILD

99

Fig. 5. Workshop o f Dirk Bouts, Virgin and Child, Fogg Art Museum. X-radiograph.The lead putty fills are reg­ istered as light (X-ray opaque) horizontal bands at the top and bottom o f the panel.

IR R s o f the Fogg painting, Spronk also ob­ served that the raised index finger of the child’s proper left hand was underdrawn in a different, curled position, identical to that of the child’s hand in the Frankfurt painting (fig. 7a).18 The X-radiograph o f this detail (fig. 7b) shows the index finger as darker (more X-ray transparent) than the adjacent blue robe, which was probably underpainted with a layer of azurite and lead white. The index finger, however, is also lighter (more X-ray opaque) than the rest o f the hand, indicating that in the initial paint stage the hand might have been blocked in from the background with all fingers curled, as in the underdrawing. The outlines o f the hand and index finger were both incised and are revealed as thin, dark lines in the X-radiograph. The incised top contour of the hand follows the individual knuckles, demarcating a closed fist. Early in the painting process, but after the application of the initial paint layer, the painter evidently decided not to follow the 100

THE FOGG ART MUSEUM’S VIRGIN AND CHILD

Fig. 6. Dirk Bouts and Bouts Workshop, Virgin and Child, Städelsches Kunstinstitut. X-radiograph.

initial design but instead to depict the index finger as pointing. The raised position o f Christ’s index finger in the Cambridge panel has iconographie implications and provides information on its original function. According to Colin Eisler, Christ is not only gazing out at the viewers but also blessing them with his raised finger.19 Julius Held objected to this reasoning, since the gesture is made w ith the left hand: He asserted that the panel was more likely origi­ nally the left wing o f a diptych, in which the Christ child pointed toward a donor depicted on the now-missing right panel.20 The donor would in turn have been directing his or her prayers to the Christ child through the inter­ mediary figure o f the Virgin, creating an intri­ cate pattern of veneration and communication between the three figures and the beholder. According to Spronk, Held’s reconstruction is not only plausible but also helps to clarify the complex relationship between the Frankfurt

Fig. 7. Workshop o f Dirk Bouts, Virgin and Child, Fogg Art Museum, (a) Digital infrared reflectogram assembly, detail o f fig. 1. (b) X-radiograph o f the hand o f the Christ child. (IR R composite: R on Spronk).

Virgin and Child and the Fogg’s painting. Spronk postulated that the Städel’s version was conceived as an autonom ous composition, which was then adapted in the workshop for use in a diptych with a donor panel. In devo­ tional diptychs, theVirgin and child are tradi­ tionally depicted on the left wing, to the donor’s proper right. Had the version in the Stadel painting been part o f a diptych, the Christ child would have had his back turned to the donor. In order to function properly in a diptych, the composition had to be reversed.21 The X-radiographs of the paintings (figs. 5 and 6) revealed similar painting techniques and styles of under mo deling, further strengthening the close relationship between the two paint­ ings and supporting the assumption that they were produced in the same workshop. In both X-radiographs, the blue sections of theVirgin’s robe appear light, or X-ray opaque, suggesting that a blue pigment (which was identified as azurite in the Fogg panel; see below) was paint­ ed on top of an underlayer o f blue and lead white. Moreover, both X-radiographs reveal fine incisions around the main forms, seen, for example, along the contour demarcating the Christ child and theVirgin, which may have resulted from the transfer of the composition in the underdrawing stage. In both paintings, local applications o f lead white were used for the undermodeling of the

V irgin’s face and breast in strikingly similar fashion. Both faces are modeled in a compa­ rable method, with small, round areas of dense pigment high on the forehead, and horizon­ tal shapes on the proper right eyebrow, betw een the eyes and the nose, and on the ridge o f the nose. Both mouths are delicate­ ly modeled with small concentrations o f lead white on the upper lip and on the lower parts of the corners o f the mouth. W hen these X radiographs are compared to those o f other versions of the Virgin and Child from the Bouts group,22 it is clear that the Fogg and Stadel paintings were executed in a highly similar technique. Given this observation and the ear­ lier discussion o f the pattern drawings, it seems plausible that both paintings were produced in the same workshop.

Structure, C ondition, and Materials o f the Painting

The Fogg Virgin and Child was painted on a wood panel constructed from a single board with the grain running vertically. The support was drastically altered in a structural treatment, probably carried out early in this century, that involved thinning, flattening, and cradling.23 The original w ood panel was reduced to a thickness of only 2 mm and glued to another panel, 4 mm thick, with an adhesive o f unde­ termined composition.24The auxiliary support panel is a single oak board, approximately 1 cm THE FOGG ART MUSEUM’S VIRGIN AND CHILD

101

edges o f the panel, the ground layer is stable and well adhered to the wood support. Except for the darkening of the blue robe of theVirgin, the paint surface is well preserved. Generally, the paint layers are thinly painted, with minor buildup visible in the skin tones, white drapery, and the V irgin’s blue mantle. Eight samples were taken from the paint sur­ face and analyzed to determine the pigments and medium.26The analysis identified pigments typical of those used in Flemish painting in the late fifteenth century. Lead white was found in the white drapery, and lead white and a red lake pigment are present in the skin tones.The dark brown background contains ochre and car­ bon black.

Fig. 8. Workshop o f Dirk Bouts, Virgin and Child, Fogg Art Museum. Reverse.

longer and 1 cm wider than the original. To adjust to this increased size, two thin oak strips were glued to the panel, on the left and the right edges. Curiously, the top and bottom edges were not finished in the same manner. Instead, the edges were filled with gray putty (see fig. 5 and pi. 14) and then painted in oil to simulate a wood grain pattern similar to the oak strips on the left and right. A heavy mahogany cradle was then applied to the back to keep the panel flat (fig. 8). To date, the panel has remained flat overall. The thinning and flattening of the panel result­ ed in some long vertical splits, including sev­ eral very fine ones that were possibly caused by the transfer process and the restrictive cradle. All splits and cracks remain stable at this time. M inor undulations are also visible on the sur­ face; these might have occurred as a result of the uneven thinning of the panel. The smooth ground layer of the painting is composed of chalk (calcium carbonate) bound in animal glue.25 Except for small losses along the m inor cracks in the painted surface and 102

THE FOGG ART MUSEUM'S VIRGIN AND CHILD

The underlayer o f the Virgin’s blue mantle in the Fogg painting is composed of azurite and lead white, with subsequent applications of pure azurite glazes, creating an intense, deep blue effect. Artists o f the time were aware that cer­ tain pigments such as azurite become saturat­ ed and darkened w hen suspended in oil. Analysis o f the paint revealed that it is com­ posed o f pigments suspended in a drying oil, but protein is also present in the sample from the blue robe. Since both oil and protein were detected, egg or glue may have been used to bind the azurite glazes to achieve a more bril­ liant and intense effect. The now-darkened appearance of the blue can most likely be attrib­ uted to the application o f oleo-resin varnish coatings in previous restoration treatments. It is quite possible that, unlike the rest of the paint­ ing, the blue robe was left unvarnished by the artist in order to avoid darkening. To our knowl­ edge, the pigment used for the Frankfurt Vir­ gin and Child has never been analyzed. In the London Virgin and Child, theVirgin’s blue robe was painted with ultramarine over an earlier layer o f azurite. The m edium there was lin­ seed oil, but egg was found in the lower layer o f azurite.27

C onservation T reatm ent

Until the recent cleaning, only minor treat­ ments had been carried out on the painting while in the Fogg collection. These included light surface cleaning, consolidation o f tiny

areas o f flaking paint, and an application of a layer of dammar varnish in 1989 to revive the old and degraded natural resin surface coat­ ing. By 1996, the yellowed and oxidized var­ nish coatings had darkened to such a degree that the tonality o f the painting had become unacceptably altered (plate 12). Examination o f the surface with ultraviolet light revealed a highly fluorescent surface coating, w hich confirmed that the varnish layer had degrad­ ed significantly. Examination with ultraviolet light also revealed numerous areas of old inpainting and retouching, many of which appeared to cover original paint, especially along theVirgin’s face and hands and the white drapery. Some of these retouches were not intended as inpainting but were instead applied in areas where the under­ drawing for the standing nude had become vis­ ible to the naked eye.28 It was decided to remove the old varnish lay­ ers and the scattered retouchings that covered abrasions along the top and bottom edges and the proper left hand of the Virgin. Solubility tests were performed using various solvent mix­ tures, and it was determined that the varnish layers could be safely removed from the paint­ ing. The degraded varnish layers and old retouchings were removed with an isopropanol and acetone mixture on cotton swabs (plate 13). As a result, the paint surface regained its cooler tonality, and contrast between the lighter and darker areas was reestablished. Although the blue robe o f the Virgin remains irreversibly darkened, it once again stands out from the brown background. The removal of the varnish layers, overfills, and overpaint revealed that the paint surface is generally in good condition and that the extent o f damage is generally minimal (fig. 9). An exception is the top edge of the dark brown background, which is abraded.This was not vis­ ible under examination with ultraviolet light because of the high fluorescence of the degrad­ ed varnish.The removal of subsequent additions also exposed a continuous gray fill extending around the four edges of the panel (plate 14). The fill had been applied to the edges to lev­ el the transition between the painted surface

and the auxiliary support at the top and bot­ tom edges and the wood strips added at the left and right. Examination of the edges under the microscope revealed that the fill covered orig­ inal paint surfaces along all four sides (plate 14). Under magnification with a binocular micro­ scope, a scalpel was used to lift the brittle fills off the original paint surface. This process exposed the original paint layers and a barb, a raised ridge of white ground layer and paint, that had filled the inner edge o f the original frame along all four sides but that was especially evident along the left, right, and bottom edges (plate 11).This feature indicates that the sup­ port panel was outfitted with an engaged frame before the ground was applied. The fact that the barb is present on all sides o f the panel also indicates that it was never cropped. Moreover, a 2-m m border painted in vermilion was revealed just inside the barb along all four edges of the painting. The next step in the treatment of the panel was the retouching of losses and the reappli­ cation o f a varnish coating. First, a synthetic resin coating,29 chosen for its stability and reversibility, was applied to the painting with a brush to isolate the original surface prior to the restoration of the painting’s minimal abra­ sions and losses.These areas were then inpainted and glazed w ith dry pigments mixed in stable and reversible resin to prevent discol­ oration of the retouchings over time.30The pre­ cise locations o f the areas o f inpainting are revealed in a photograph under ultraviolet light, taken after the treatment (fig. 10).

C h o o sin g a N e w V arnish for th e Virgin and Child

A varnish coating protects the paint film and saturates the paint layers so that they retain depth and richness. Only in the late nineteenth century did painters who opted for particular matte surfaces begin to leave their paintings unvarnished. It is assumed that earlier oil paint­ ings were varnished by the artists. Traditional natural resin varnishes such as mastic and dammar undergo chemical degra­ dation in a relatively short period of time,31 especially w hen compared with a number of THE FOGG ART MUSEUM’S VIRGIN AND CHILD

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Fig. 9. Workshop o f Dirk Bouts, Virgin and Child, Fogg Art Museum. D uring treatment (after removal o f var­ nish, overpaint, and overfills; before inpainting).

Fig. 10. Workshop o f Dirk Bouts, Virgin and Child, Fogg Art Museum. Fluorescence under ultraviolet light (after treatment).

types o f synthetic clear coatings. The aging of natural resin varnishes, which has such neg­ ative effects as yellowing, cracking, cloudiness, and loss o f saturation and gloss, necessitates their removal more frequently than is desir­ able and often requires solvents that can be deleterious to the original paint layers. Over time, the repeated use of solvents to dissolve degraded natural resin coatings has caused considerable damage to many paintings, including the loss o f delicate glazes, abrasion o f the paint layers, and leaching or extraction of the oil medium, which makes the paint film brittle. Nevertheless, dammar varnish is still widely used because o f its initial appropriate appearance on older and weathered paintings.

resins be considered for conservation, and they were responsible for the introduction o f a number of new products to the field.32 Aging characteristics are still critical factors in the choice o f conservation materials, and the search for easily removable varnish resins that are stable over long periods o f time contin­ ues today.33

More than fifty years ago at the Fogg Art M useum, R utherford Gettens and George Stout recognized the desirability o f replacing conservation materials that age poorly with more stable and reversible alternatives. Get­ tens and Stout proposed that new synthetic 104

THE FOGG ART MUSEUM’S VIRGIN AND CHILD

In general, Old Master paintings on smooth solid supports such as wood panels require a relatively high degree of saturation. Since the synthetic resin applied to the Virgin and Child as an isolating varnish layer prior to inpaint­ ing did not adequately saturate the paint lay­ ers, an appropriate final varnish was sought. Traditional natural resin varnishes were not considered because of their poor aging quali­ ties. A number o f synthetic resins that matched the saturating properties o f natural resin var­ nishes were considered but were also thought unsuitable because of poor aging characteris­ tics such as cross-linking and yellowing.

After discussions w ith curators and other conservators, it was decided to apply a brush layer o f the synthetic resin varnish R egalrez 1094®, dissolved in mineral spirits; this mixture achieved the appropriate degree o f saturation and gloss.04 Regalrez 1094® was introduced by R ené de la R ie (National Gallery o f Art, Washington) as a reversible and stable substitute for traditional natural resin varnishes such as dammar and mastic. Accord­ ing to de la Rie, Regalrez 1094®, when sta­ bilized w ith an ultraviolet light stabilizer,30 remains unchanged under accelerated light aging for a far longer time than natural resins.36 The resin also remains soluble in lowaromatic hydrocarbons such as mineral spir­ its, thus greatly reducing the potential for the leaching of oil components from the paint film during future removal. In addition to its sta­ bility, the refractive index of Regalrez 1094® is very close to that o f the natural resin var­ nishes, thus providing a glossy and highly sat­ urated surface that befits many O ld Master paintings. The Virgin and Child was the first painting at the Fogg to receive this varnish coating, and its condition will be monitored regularly.

S u m m ary and C onclu sion s

The findings from these technical examina­ tions further support the notion that the Fogg’s Virgin and Child from the workshop o f Dirk Bouts is very closely related, in composition and in painting technique, to the version in the Städelsches Kunstinstitut in Frankfurt. The composition o f the Frankfurt panel, which probably functioned as an autonomous image for private devotion, was adapted to make the Cambridge, Massachusetts, panel suitable for the left wing of a diptych.The composition was reversed and the index finger of the Christ child panel was raised so that it pointed at a donor portrait on the (now missing) right wing. Sim­ ilarities in painting technique support the attri­ bution of both works to the same workshop. The conservation treatment of the Virgin and Child revealed a paint surface in good condition. The paint layers regained a cooler tonality, which had been obscured by a markedly yellowed var­ nish. Although the blue robe of the Virgin has irreversibly darkened, much o f the contrast between darker and lighter areas in the painting has been reestablished (plate 11). It is expected that the application of the synthetic resin var­ nish Regalrez 1094® will make renewed treat­ ments unnecessary for decades to come.

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NOTES

* We would like to express our gratitude to our colleagues at the Straus Center for Conservation and Technical Studies and the Department for Paintings, Sculpture, and Decorative Arts at the Harvard University Art Museums. We are especial­ ly indebted to Francesca Bewer, Eugene Farrell, Ivan Gaskell, Henry Lie, and Kate Olivier. 1. In the literature, the panel is sometimes referred to as the Stroganoff Madonna, after its one-time owner. For details on the painting’s provenance, see Eisler 1961, cat. no. 69, 54—57. 2. Investigating the Renaissance was curated by Ivan Gaskell, Margaret S. Winthrop Curator, Department of Paintings, Sculpture, and Decorative Arts, and Stephan Wolohojian, National Endowment for the Arts Intern, Fogg Art Museum. The con­ servation treatment was done by Gianfranco Pocobene.The tech­ nical examinations were carried out by Ron Spronk, in collab­ oration with Gianfranco Pocobene and Eugene Farrell, senior conservation scientist at the Straus Center for Conservation. 3. See Spronk 1996a; 2001. 4. All samples were taken and analyzed by Eugene Farrell. 5. Spronk 1996a. 6. Eisler 1961, cat. no. 69,54—57; and Schabacker 1976. See also the article by Teri Hensick in this publication. 7. Schabacker 1976. 8. A color plate of the Stadel Virgin and Child appears in Sander 1993, plate 2; see also Smeyers and Smeyers 1998,16. 9. This arrangement emphasized the intimacy between mother and child and may have derived from images of the Madonna Lactans, in which the nursingVirgin holds her breast between her index and middle fingers. 10. Friedländer 1924-1937 (1967-1976), vol. 3,28, no. 11. 11. Schöne 1938,167, no. 49. 12. Panofsky 1953,296, n. 3; 317, n. 3 (1971, 480-81, n. 3; 492, n. 3). 13. Sander 1993, 46—58. 14. Ibid., 52, and 66, fig. 19. 15. Sander proposed that both the Stadel and the Fogg com­ positions, along with a third version of the Virgin and Child attributed to an anonymous Master from the Upper Rhine and now in the Diözesanmuseum in Freising, Germany, all derived from a now-lost original composition by Dirk Bouts.The ver­ sion in Freising, however, does not show the arrangement with the Virgin’s fingers around the child’s arm. Ibid., 57.

21. Spronk 1996a, 42-44. 22. See, for example, Ainsworth 1993 and Bomford, Roy, and Smith 1986,53, fig. 16. 23. It has been suggested that the treatment might have been carried out by William Suhr. See a memo from Elizabeth Jones to Seymour Slive, 9 September 1970, on file at the Fogg Art Museum. 24. The fact that the X-radiograph of the panel clearly reveals the distribution of the original lead-white paint layers indi­ cates that a lead-white-based adhesive, often used in the remounting of thinned panels onto auxiliary supports, was not utilized in this instance. Had such an adhesive been used, the high density of the lead white would most probably have obscured the various paint layers in the X-radiograph. Most likely, wood glue such as animal glue, which contains no pig­ ment that blocks X-rays, was used to mount the thinned panel under pressure onto the auxiliary support. 25. Fine-grain calcite was observed under microscopic examination, and the presence o f calcium was confirmed with SEM microprobe analysis.This work was carried out by Eugene Farrell. 26. The samples were also taken by Eugene Farrell, who analyzed them using FT-IR and EDS-EPMA. 27. See Dunkerton et al. 1991,183-84, figs. 252-53; see also Campbell 1998, 56. 28. The Mater Dolorosa by Albrecht Bouts in the Fogg Art Museum (2001.171) received similar treatment. See Spronk 2001,444, figs. 8a,b and 11. 29. Acryloid B-72 is a high-molecular-weight synthetic resin (ethyl methacrylate and methyl acrylate copolymer); see R ohm and Haas 1975. It was suspended as a 15% solu­ tion in a solvent of CycloSol R53®; see Shell 1993. 30. Inpainting was carried out with pigments suspended in Acryloid B-72, 15% in CycloSol R53®; see R ohm and Haas 1975 and Shell 1993. 3 1 . de la Rie 1988. 32. For further information on Gettens and Stout, see Spronk 1996b; see also the article by Ron Spronk in this publication. 33. The reader is directed to the pioneering research of R o b ert Feller (Feller, Stolow, and Jones 1985) and more recently of René de la Rie (de la Rie 1987; 1988; 1993; and de la Rie and McGlinchey 1989; 1990).

34. Regalrez 1094® is a low-molecular-weight, hydro­ carbon resin (hydrogenated oligomer of styrene and alpha16. Spronk 1996a, 25,33,42-44; figs. 16,23,24,34-36,40,41. methyl styrene); see Hercules 1994. Varnish formula: Regalrez 1094® (Hercules) 46g/T inuvin 292® (Ciba-Geigy) 1g/ 17. See, for instance, the set of fifty-six drawings from the Kraton G l650® (Shell) 4g/mineral spirits 200HT® (Shell) Kunsthistorisches Museum, Vienna, illustrated in Dunkerton 150g.This mixture came into use by conservators at the Fogg et al. 1991,142, fig. 181, and in Harbison 1995,70, ill. 42. after Gianfranco Pocobene attended the “Varnishes: 18. This comparison was aided significantly by the overlayingAuthenticity and Permanence Symposium and Workshop.” of digitized files o f the different technical documents. For a See Carlyle and Bourdeau 1994. description of this method, see Henry Lie’s article in this volume. 35. Tinuvin 292® is a hindered amine light stabilizer (HALS). 19. Eisler 1961, cat. no. 69, 54—57. 20. Held 1962.

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3 6 . de la Rie 1993.

Interpreting A nalyses o f the P ainting M edium : A Case Study o f a P re-E yckian A ltarpiece E . Melanie Gifford, Susana Halpine,** and Suza n n e Quillen Lom ax N ational Gallery o f A rt, Washington, D .C ., and Michael R . Schilling G etty Conservation Institute

Introduction

The use of oil paint, which by the end o f the sixteenth century had become the dominant medium of easel paintings throughout Europe, changed the aesthetics o f painting. The rich colors and eloquent rendering of surface facil­ itated by the oil medium are strikingly differ­ ent from the unsaturated colors and schematic paint handling that typify egg tempera paint­ ings or manuscript illuminations. The breathtaking visual effects o f early Netherlandish artists have given rise to a long tradition attributing their achievements to unique inventions and secret formulas; in par­ ticular, the attribution of the invention of oil paint to the Van Eyck brothers was popularized by Giorgio Vasari.1 Although the romantic notion of the Van Eycks as inventors of the oil medium has long since been laid to rest, iden­ tifying the paint medium of an individual work is of more than abstract interest. In this paper, we consider a tiny altarpiece, used for personal devotion, that is now gener­ ally agreed to be a Netherlandish work from around 1400. Although the artist is not known, the altarpiece, which has long been associated with the Champmol monastery near Dijon and with the patronage of Philip the Bold, duke of Burgundy, is an outstanding example of “preEyckian” painting.2 The quadriptych has been divided, with two panels now in the collection of the Museum Mayer van den Bergh in Ant­ werp3 and two at the Walters Art Museum in Baltimore (plates 15—17; plates 15 and 16 are, respectively, the interior and the exterior of one o f the panel’s wings).4 In 1993, we had the opportunity to study the two Baltimore panels,

and in 2000 we carried out additional analysis using new methods.We reconsider this case study in the present publication. By outlining com­ plex and sometimes apparently inconsistent ana­ lytical results, we hope to illustrate an approach to interpreting technical data— and in particu­ lar the analysis of the paint medium—in the con­ text of art historical research. Specifying the painting materials, both the pig­ ments and the medium that binds them into a workable paint, and considering how artists han­ dled the materials can offer insight into artistic or aesthetic goals.We can compare these mate­ rials and procedures to those used by contem­ poraries and predecessors.The natural assumption is that a path of least resistance leads artists to continue to paint as they have been trained and as their colleagues have painted. Artists who break this pattern by adopting or introducing alterna­ tive methods and materials either reflect the prac­ ticalities of circumstances (a change of locale or economic disruptions that make the favored materials unavailable) or a new aesthetic impulse (a search for visual effects that traditional mate­ rials and techniques cannot achieve). Furthermore, analysis o f an artist’s choice of painting materials can supplement studies that focus on the appropriation of visual motifs to trace links between paintings or artists.The tan­ gible evidence of technical studies can some­ times differentiate between paintings with more superficial similarities (such as appropriated style or motifs) and those linked by direct personal contact between artists trained in differing regional traditions. This approach may prove to be particularly fruitful in a field such as the study of European paintings from the late four­ teenth and early fifteenth centuries: works exe­ THE MEDIUM OF A PRE-EYCKIAN ALTARPIECE

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cuted in the International style, such as the Antwerp-Baltimore quadriptych. Some of these works are closely allied by shared formal ele­ ments, but their authorship or even country of origin can be harder to specify.

D e v e lo p m e n t and Early U ses o f the O il M ed ium

Drying oils such as linseed and walnut oil, which dry to a hard surface, were used as paint­ ing media before the fifteenth century. How­ ever, until recently, it has been assumed that oil was used in those years primarily for decora­ tive surfaces rather than for fine art. Pure oil, without a diluent, is a viscous material that does not lend itself to the rendering o f fine detail. W riting in the twelfth century, Theophilus referred to pigment in oil used for “reddening doors” as a protective coating more than a fineart medium.5 Although he said it was possible to paint figures in oil on wood if the object could be dried in the sun between coats, he felt that the tedium of such a process recommended against it.6 Recent technical studies, however, have identified the thirteenth- and fourteenthcentury use of an oil medium in panel paintings originating in various parts o f Europe. These include altar frontals in Norway from 1250 to 13507 and in Denmark from the first half of the fourteenth century,8 English panels from the late thirteenth century,9 and a German trip­ tych o f the late fourteenth century.10 D ocu­ mentary sources also suggest that oil was frequently used as a painting medium in these years. An Icelandic manuscript dating between 1300 and 1350 described materials and tech­ niques, including oil painting, that correspond closely to Norwegian paintings of the period.11 The texts compiled in fifteenth-century Stras­ bourg and Le Begue manuscripts, both of which discuss oil painting, also suggest that this prac­ tice was already current somewhat earlier.12 Romanesque and Gothic oil paintings are generally schematic in handling, without fine detail. The achievement of the Netherlandish artists of the early fifteenth century was in refin­ ing the use of oil paint as a fine-art medium; it was this development that permitted the aston­ ishing leap in naturalism seen in the paintings of Jan van Eyck and his contemporaries. These 108

THE MEDIUM OF A PRE-EYCKIAN ALTARPIECE

artists used oil in a technique with such subtle­ ty of detail that Van Eyck created the illusion of Canon Joris van der Paele’s rich, gold-threaded brocade exclusively in paint, without gilding.13 Many theories have been advanced to explain the technical innovation of the early fifteenth century. Before technical analyses were possi­ ble, the theories were predominantly based on close observation of the paintings, on the expe­ rience of copies made after the paintings (often attempting to reproduce the effects of age), and on evidence from original sources. In his recent overview of these theories, Ashok Roy high­ lighted three frequently encountered themes: that early Netherlandish technique must have been based on emulsions o f egg and oil, that the paint handling must have depended on innumerable thin glazes, and that the use of diluents must have perm itted such a glazing technique.14 By allowing an examination of the materials of the paintings themselves, ana­ lytical investigation has considerably changed our understanding of early Netherlandish paint­ ing techniques. It now seems likely that the majority of these artists used an oil m edium.15

M ethods o f M ed ium Analysis

A few words will serve to outline the theo­ ry behind the primary methods o f medium analysis discussed here: microscopic examina­ tion o f paint cross sections using biological stains, and instrumental techniques based on chromatography16 and mass spectrometry. A third technique, microchemical analysis, which was used in some studies cited here, bases iden­ tifications on microscopical observations of the chemical reactions of paint samples with spe­ cific reagents. In all cases, the analysis is carried out on microscopically small samples of paint taken from areas where they will be unobtru­ sive, often from the edges of old damages. Biological stains are dyes that bind prefer­ entially to specific paint media. Paint cross sec­ tions are examined with a microscope before staining and then reexamined after staining for changes in color. Some stains are examined directly in visible light, others are recognized by a characteristic fluorescence when they bind to the target material. A color change in spe­

cific layers should indicate the presence of the target material in those layers; the samples must be examined critically, however, because false­ positive results are not infrequent.17

reader must recognize that occasional variations of results may be due in part to variations of analytical technique.

In the chromatographic techniques, the medium of a paint sample is put into solution, leaving behind the insoluble pigments. The sample solution containing the paint medium flows across a stationary phase, a material that selectively retards the chemical components of the mixture. The time taken by each compo­ nent to travel to the detector helps to charac­ terize the various fatty acids that make up an oil or the component amino acids o f proteins. Based on comparison with reference standards, the ratios of the fatty acids or amino acids are characteristic of specific oils or proteins. W hen chromatography in its various forms is coupled with mass spectrometry, a method o f instru­ mentation that gives clues about the structure of the various compounds, still firmer identi­ fications can be made.

T echnical Studies o f the A ntw erp—B altim ore Q uadriptych

Although many Italian easel paintings from before 1400 are available for study, few paint­ ings from outside Italy in the “pre-Eyckian” period survive. Only recently have researchers begun to apply scientific methods of analysis to the study o f the paint medium in these works, and the analytical methods available to the researchers have been varied. Publications on the few paintings analyzed to date report diverse results. Some studies analyzing preEyckian paintings primarily through micro­ chemical testing (with additional biological staining for some paint samples) have found evidence of both oil and protein media on the same painting.18 O n the other hand, analysis by gas chromatography-mass spectrometry (GC-MS) of a number o f other early works from outside Italy has identified the primary paint medium as a drying oil.19 Interpretation is as im portant in medium analysis (and other scientific investigations of works of art) as in the visual analysis of a paint­ ing’s style, composition, or iconography. Sci­ entific study should be seen not as offering categorical answers but as contributing to the entire body of evidence that can be brought to bear on the consideration of any work of art. In interpreting the publications cited above, the

Two technical studies of the panels making up the Antwerp-Baltimore altarpiece illustrate the complexity of interpreting information on paint media derived by different analytical methods. In a 1984—85 publication on the Antwerp pan­ els, Leopold Kockaert reported the analytical results for six samples taken by Jean Thissen in 1965 and two additional samples that he took himself. The samples were analyzed microsco­ pically for the identification of pigments. Micro­ chemical testing was used to characterize the paint media o f all eight samples; in addition, the two new samples were analyzed using bio­ logical stains.The analyses yielded five different results for different areas of the panels: paints that probably contain oil; paints based on egg yolk or oil; tempera; a protein medium with oil; and a protein-oil emulsion.20 A study undertaken in 1993 at the Scientific Research Department of the National Gallery o f Art in Washington, D.C., offered an oppor­ tunity to examine the two Baltimore panels using a wider range o f analytical techniques. Because of the paintings’ small size and good condition, only a very limited number of micro­ scopic cross sections were taken, and a small number o f dispersed samples were taken for pigment and medium identification. In addi­ tion to optical microscopy, which was used to identify pigments and to study the layer struc­ ture o f the paintings in cross section, X-ray analysis of samples in a scanning electron micro­ scope was used to confirm pigment identifica­ tions.21 In addition to biological staining, the facilities o f the National Gallery’s Scientific Research Department allowed for analysis of the paint media by newer instrumental meth­ ods using microscopically small samples. GCMS was used to identify oils and resins used as paint media,22 and high-sensitivity amino acid analysis (AAA) by high-pressure liquid chro­ matography (HPLC) was used to identify pro­ tein media such as egg tempera or glue distemper.2-^ In 2000, small amounts o f samTHE MEDIUM OF A PRE-EYCKIAN ALTARPIECE

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pie reserved from the earlier study were rean­ alyzed using a newly developed method of GCMS, which can characterize both oils and proteins in the same sample.24 At the same time, the amino acid data from both analyses (1993 and 2000) was studied using a computerized comparison to a database o f known proteins.25

P aintin g T echnique

The two Baltimore panels include one wing with the Annunciation (plate 15) on the interi­ or and the Baptism of Christ (plate 16) on the exterior, and an interior panel with the Cruci­ fixion (plate 17).The surfaces of the paintings show a considerable range in the handling.The decorative use of tooled gold backgrounds and of gilded brocade details is familiar from Ital­ ian painting and from N orthern manuscripts, and this extensive use of gold would be expect­ ed in a small, precious object of personal devo­ tion. Areas such as Gabriel’s wings (plate 18), in which the artist used a range o f rich glazes over the tooled gold background, contribute to the jewellike quality of the paintings. The opaque, unsaturated appearance of many areas, such as the drapery o f the kneeling Gabriel (plate 19), is also familiar from Italian pictures (although the individual paint strokes often associated with egg tempera cannot be distinguished in these details). But in an area such as C hrist’s legs visible in the stream in the Baptism, the artist seems to have used a more transparent paint than that used in Italian works with similar subjects. Here, an illusionistic use of glazing over a gilded surface creates a lively representation of flowing water (plate 20). And in areas such as theVirgin’s throne (plate 21) in the Annunciation, the wet-in-wet handling of the paint is completely unlike tempera.

A nalysis o f the P aintin g M aterials

The preparation o f the panels for painting does not seem different from many early Netherlandish paintings o f the fifteenth cen­ tury. The wood panels, which appear to be oak, were prepared with a white chalk-glue ground. In all areas tested, except gilded details, the absorbent chalk-glue ground was covered with 110

THE MEDIUM OF A PRE-EYCKIAN ALTARPIECE

a smooth, opaque, isolating layer pigmented with white lead and chalk. The results of bio­ logical staining (discussed below) suggest that this layer is particularly oil rich. The function o f such a layer must have been to seal the ground; the porous ground would have absorbed much of an oil paint’s medium, stain­ ing the white ground and weakening the paint. Indeed, in cross sections, the ground immedi­ ately below the layer is somewhat translucent where the oil-containing medium of the iso­ lating layer soaked into the ground. The addi­ tion of white lead to the isolating layer restored the reflective white of the preparatory surface. Infrared examination showed only occasional outlines o f underdrawing; since none o f the samples taken in the present study included the underdrawing, the drawing medium could not be identified, nor could it be determ ined whether the drawing was executed before or after the white isolating layer was applied. The palette and paint handling are simple. The paint was usually applied in ju st one or two layers, primarily using pure pigments to create clear colors, rather than complex mix­ tures in subtle variations o f tone. Reds and oranges were rendered with three different pig­ ments. Vermilion was used for the scarlet sky o f the Baptism. For the crimson draperies, the artist used a red lake, glazing the shadows with a lake toned with bone black26 and mixing the pigment with white lead in the highlights and mid-tones. The orange of the cloth o f honor in the Annunciation was painted in red lead. The only blue pigment identified in the draperies was ultramarine; the forms were laid out with a mixture of ultramarine and white lead, then glazed with the pure pigment. In at least one white passage, theVirgin’s throne in the Annun­ ciation, a few grains of ultramarine were mixed into the white lead to give the paint a cooler tone.The skin tones were painted directly onto the white isolating coat in a single layer. In a sample from the figure of Christ in the Cruci­ fixion, the paint is based on white lead, very slightly tinted with earth pigment. During this period, no completely satisfac­ tory green pigment was available. This artist, like many others, used different pigment mix­ tures to create several different greens. The greens o f the foliage, w hich could no t be

fully characterized, were laid down in several stages. A dark, copper-containing base coat, which is now entirely brown, may be a degrad­ ed copper-resinate green. For the foliage high­ lights on top of this layer, the artist mixed white lead and a copper green. Final details were ren­ dered in a clear green glaze, which has not dis­ colored. This layer may also be a copper resinate, but it is not clear at this time why its color should be well preserved while that of the base tone seems to have darkened. Medium analy­ sis of the individual layers would have been required to accurately identify a resin compo­ nent in these paints, but this investigation was not possible with the small samples available. Identification o f the painting medium is an issue o f critical importance in placing these works within the development of early N orth­ ern painting. The publication of the study of the Antwerp panels reported the use of a com­ plex range of media, including oil-containing paints, oil-protein emulsions, and tempera.27 The results of the present study of the Balti­ more panels suggest a simpler painting method. Some apparent inconsistencies between these studies have not been entirely resolved with current analytical technologies. Each study highlights the need for careful interpretation of complex data, including consideration of the characteristics of the analytical methods used and the paintings’ conservation histories. In 1993 it was possible to perform medium analysis on three paint samples using biologi­ cal staining and two instrumental methods, GCMS and HPLC.The analysis of the sample from the white of the Virgin’s throne in the Annun­ ciation illustrates these results: The wet-in-wet handling of this paint does not look typical of the fine, hatched strokes of egg tempera. Through the stereomicroscope, one can see the earth-colored paint o f a shadow swirled into the white paint of the throne (plate 21); a paint cross section taken from the throne showed the same w et-in-w et handling (plate 22). This painter clearly understood and exploited the properties of a creamy, slow-drying medium. Although biological staining o f paint cross sections for medium identification can be dif­ ficult to interpret, the results in this case gave some useful indication of the painting’s mate­

rials. A biological stain that was positive for pro­ teins clearly stained the ground and does not appear to have stained the isolating layer or paint layer (plate 22 before staining, plate 23 after staining).28W hen a stain for oil was used, the white isolating layer stained strongly, while the staining o f the paint layer was less obvious (plate 24 before staining, plate 25 after stain­ ing).29 Instrumental analysis clarified these results: The creamy white brush-furrowed paint of the throne is oil paint. The results o f GCMS analysis showed the presence of a drying oil medium, with fatty acid ratios typical of lin­ seed oil, as well as a trace of pine resin.30 Highsensitivity AAA by HPLC revealed no evidence o f a protein such as glue or egg as a significant component of the m e d iu m .O n ly very small amino acid peaks were observed; such peaks are consistent with the pattern observed in aged natural resin such as dammar, which has been used by restorers as a varnish since the nine­ teenth century. Interpretation of the other two samples that were analyzed in 1993 by these instrumental methods also suggested that the paint medium is primarily oil. The orange paint of the cloth o f honor was applied over gold leaf, carefully working around the tooled design. The medi­ um of this thick and rounded paint is charac­ teristic of linseed oil with a trace of pine resin. (In this sample, AAA by HPLC did record sub­ stantial amounts of amino acid in a ratio char­ acteristic of glue as well as the dammar-like pattern, but staining of the cross section revealed the glue to be restricted to the surface, most like­ ly applied during an earlier restoration.)32 Even the red sky of the Baptism, which in close micro­ scopic examination has a dry character that might have suggested the use of a glue distemper, was found to contain oil medium, again with a trace of pine resin. It was not possible to sample an ultramarine glaze for instrumental analysis, but biological staining33 of a cross section of theVirgin’s robe in the Annunciation suggests that both the glaze and the opaque blue layers were exe­ cuted in oil paint.-34 In 2000, further analysis was carried out on the very small amounts remaining from the three original samples and on one additional sample taken from a skin tone.This analysis, using a new method of GC-MS discussed above, confirmed THE MEDIUM OF A PRE-EYCKIAN ALTARPIECE

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that the primary medium in all four samples is a drying oil characteristic o f linseed oil. This method of GC-MS also can reveal the presence of proteins; again, very small amounts of amino acids were observed in all four samples. Using this technique, we cannot yet quantify the relative proportions of protein to oil, but the results again suggest that protein is at most a minor compo­ nent of the medium. The amino acid data from both the original HPLC analysis and the new GC-MS analysis were studied using a comput­ erized comparison to a database of known pro­ teins. Reexamination of the trace amino acids identified in 1993 confirmed that a material con­ sistent with aged dammar, as well as traces of glue, was present in all three samples; on the other hand, while the 2000 analysis did find amino acids, the amount of material analyzed was too small for conclusive identification of the specific protein. A rough correlation to egg, which has an amino acid profile similar to dammar, was noted. It is also possible, though every effort is made in sampling to sample a single paint layer, that the variations in analysis actually reflect varia­ tions from one area to another w ithin the microscopic samples. For example, traces of glue and a varnish such as dammar applied in early restorations might be present only in the upper part of the sample. On the other hand, sam­ pling could have picked up traces of an under­ layer, such as the white isolating layer between the paint and ground. Finally, it has been sug­ gested that some materials from such a layer might migrate over time into the paint layer being sampled. Small amounts o f protein appearing in the samples could have originat­ ed in the white isolating layer rather than the paint itself. Underpaint layers, and possibly iso­ lating layers, containing egg protein have been observed in some early Netherlandish paint­ ings, particularly works of the Campin group, in which the paint layers themselves were exe­ cuted in oil.35 These analytical results, w hich were obtained using several different analytical tech­ niques, reaffirm the im portance o f careful interpretation of analytical data. Taken togeth­ er, the data confirm that the medium o f the Baltimore panels is not an emulsion: In an emulsion, substantial amounts of a water-based 112

THE MEDIUM OF A PRE-EYCKIAN A LTA RPIECE

protein medium such as egg would have been mixed into oil. It seems more likely that the very small amounts of proteins observed derived from one of the types of contamination sug­ gested above than that the artist added minis­ cule quantities of glue or egg to an oil medium. For practical purposes, this artist can be con­ sidered to have worked in oil paint. There are some discrepancies between these results and the report on the Antwerp panels. It should be noted that only very limited opportunities exist for safe sampling of paint­ ings, and thus directly comparable samples are often not available. Some differences may be explained by variations in the areas available for sampling; others, however, probably derive from differences in the analytical methods used or from the different conservation histories of the panels in two collections. Taken together, the results of the 1993 and 2000 analyses indicate that the Baltimore panels were executed in lin­ seed oil with trace amounts of pine resin. The very small amounts of dammar or protein pres­ ent may have originated in restorations or in the white isolating layer between the paint and ground. The study of the Antwerp panels also iden­ tified oil in a sample from the red skies o f the Christopher panel (comparable to the sample of the red sky in the Baltimore Baptism). Analysis of the Walters panel, however, also suggests the use of oil with traces of pine resin in the ultra­ marine blue draperies o f the Virgin (painted directly over the ground and isolating layer) and in the orange cloth of honor (painted over gilding). The Antwerp sample most compara­ ble to those areas was from the Nativity— the ultramarine blue sky painted over gilding— where the analysis by Thissen and Kockaert indicated a tempera medium. Where the pres­ ent study identified linseed oil and a trace of pine resin in the Baltimore sample o f white paint from the throne in the Annunciation, Kockaert reported a protein-oil emulsion in the whitish underlayer o f the rocks on the Christopher panel, the most comparable Antwerp sample. Finally, the analysis in 2000 of the skin tone in the Baltimore Crucifixion panel indi­ cated the use of linseed oil (this analysis did not test for resins); again, if egg was present, it was a minor component. In the most comparable

sample from the Antwerp panels, also a skin tone, the published analysis reports a protein medium with some oil added to it. If the iso­ lating layer of the altarpiece did, in fact, include some egg medium, this might explain some of the variations in interpretation. Incorporation o f this isolating layer into samples o f the Antwerp paint layers, particularly those that lie directly over the layer, could have contributed to the proteins observed in analysis. We conclude from the present analysis that the Baltimore paintings, rather than being exe­ cuted in a range of protein-oil mixtures, which suggests an emulsion technique, were painted in a medium that was primarily linseed oil. Although the thick handling of the orange in the cloth o f honor and the slight awkward­ ness of details such as the red aureole of God the Father in the Baptism may indicate that this artist was not yet fluent in the oil medium, the evidence does not suggest a tentative tran­ sitional technique that mixed a new medium into the old.

C o m p a r iso n w ith Tw o C o n te m p o ra r y Paintings

The materials and techniques of Italian paint­ ings from around 1400 are much better under­ stood than are the techniques of the few surviving N orthern paintings from that peri­ od.36 Even though a range of technical stud­ ies is now available, technical research on N orthern paintings has not progressed to the point that these works can be firmly associat­ ed w ith a geographic region by features of materials and painting technique. Although it is well known that the dominant painting tech­ nique in Italy changed from egg tempera to oil painting, this transition cannot be taken as the model for the development o f painting tech­ nique throughout Europe. Two recent publications, however, do allow comparison of the Walters Annunciation, Baptism, and Crucifixion with two almost-contemporary N orthern works whose diverse materials and techniques illustrate the complex technical influ­ ences in play in the International style. Leopold Kockaert has studied Melchior Broederlam’s exterior wings for the Crucifixion Altarpiece in

Dijon, Flemish paintings commissioned by Philip the Bold of Burgundy.37 In addition, the Wilton Diptych, an English painting with stylistic asso­ ciations with Italy, France, Bohemia, and the Lower Rhine, has recently been the subject of exhaustive historical and technical study in con­ nection with an exhibition at the National Gallery, L o n d o n .S o m e features of these paint­ ings are typical of Northern European practice in the fifteenth century, but other aspects seem reminiscent of Southern, or Italian, practice. Like virtually all N orthern fifteenth-century paintings, the Walters panels and both o f these works were executed on oak panels prepared w ith chalk grounds rather than the gypsum (gesso) grounds typical of Italy. Unlike the Wal­ ters panels, where the ground lies directly over the wood, both the Broederlam wings and the W ilton Diptych have an intermediate layer between panel and ground. The Broederlam panels were prepared with linen cloth, while the Wilton Diptych has a layer of what appears to be parchment fibers over the panel. A fab­ ric layer is commonly found over the poplar panels o f Italian paintings. But while this pro­ cedure is rarely found in fifteenth-century Netherlandish paintings (which use oak, a more close-grained wood, as the support),39 both fabric and parchment reinforcements have been observed on a number of pre-Eyckian panels from around 1400.40 Like the Walters panels (and many Italian paintings), both works are richly gilded, with a red bole preparation below the gold leaf; none o f these works renders metallic surfaces with illusionistic painting. As in many fifteenth-century Netherlandish paintings, the chalk ground of the Walters pan­ els was isolated from the oil paint (except in gilded areas) by an oil-rich sealing layer pig­ mented with white lead and chalk. Egg tem­ pera paintings, typical of Italian practice, usually have no such isolating layer since the technique requires that the ground absorb water from the paint, drying each stroke as it is laid down.The paint of the Wilton Diptych was laid down in the fine hatched strokes typical of tempera.The cross sections show no evidence of an isolating layer over the ground, and GC-MS analysis con­ firmed the use of a tempera medium. Kockaert reported that in the Broederlam wings, micro­ chemical analysis indicated the use of a mediTHE MEDIUM OF A PRE-EYCKIAN ALTARPIECE

113

um close to egg tempera. He also reported, however, the presence of an isolating layer con­ taining white lead over the ground. As in the Antwerp—Baltimore panels, this isolating layer is not present beneath the gilding. Kockaert’s analysis characterized the medium ofB ro ederlam’s isolating layer as an emulsion of protein and oil. It was not possible to do analysis o f the isolating layer alone in the Baltimore panels; however, as discussed above, it is possible that this layer also included some egg medium. In another echo of Italian painting, skin tones in both the Broederlam wings and the Wilton Diptych have a greenish underpaint: Broeder­ lam used a mixture of white lead, copper green, and charcoal black; the artist of the Wilton Dip­ tych used green earth w ith w hite lead. The Antwerp—Baltimore panels had no such under­ paint beneath the skin tones. In a final parallel with Italian materials, both Broederlam and the artist of the Wilton Dip­ tych used lead-tin yellow Type II rather than Type I, commonly found in N orthern paint­ ings. This finding, however, cannot be com­ pared to the Antwerp—Baltimore paintings, since lead-tin yellow has not been identified in any of the panels. W ithout further technical studies of the few surviving Northern easel paintings from around 1400, we cannot speculate on these intriguing juxtapositions: materials and techniques that are generally considered typical of N orthern prac­ tice combined with those characteristic of Italy. It remains to be seen whether these juxtaposi­ tions represent regional painting practices or per­ sonal choices of techniques that Broederlam and the artist of the Wilton Diptych encountered on their travels and then incorporated into their established painting practices.

C onclu sion s

The present study suggests that, unlike those of the Broederlam wings or the Wilton Dip­ tych, the materials of the Antwerp—Baltimore quadriptych are more consistent with fifteenthcentury Netherlandish practice than has pre­ viously been realized. Yet the handling o f the materials seems comparatively archaic. 114

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T he artist prepared an oak panel w ith a chalk-glue ground. The ground was sealed and given a brilliant, reflective painting sur­ face w ith an oil-rich layer o f white lead and chalk (possibly w ith an admixture o f egg). The paintings were extensively gilded and tooled. Perhaps through a com bination o f artistic conservatism and lack o f familiarity with the possibilities o f the oil medium, this artist continued to represent details such as gold brocade by gilding over bole, rather than by suggesting its appearance illusionistically w ith yellow paint as Van Eyck and his con­ temporaries did. The paint medium is apparently linseed oil with traces o f pine resin, and the artist appre­ ciated and exploited the creamy handling properties o f the m edium , although some awkwardness is reflected in the handling of the fairly thick paint. Although the artist used glazing for some naturalistic effects, most areas do not exploit oil’s ability to render rich, deeply saturated colors. Indeed, the artist seems deliberately to have undercut this sat­ uration by mixing a substantial proportion of w hite lead into the colors. In this way, although painted in oil, the paintings retain the aesthetic convention o f clear, unsaturat­ ed colors that is often associated w ith the optical properties o f egg tempera or manu­ script illumination. Although analysis has now revealed that the painting materials o f the Antwerp-Baltimore quadriptych are remarkably similar to those of fifteenth-century Flemish practice, the style o f the paintings seems strikingly archaic when compared with paintings of the following gen­ eration. The difference in appearance has con­ tributed to an assumption that the materials used, in particular the painting medium, must also differ. This technical study, however, sug­ gests that the difference in appearance can be traced to the handling o f the materials. The handling reveals that in aesthetic terms, this artist was rooted in the fourteenth century. Although oil paint was used in the A ntw erpBaltimore quadriptych a generation before its presumed inventor, Jan van Eyck, was at work, it was Van Eyck and his contemporaries who exploited the properties of the oil medium in illusionistic representation.

NOTES

*This paper was previously published in a somewhat dif­ ferent form as Gifford 1995a. The results of the 1993 analysis were first presented in a paper read at the ICOM Committee for Conservation Tenth Triennial Meeting, Washington, D.C.; see Gifford et al. 1993. **Now at Candle Light Productions, Playa del Rey, Calif. 1. For a review o f this history, see Brinkman 1993; Roy 2000; and White 2000.

results of L. Kockaert’s analysis of Melchior Broederlam’s exte­ rior wings for the Crucifixion Altarpiece in Dijon. Using microchemical tests, Kockaert found predominantly protein-based media (tentatively identified as whole egg) in opaque paints. Glazes included an ultramarine glaze in protein distemper (ten­ tatively identified as egg white) ; red, brown, and yellow glazes in an oil medium; and green glazes typical of copper resinate. For a preliminary report on these findings, see also Kockaert 1984.

2. Nieuwdorp, Guislain-Witterman, and Kockaert 1984—85; Nieuwdorp 1994.

19. White 1995; Scharff 1995; Liversidge and Binski 1995; Binski and Freestone 1995; Villers, van Heemstra, and Rey­ nolds 1997.

3. The Nativity, The Resurrection, Saint Christopher, Museum Mayer van den Bergh, Antwerp, 374A-C. Panels B and C represent the two sides of one of the panels’ wings. Ah three panels measure 38 x 26.5 cm.

20. N ieuw dorp, G uislain-W itterm an, and Kockaert 1984-85,93-97.

21. The layer structure of the paintings was studied using microscopic paint samples taken from the edges of existing paint losses. These were mounted in polyester, then ground and polished to expose the layers in cross section for micro­ 5. Theophilus reprint 1979, 27—28.The author discusses oil scopical examination by reflected light. Pigments were iden­ as a medium in the specialized case of details painted over tin tified by polarizing light microscopy of dispersed samples leaf; see 33—34. mounted for transmitted light examination and by energydispersive X-ray analysis (EDX) of the cross sections using a 6. Ibid., 32. JEOL electron microprobe at the Electron Microscope Central 7. White 1995. Facility of the University of Maryland at College Park.EMG is most grateful to Myron Eugene Taylor, director of the facil­ 8. Scharff 1995. ity, and to Helaleh Maghsoudlou, graduate research assistant, for their assistance. 9. Liversidge and Binski 1995; Binski and Freestone 1995. 4. For further information on the original grouping of the panels in a quadriptych, see Nieuwdorp 1994.

10. Vihers, van Heemstra, and Reynolds 1997.

11. Plahter 1995. 12. Borradaile and Borradaile 1966, 54—55; Merrifield 1967 (see voi. 1, Manuscripts ofJehan Le Begue, 116-64). The “Book of Master Peter of St.Audemar on Making Colours,” 232—33, makes frequent reference to oil as a medium for painting “on wood.” Le Begue’s transcript of Eraclius cites oil as one pos­ sible painting medium. 13. Jan van Eyck, The Madonna with CanonJoris van der Paele, Groeningemuseum, Bruges, 0.161. 14. Roy 2000. 15. See Campbell, Foister, and Roy 1997,40—43 and 53-55, table. 16. Such techniques include gas chromatography and highpressure liquid chromatography, used in the present study and discussed below, as well as thin-layer chromatography. 17. Stain can be trapped in the surface of rough-textured samples, giving the impression of a positive reaction. In addi­ tion, certain stains used in an acidic formulation can react with carbonate paints, such as white lead, falsely suggesting a spot­ ty positive reaction in those layers. 18. Colman 1960 reported the use in different areas of the paintings of a water-soluble medium (hence, not oil), an oil medium, and a medium that yielded ambiguous results. The method o f analysis and the analyst were not specified. Goetghebeur et al. 1976—77 reported that microchemical analy­ sis identified predominantly emulsion media based on protein with a little oil. Comblen-Sonkes 1986, 70-79, published the

22. Suzanne Quillen Lomax o f the Scientific Research D epartm ent o f the National Gallery of Art analyzed hydrolyzed and methylated samples by gas chromatography (using a Perkin Elmer Autosystem gas chromatograph) and GC-MS (using aVarian 3700 gas chromatograph and Finnigan ion trap mass spectrometer). See Lomax 1993. 23. Susana Halpine of the Scientific Research Department of the National Gallery of Art prepared samples by cold-water extraction followed by hydrolysis and PITC derivitization.The samples were analyzed by AAA using a Hewlett Packard 1090 HPLC system. See Halpine 1993. For the cold-water extrac­ tion method, see Halpine 1995. 24. Analysis was carried out by Suzanne Lomax using the following procedure, developed at the Getty Conservation Institute. The samples were weighed on an ultramicrobalance, then placed in 0.1 mL conical reaction vials (Alltech). Sufficient norleucine solution was added to give a final concentration of 50 ppm in the final injection volume. Fifty pL o f 6.ON hydrochloric acid was added; the vials were capped with Mininert valves and evacuated using a vacuum pump. The vials were heated at 105°C for 24 hours in an oven, removed from heat, and let stand until cool. The vials were then centrifuged, and evaporated to dryness using a nitrogen stream while warm­ ing to 60°C.The vials were rinsed sequentially with 40 pL of high-purity water and with 40 pL of 200-proof ethanol, evap­ orating the contents to dryness after each rinsing. One pL of silylating reagent was added per 2 pg of sample.The silylating reagent is prepared by mixing 300 mL of M TBSTFA/ TBDMCS with 700 mL of a solution made from 40 mg of pyridine hydrochloride per mL of pyridine. GC-MS condi­ tions: 30 M x 0.32 mm x 0.25 pm DB-5MS column (from J&W Scientific); helium carrier set to 1.7 mL/min; splitless

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injection; GC oven temperature program: 80°C for 1 min; 20°C/m to 2S0°C; isothermal for 3 min. Injector temperature 260°C. See Lomax 2000. 25. Michael Schilling carried out this investigation using the procedure described in Schilling and Khanjian 1996 and Lomax 2000. See also Schilling and Lomax 2000. 26. Bone black was confirmed by the presence of phos­ phorous in the EDX spectrum for the layer. 27. Nieuwdorp, Guislain-Witterman, and Kockaert 1984-85,93-97. 28. The identification of the medium of the ground was made by staining cross sections w ith amido black stain. Amido black is a visible-light stain that is positive for pro­ teins. The neutral pH formulation used in this study is most sensitive to glue and least likely to erode chalk layers in cross sections. 29. The results of stains for fatty acids (oils) can often be more ambiguous than those of protein stains. In this case, stain­ ing of cross sections with 2,7 dichlorofluorescein (a fluores­ cent stain) gave a strongly positive reaction in the isolating layer. 30. Lomax 1993. This report identified a ratio of methyl palmitate to methyl stearate typical of linseed oil, as well as peaks with retention times characteristic of diterpenoid resins that may indicate the presence of material such as pine resin. 31. Halpine 1993.

section does not prove that this top layer is not an original ele­ ment, it seems most likely that the proteinaceous coating remains from gelatin or animal glue applied during an earlier restoration to consolidate the fragile orange paint, which is weakly adhered to the gold leaf below. 33. The sample was stained for fatty acids with 2,7 dichlo­ rofluorescein. Ponceau S, a visible-light stain that is positive for proteins, was used for this sample because its pink color was easily seen against the blue paint layers. 34. By contrast, Jan van Eyck, working a generation later, appears to have laid in blue draperies with oil paint followed by a glue-based ultramarine glaze. Coremans et al. 1953,70—71; Coremans 1954, 150.The same medium has been identified in the blue glaze of the Virgin’s mantle in Van Eyck’s Annunciation in the National Gallery of Art, Washington, D.C. For a preliminary report on the technical study of this paint­ ing, see Gifford 1995b. A complete report on the study will appear at a later time. 35. White 1996; Campbell, Foister, and Roy 1997, 23. 36. For recent research on the materials and techniques of Italian paintings, see especially Bomford et al. 1989. 37. Comblen-Sonkes 1986; Kockaert 1984. 38. Gordon 1993. References to the analysis of this paint­ ing in the following section of this paper are based on the essay in that catalogue: see Gordon, Roy, and Wyld 1993. 39. Gordon, Roy, and Wyld 1993, 84, n. 49.

Van Schoute andVerougstraete 1995.These authors sug­ 32. The orange paint layer did not show a positive reaction 40. to the protein stain, amido black (consistent with the GC-MS gest (p. 377) that the absence of fabric or parchment layers finding that it contains oil and resin) ; however, a transparent, reinforcing the panel in later paintings might result from the increased use of superior oak imported from the Baltic rather unpigmented layer on top of this paint stained strongly for than local supplies. protein (consistent with the AAA results). Although this cross

116

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D igital Im agin g f o r the S t u d y o f Paintings: E xp eriences a t the S t r a u s C enter for C onservation H enry Lie Harvard University A r t M useums

Introduction

Studies in the visual arts have been assisted by advances in digital imaging technology for approximately twelve years. Projects generally fall into four categories: documentation, visu­ alization, image analysis, and image distribution. Enhancements in documentation have ranged from simple improvements in annotating pho­ tographs of the condition of paintings to sophis­ ticated research into accurate color imaging of painted surfaces.1 Computer visualization proj­ ects have allowed conservators and curators to approximate the effects o f cleaning artworks before the actual cleaning begins and to simu­ late the appearance of mounting and framing artworks during the decision-making process of how to do so. Image analysis technology has been used in innovative ways to quantify tonal and textural aspects of artwork surfaces and to mea­ sure changes related to deterioration and treat­ ment.2 Finally, the distribution of digital images is changing the nature of public access to col­ lections. Stimulated by the explosive growth of the Internet, the task of digitizing images of art­ works is under way at an increasing number of institutions and will eventually lead to unprece­ dented systems for scholarly study. In addition to caring for the collections at the Harvard University Art Museums, the Straus Center for Conservation serves as a regional treatment center and offers training for advanced interns in conservation. Although no computer specialists are on its staff, its conser­ vators and researchers have made use of com­ puters since 1990 to assist in a variety of documentation and visualization projects. These have included image annotation for condition documentation, simulations of mounting and framing, and enhancements of infrared refl.eetograms (IRRs) and other technical images.

This paper will discuss methods used at the Center to produce IR R and X-radiographic composites and a new m ethod for viewing combinations of technical images of paintings.

Infrared M osaicking

Vidicons (infrared video cameras) used for examining the underdrawings of paintings are sensitive at longer wavelengths than photo­ graphic infrared films, which have been used for the same purpose. Because of this, infrared video cameras are better able to penetrate the paint layers that usually obscure an underdrawing. Unfortunately, the relatively low resolution of both the NTSC (American) and PAL (Euro­ pean) video standards does not offer adequate detail to view even small paintings all at once. Since the development of infrared composites byj. R. J. van Asperen de Boer in the late 1960s, sequential views of portions of paintings have been combined to create high-resolution com­ posites by photographing the video monitor with 35-mm film and cutting and pasting prints from these films to an overall backing.3 The process is laborious, and the composites often lack precision and draw undue attention to the process used to create them. Figure 1 is an exam­ ple of a traditional composite that suffers from this problem. Depending on the quality of the film images and the care taken during darkroom and assembly procedures, composites can be made that are easier to read than this example. In the 1980s and early 1990s, two types of specialized software were developed to capture and assemble multiple IR R images.4 Mosart, an M S-DOS-based application, is no longer used due to rapid changes in hardware and operating systems. The other software, known as VIPS (Visual Image Processing System), is a DIGITAL IMAGING ATTHE STRAUS CENTER

117

Fig. 1. A traditional IR R composite o f a detail o f Jan Provoosts Dispute of St. Catherine ofAlexandria (Museum Boijmans Van Beuningen, Rotterdam , 1682) made by trim m ing and gluing photographic prints to a paperboard backing. Laborious darkroom work would be nec­ essary to improve the readability o f such a composite. (IR R :J. R .J. van Asperen de B o er/R o n Spronk)

component of the European U nion’sVASARI (Visual Arts System for the Archiving and Retrieval o f Images) Project. It is now used by only a small number of institutions because of the intimidating nature of the U N IX oper­ ating system.The Straus Center has never used Mosart, but the use of VIPS for selected proj­ ects is discussed in a later section. In 1991, experiments at the Straus Center for Conservation with off-the-shelf products led to the use of Adobe Photoshop image-manipula­ tion software to create high-resolution com­ posites of multiple infrared images.Though not designed for this purpose, Photoshop’s broad set of tools can be used to create high-quality com­ posites in a fraction of the time required by the cutting and gluing method. Composites of forty to sixty images can be completed within three to five hours, and images are easily enhanced prior to printing. Although it may eventually be 118

DIGITAL IMAGING AT THE STRAUS CENTER

1

2

3

4

Fig. 2. Individual IR R images from a detail o f Jan Provoosts LastJudgment (Detroit Institute of Arts, 89.35). The system of letters and numerals for rows and columns determines the file names for each of the twenty-eight digital documents prior to the mosaicking process.

replaced by the VASARI system, Photoshop is now used for creating composites and other types of documents at a growing number of institu­ tions. Its professional quality, frequent upgrades, and availability on multiple platforms will ensure its usefulness for some years to come. Below is a description of the use of Photoshop for cre­ ating infrared composites; X-radiographic com­ posites are discussed in a later section. Regular improvements in the program create opportu­ nities for users to improve on this process as the Photoshop software itself evolves, and it is like­ ly that individual strategies will differ from insti­ tution to institution. In order to facilitate the assembly of the com­ posite, each infrared image is acquired in digi­ tal format using a capture board in the computer and is saved as an individual 640 x 480 pixel doc­ ument named after its position in the grid of vertical columns and horizontal rows (fig. 2).

Fig. 3. IR R s are placed sequentially into the composite image and shifted into alignment using the mouse or the keyboards arrow keys. Each image remains in its own layer in the composite document and can be adjusted in value to match adjacent images.

As can be seen in this illustration of twenty-eight captures from a detail of Jan Provoost’s Detroit LastJudgment, a substantial overlap between adja­ cent frames is required to facilitate the correc­ tion and assembly process described below. A new Photoshop document is created with adequate vertical and horizontal pixel dimen­ sions to accommodate all of the individual images acquired from the painting. Before being pasted into this large document, each image is modified to correct distortions resulting from imperfections in the camera system. Although the camera and lens cause some geometric distortion, a far greater problem is the value distortion visible in the individual frames of many traditional composites, such as figure 1. Even with their automatic gain (brightness) con­

trols turned off, vidicons tend to react to bright­ ness level changes as they point to different por­ tions of the painting, and the outer edges of each frame are frequently distorted in value com­ pared to the centers. By capturing an image with the camera pointed at a featureless surface, such as a photographic gray card, these value distor­ tions can be quantified so that corrections can be made in each image gathered from the paint­ ing. Using the subtract function in the calcula­ tions menu, Photoshop compares each image with a gray-card image to correct value distor­ tions. Approximately 65-75 pixels are then cropped from each of the four sides of the cor­ rected image to remove areas at the extremi­ ties that may still show imperfections. The corrected and cropped images are placed sequentially into individual layers in the new DIGITAL IMAGING ATTHE STRAUS CENTER

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Fig. 4. Problem areas within an image can be corrected by selecting the appropriate layer and using the lasso tool to select the area in need o f correction. The periphery o f the selection can be made to blend gradually into the rest o f image c2 by setting the tool to feather the selection over 30-40 pixels. In histogram B, the middle slider control has been moved too far to the right to clearly demonstrate the effect o f making such an adjustment.

composite document (fig. 3).Tools in Photo­ shop allow each image to be nudged into place horizontally and vertically using the mouse and the keyboard’s arrow keys. Once the composite is complete, junctures between images are likely to be visible in a few areas. These relatively subtle problems do not interfere w ith viewing and interpreting the image, and it could be argued that a compos­ ite left at this stage is a particularly honest rep­ 120

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resentation of the raw data. If for aesthetic rea­ sons there is a desire to improve some areas, they can be selected and adjusted. As each frame is added, Photoshop maintains a distinct layer in the document for that frame.5 This allows for subsequent corrections in brightness and contrast in individual frames by selecting the appropriate layer from the layers palette. Figure 4 illustrates how a small section of an individual frame can also be corrected. In spite

Fig. 5. Corrected composite o f a detail o f Jan Provoost’s Last Judgment. (IR R and digital composite: R o n Spronk; the individual frames in figs. 2—5 were made using the Detroit Institute o f Art’s Hamamatsu camera.)

of the gray-card corrections that were applied to each image, figure 3 shows a distracting val­ ue distortion in the angel’s upper elbow in frame c2.To correct this, layer c2 is selected and the lasso tool is used to encircle the top right corner of frame c2.The lasso tool is set to feath­ er the boundary of the selection over a distance o f 40 pixels so that the value changes made to the corner of c2 will have a smooth gradation within c2. A histogram, labeled A, is displayed showing the original values of the pixels in the

selection. A second histogram, labeled B, shows the middle, or gamma, slider shifted to the right, therein lowering the overall value o f most of the selected pixels to about half. For the pur­ poses o f illustrating the use o f this tool, this overcorrection is visible in the saint’s upper elbow, which has changed from too fight to too dark. A perfect correction can be made by mov­ ing the gamma slider partway back toward its original position in histogram A. Figure 5 shows the corrected assembly. DIGITAL IMAGING AT THE STRAUS CENTER

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Im age A cq u isition

This paper will not attempt to discuss recent im portant research at other institutions that seeks to better define optimal wavelength ranges for acquiring IR R s from various painting types.6 However, the physical means of acqui­ sition should be mentioned, since various fac­ tors have significant effects on the success of the assembly process. Since the Photoshop-based assembly process does not apply geometric distortions to form perfect matches between adjacent images, it is particularly important to capture sequences of images in a manner that minimizes geometric problems such as parallax, the apparent con­ vergence of parallel fines when viewed at angles other than 90 degrees. Mosart had the ability to “rubber sheet,” or stretch, images to force a perfect fit, but with this or any assembly sys­ tem, such rearrangements of information should be kept to a minimum by optimizing the cam­ era and image-capturing set-up. W ith lead-sulfide, tube-based vidicons such as those made by Hamamatsu, a greater degree of camera-related distortion— geometric dis­ tortion and value distortion— occurs at the periphery of each image. To eliminate some o f this problem, each frame is cropped sub­ stantially. A 490 X 350 pixel rectangle is saved from each 640 x 480 pixel image.The area used may be slightly off-center if prior tests indicate that more camera distortion is present at one side or another o f each frame. Such tests are easily conducted by imaging a sheet o f graph paper and a photographic gray card. In order to avoid problems o f parallax, the camera must be carefully aligned. Although the plane o f the painting should be general­ ly perpendicular to the axis o f the camera, misalignment of the painting is not the cause o f poor matches betw een data in adjacent frames. Rather, the perpendicular alignment o f the camera axis with the plane o f the ver­ tical and horizontal scanning m otion is the critical step to preventing parallax problems betw een adjacent frames. The nonplanar nature o f most paintings usually makes the positioning of the painting a somewhat sub­ jective approximation. 122

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Fig. 6.The painting is secured to the enlarged shelf and backboard o f a manual crank easel. Vertical movement is controlled by the crank and horizontal by sliding the shelf and backboard left and right. The camera, which is stationary, is mounted on an optical tilt stage for align­ ment; the stage is m ounted on a rail to control the dis­ tance to the painting.

To facilitate fine camera adjustments, our infrared camera is mounted on a tilt stage with three adjustment knobs that allow control of tilt and rotation in all directions.The stage is mount­ ed on an optical rail, which is perpendicular to the painting and is used to adjust the distance to it.7W hen motion is defined by the plane of an easel transporting a painting, an alignment device such as Zig-Align8 (originally designed to align darkroom enlargers with easels) can be used quickly and accurately to set the camera per­ pendicular to the plane of x and y translation. The knobs on the optical stage are used to make fine adjustments while viewing through an align­ ment window in the device. In addition to pro­ viding precise alignment, the system removes some of the nerve-wracking aspects of the image acquisition procedure, since the camera can be easily checked or adjusted if there is any con­ cern that the set-up might have been disturbed during the scanning process. Most o f the reflectograms made thus far in the Straus C enter have employed a moving

easel and a stationary camera. Although motordriven easels are available, we have had good success with a modified, manually operated easel (fig. 6).W ith a moving easel, the vidicon is positioned on its optical tilt stage and rail on a table w ith feet that adjust to provide rough alignment. The feet can be fitted into small inserts in the floor so that when the sys­ tem is removed to clear the room for other functions, the set-up can be easily and accu­ rately repositioned.The painting is moved hor­ izontally on a tray equipped w ith a tall backboard, which slides on the shelf support o f the easel. Vertical m ovement is achieved by using the easel’s crank mechanism. Since the backboard and tray, which support the painting, are precisely aligned w ith the axes o f movement, the secondary m irror o f the Zig-AJign device is held against the backboard, not the irregular surface o f the painting, dur­ ing alignment of the camera.The easel, which was not made for this application, has been reinforced to lessen unpredictable shifting that would affect alignment. During the initial camera survey o f a paint­ ing, a camera position is chosen that will pro­ vide adequate resolution o f the features in question.Then, horizontal and vertical transla­ tion increments are determ ined by a set of interchangeable scales held in place with Vel­ cro (fig. 7). Each pair of scales offers increments that are appropriate for set camera-to-painting distances as marked on the optical rail.The set distances are close enough to one another that there is little need for intermediate positions. If fine detail revealing the character of the lines of the underdrawing is required, the minimum distance of 30 cm (from the Hamamatsu vidi­ con to the painting) is selected, and horizon­ tal and vertical translations of 3 and 2 cm are made using the appropriate pair of scales. Although a cam era-to-painting distance o f 43 cm yielding translations o f 5 cm (horizon­ tal) and 3.3 cm (vertical) is most common, the camera is occasionally backed away so that hor­ izontal increments of 10 cm can be used. Man­ ual movement o f the painting to match positions on the scales need not be exact since the overlap of adjacent frames can vary slight­ ly without affecting the assembly process. After cropping approximately 75 pixels from the sides and 65 pixels from the top and bottom of each

Fig. 7. Depending on the distance between the camera and painting, different pairs o f scales are attached to the easel w ith Velcro to control the increments o f vertical and horizontal movement.

frame, the overlap between adjacent frames needs to be about 80 pixels in order for matching features in both frames to be easily located during assembly. These standards for cropping and overlap were used to determine the incre­ ments marked on each pair o f translation scales. With this system for acquisition, it is not nec­ essary to carefully plan translation increments to achieve a specific number of frames with a specific overlap between frames. Instead, efforts can be concentrated on the all-important ques­ tion o f which o f the set camera-to-painting distances provides the resolution to give us the information we need. Then, the correspond­ ing translation scales are attached, and the acqui­ sition process starts at the top left and marches horizontally and vertically across the surface. If the last frames on the right and the bottom include little of the painting and mostly backDIGITAL IMAGING AT THE STRAUS CENTER

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Fig. 8. M oving the camera instead o f the painting allows imaging o f large paintings on a relatively small wall. A m otorized carriage moves the camera vertically and horizontally in increments appropriate for the camera’s dis­ tance to the painting.

ground, the only result is a small amount of wasted disk storage space. The sensitivity control (which controls the sensitivity of the tube to light) on the Hama­ matsu vidicon is adjusted as described in the manufacturers manual.Adjustment depends on the level o f illum ination and the reflective properties of the majority of the paintings sur­ face, with particular weighting given to areas o f special importance. In most cases, the set­ tings are kept the same during the entire acqui­ sition process in order to maintain as much consistency between frames and to facilitate the assembly process. The camera’s gain and offset settings (which control brightness and contrast) are generally kept as low as possible. Although this results in raw data that are low in contrast, the resulting brightness o f each frame from edge to edge is much more con­ sistent. Contrast adjustments are easily made to the final composite. 124

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The settings used to control the camera along with many other details o f the physical set-up in the laboratory are recorded on a form as a word processing document. This document is printed and filed and is also saved on disk with the raw data files from the acquisition process. The information can be of immediate impor­ tance if any section o f the painting needs to be acquired a second time or if problems asso­ ciated with an initial attempt require adjust­ ment and a second complete acquisition session. Data such as camera type, lens, filter, and illu­ mination can also be of importance in inter­ preting the appearance o f images many years in the future.

A n Im proved IR R Scanning and A cq u isition System

In 1996, engineer Nathan L. Hazen and Straus C enter staff designed and installed an

Fig. 10.The carriage’s camera mounting plate supports the same optical tilt stage and rail as was used in the easel system described above, allowing accurate alignment and adjustments in the distance to the painting.

Fig. 9 .The camera carriage is guided by a rail attached to the floor, and a column controls vertical movement ot the camera mounting plate. Commands are sent from the computer to move the camera and carriage in appro­ priate increments. Alternatively, the m otor drives can be disconnected to allow manual movement o f the camera and carriage.

improved scanning carriage for the department’s newly renovated laboratories.9 In the new acquisition system, the painting is stationary, and a camera transport system scans the surface of the work.This system offers advantages over the moving easel with regard to lighting, safe­ ty, and precision. The carriage allows for the imaging of flat artworks measuring up to 6 x 9 feet on a wall measuring only 7.5 x 12 feet (fig. 8); moving the painting instead of the cam­ era required twice as much ceiling height to image a large painting. The desire to conserve space at the Center was partly responsible for this efficient use of a small room and the devel­ opment of the new scanning carriage. A larger space and minor modifications to the carriage design would make the system capable of work­ ing with much larger paintings.

The device consists of a cart guided by a floor rail parallel to the painting and anchored to fit­ tings in the floor (figs. 9—10). Motors control the horizontal movement along this rail (the x axis) and the vertical movement of the cam­ era platform, which is guided by a vertical col­ umn (the y axis). The camera platform and camera are counterweighted using a lead-filled canister housed in a vertical tube adjacent to the vertical column. Multiple sets o f fittings m ounted flush w ith the surface o f the floor allow for easy repositioning of the floor rail and carriage to provide greater or lesser distance to the painting or to view paintings in transmit­ ted light, where lights are placed behind rather than in front of the painting.10The same opti­ cal rail and tilt stage described for the earlier system is used for camera alignment and for positioning in the z axis closer to or farther from the painting. The controllers for the motors are operat­ ed by relatively simple commands sent via the com puter’s serial port. After the camera has been positioned at the best viewing distance (the z axis on the optical rail), the keyboard’s arrow keys are set to send code to the con­ trollers, which move the camera the appro­ priate distance and direction.The motors can also be easily disengaged from the floor rail and vertical column to allow completely man­ ual manipulation of the camera position. Man­ ual positioning is usually the simplest way to DIGITAL IMAGING AT THE STRAUS CENTER

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Fig. 11. A com posite o f tw enty-one infrared images o f the Antw erp School Arrest of Christ, B usch-Reisinger Museum, Harvard University, B R 52.15.T he images were made using the InfraC A M -SW IR (shortwave infrared reflectography video camera) from Inframetrics, Inc. (now FLIR Systems).The PtSi detector used in this device offers excellent penetration o f paint layers. T he limited resolution o f the detector (256 x 256 pixels) is overcome by com bining as many images as are needed to obtain the desired degree o f detail. (IR R and digital composite: H enry Lie)

scan various parts o f a painting during a pre­ liminary examination. Although not portable in the usual sense, the carriage can be easily detached from the floor rail and rolled to another location. Fixing the floor rail to a gallery floor could allow use of the system in an exhibition area.

selves emit energy in the thermal region of the spectrum. External filters limit the range of wavelengths detected to a smaller band with­ in the 1.1 to 2.5 micron range and can be used to optimize the visibility o f underdrawings. From our own experiences, the best results are frequently obtained in the 1.5 to 2.0 micron range.

Im proved Infrared Cam eras

In addition to improved dynamic range and greater sensitivity in the 1.5 to 2.0 micron region, CCD cameras offer less geometric dis­ tortion and value distortion than tube-based cameras. This eliminates the irregular tonal quality o f most vidicon images, which, along w ith spatial distortions, complicates their assembly into high-resolution composites. However, unlike lead-sulfide vidicons, PtSi cameras are not sensitive below 1.1 microns. Ongoing research indicates that narrow-band filters in this region will assist in the identifi­ cation o f certain drawing m edia11 and that institutions purchasing PtSi cameras will con­ tinue to use their Hamamatsu vidicons for cer­ tain applications.

A new generation of infrared cameras based on charge-coupled devices (CCDs) rather than lead-sulfide camera tubes is now available.Those offering the greatest range in the infrared use platinum silicide (PtSi) C C D detectors. To operate, these detectors must be cooled to very low temperatures, either with liquid nitrogen or, more recently, electric cooling systems. PtSi detectors are sensitive from 1.1 microns and extend into the “thermal” region of the infrared to about 5 microns. Many applications, includ­ ing examinations of underdrawings, are opti­ mal between 1.1 and 2.5 microns. An internal filter to cut out wavelengths above this range is often provided to remove noise at the longer wavelengths. Such noise cannot be excluded using external auxiliary filters, since at room temperature, the surfaces o f the filters them­ 126

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In the time since the conference was held, many facilities including the Straus C enter have purchased IR video systems using plat-

inum silicide detectors. In 1999, the Straus Center began using a PtSi camera from Infra­ metrics, Inc. (now FLIR Systems).12 The InfraCAM—SW IR (shortwave infrared reflectography video camera) is compact, operates on batteries, and weighs only 1.36 kilograms. A detachable viewfinder allows for examina­ tions in the laboratory or gallery w ithout the need for a m onitor or computer. The system norm ally includes 1.1—1.4, 1.5—1.8, and 1.9—2.4 m icron bandpass filters, which are inserted into a slot in the lens and can be changed while operating the camera. Two auxiliary close-up lenses allow a field of view as small as 3 by 3 cm.The configuration most frequently used at the Center is with the clos­ er o f the two close-up lenses and the 1.5—1.8 micron filter.The relatively small (256 x 256 pixel) CCD array o f the camera is offset by the high quality o f the individual images. Unlike the vidicon, there is no need to crop distortions near the periphery o f each image, and composites o f a particular painting gen­ erally demand about the same num ber o f individual frames w ith either camera type. The InfraCAM’s greater sensitivity in the 1.5 to 2.0 micron region allows better penetra­ tion of some pigments and usually results in composites o f improved geometric accuracy and dynamic range. The camera mounts on the same tilt stage and camera transport sys­ tem described above. A composite o f twentyone separate details from the InfraCAM is shown in figure 11. Camera resolution has been a topic of great interest to scholars and scientists using infrared equipm ent. The best resolution possible is desirable for two reasons. First, w ith a cam­ era offering higher resolution, an operator using the camera at a distance close enough to provide adequate detail can examine a larg­ er area of a painting at a given time. Second, w hen creating a composite o f IR R images o f an entire painting, fewer images are need­ ed with a higher-resolution camera to achieve a given amount of detail. However, no videobased camera exists that is capable o f imag­ ing all o f even a relatively small painting at once. Even cameras of the best resolution must scan across the surface o f a painting, produc­ ing scores of individual images that then require assembly. The care taken in this process

is at least as important as camera resolution, dynamic range, and sensitivity in the 1.5 to 2.0 micron range. For this reason, all cameras benefit greatly from a precise, easy to use, and preferably repeatable acquisition system. In other words, an adequate scanning system off­ sets the limitations o f relatively low-resolu­ tion cameras. Two such systems (easel-based, which moved the painting, and carriage-based, which moved the camera) were described ear­ lier in this paper. An infrared composite from a third system, the MuSIS 2007 from Art Inno­ vations in the Netherlands, illustrates the res­ olution possible w ith a close-up lens and a good acquisition set-up (fig. 12).The CCD chip used for this device offers good resolu­ tion for a video-based device, but the resolu­ tion o f the composite is the result of accurate acquisition of twenty-four separate details. The close-up lens reveals the texture of the under­ drawn lines. Significant improvement in digital still cam­ eras for studio photography has also led to experimentation with these devices. Although the silicon CCD detectors in these cameras are sensitive only to a maximum of 1.1 microns, the cameras provide somewhat better results than traditional infrared film photography. Even at these shorter wavelengths, the pigment lay­ ers of many paintings are sufficiently transpar­ ent for underdrawing studies. W ith their significantly higher resolution detectors, they produce crisp images in a single shot, elimi­ nating the need to assemble multiple lowresolution video captures. Typically, these cameras have a built-in filter that cuts out all infrared light. Having ordered the Phase One LightPhase digital camera back without its nor­ mal filter, we are currently taking both infrared and daylight images by placing the appropriate filters in front o f the camera lens. The camera back, which is designed for use with Hasselblad and similar camera bodies, utilizes a 2000 x 3000 pixel detector and is sold primarily for studio photography as an alternative to mediumformat film cameras. Its dual IR and visible capabilities simplify the production of layered Photoshop images in these wavelengths, since a single setup can be used to provide two per­ fectly matched images. Because of the higher resolution provided by the LightPhase camera, it is usually possible to obtain excellent infrared DIGITAL IMAGINGATTHE STRAUS CENTER

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Fig. 12. Composite o f twenty-four infrared images from a 3 x 5 cm detail o f the Arrest of Christ.The high resolu­ tion o f this image illustrates how careful setup o f the acquisition system can provide exceptional detail in spite of the limitations o f video devices. A close-up lens on the Art Innovations MuSIS 2007 multispectral camera reveals the character o f underdrawn lines and the texture o f the white ground. (IR R and digital composite: Henry Lie)

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Fig. 13. Digital infrared photograph of the Arrest of Christ made with a single exposure using the Phase One LightPhase 2000 X 3000 pixel camera back on a Hasselblad camera body.

images with a single exposure (fig. 13). Using extension rings for close-up photography, we can achieve an extremely high degree of detail in the infrared (fig. 14). Such microscopic views of underdrawn lines can be helpful in further characterizing the drawing process and usual­ ly answer such questions as whether the draw­ ing was done in a dry or wet medium.

X -R a d io g ra p h C om p osites

Paintings large enough to require more than one 14x 1 7 inch X-radiographic film for doc­ umentation present mosaicking problems sim­ ilar to IRRs if an overall composite is required. The traditional means of creating a composite involves aligning films on a light box, marking

Fig. 14. Extreme close-up o f a detail of the Arrest of Christ made with a single exposure with the LightPhase/Hasselblad system using extension rings between the camera and lens.

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the areas of overlap, and removing excess por­ tions from adjacent films. This method can work well but is time consuming and at least partially destructive in terms o f the original resource material. Since the composite is not easily stored, it is usually disassembled and therefore difficult to view at a later date. Photographing the composite for publication is also problem­ atic, since most light boxes and films do not allow adequate rendering o f the information in the X-radiographs. By scanning each film, it is possible to create digital composites and avoid many o f these problems. The Center uses a Sharp JX 610 large-format flatbed scanner to scan X-radiographic films. The device uses CCD technology to acquire 10 bit per channel RGB color images or 10 bit grayscale images. The bit depth o f the scans is reduced to the standard of 8 bits when the data enters the computing environment. Even at 8 bits, most scans of X-radiographic materials fail to exhibit the full range of 256 gray values. However, most scans do display tremendous detail and reveal all o f the features important to the study ofpaintings.The 12 x 17 inch bed size requires two scans, each a little over seven inches wide, which are combined in Photo­ shop to reproduce the full 14-inch width of each film. This cumbersome extra step could be avoided by using a scanner designed specif­ ically for 14 x 17 inch X-radiographic films. Though expensive, these devices offer greater dynamic range and are capable of penetrating films with areas of substantial density. The Cen­ ter plans to digitize its Alan Burroughs Col­ lection of X-Radiographic Films of Paintings and will purchase a specialized scanner in the future. Scans at resolutions over 300 dots per inch (dpi) reproduce information in much greater detail than is normally needed for the study of paintings. Scans of 14 x 17 inch films at this resolution are 20 megabytes in size and can be useful w hen stored as single-film archives. Composites of several films are made from files that have been reduced in size. The degree of resolution reduction is dependent on the num­ ber of films in the composite, the content of the films, and the proposed use o f the com­ posite. Even large-format publications will accept full-page grayscale composite illustra­ 130

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tions no larger than about 15 megabytes.Thus, in creating composites for publication, scan­ ning resolutions can be considerably less than 300 dpi. Alternatively, high-resolution archived scans can be downsized prior to assembly. Even if online viewing rather than publication is the intended use of the composite, reduced reso­ lutions can be adequate for good scholarship and are easier to use. Once the appropriate resolution and file size for the individual films have been determined, the separate images can be assembled in Pho­ toshop in a manner very similar to that used in infrared assembly. N o corrections, such as the use of the gray-card images to remove irregu­ larities in the camera system, need normally be applied. However, even when great care is tak­ en to align the individual films prior to expo­ sure, small rotational differences usually exist between them that need correction. Using Photoshop’s info palette and the measure tool, it is easy to view the slope of a line between any two given points. N oting the difference in this slope for corresponding points along the edges of two overlapping films, the operator can eas­ ily rotate one o f the films by this amount to achieve alignment. If the painting’s surface is planer and each film is in good contact with it, the images will be a perfect map o f the features in the paint film. Features in the support that are not close to the paint film, such as nails or some aspects of the grain of the wood, will appear at differ­ ent locations in adjacent films if the X-ray source was moved relative to the painting for each film exposure. If many out-of-plane fea­ tures are present, the misalignment o f features at the joins between adjacent films can be con­ fusing. The problem can be eliminated by increasing the distance to the X-ray source to provide even exposure of the entire painting without having to move the source relative to the painting for the exposure of each film.

D o c u m e n t Layering in P h o to sh o p

A variety o f related technical images can be viewed in a single Photoshop docum ent by using the software s layers feature. Since infrared, ultraviolet, X-radiographic, and visible-light

photographs of a painting offer different infor­ mation about features over the same twodimensional surface, it makes sense to place such images over one another for comparison. Con­ trols in the layers palette allow individual lay­ ers to be reordered in the stack or turned on or off to make them visible or not visible, and a slider can be used to assign varying degrees of transparency to a selected layer. Changes in transparency, which are immediately visible as the slider is moved, allow more than one layer to be visible at a single time. The concept of placing technical informa­ tion into a layered format is not new. Infor­ m ation related to condition or to features visible in technical images has frequently been traced onto transparent mylar overlays, which can then be viewed on top o f a photograph of a painting.This provides a quick and poten­ tially accurate representation of the locations of related features.This type of system is inher­ ently limited to linear representations traced onto the mylar. Placing different images into layers o f a Photoshop document offers a great deal more than improved efficiency and a more finished product. Relatively inexpensive desktop computer systems now make it pos­ sible to view extremely high-resolution images with ease. W hen the entire image is visible in a win­ dow on the monitor, the overall composition can be viewed at the expense of seeing detailed information. By zooming in to an area of inter­ est, the potentially tremendous detail of a highresolution image is revealed. Easy-to-use controls make it simple to pan across the sur­ face at whatever magnification is most useful. W ith a variety of technical images stacked in the layers of a single document, the power of this viewing system increases exponentially. Instead of simple tracings of related images, the complete images themselves are readily avail­ able for overall or detailed viewing. Switching quickly back and forth between images, espe­ cially w hen viewing at high magnification, allows for revealing comparisons that would otherwise be difficult to imagine. Assigning transparency to a layer allows simultaneous viewing of features in different layers. Such combined views can be saved and printed for use as traditional documents on paper.

In order to produce a document of layered technical images, the individual images must be adjusted to match one another in both size and shape; in addition, as much as possible, a relatively consistent resolution is desirable for X-radiographic, IR R , and other types of images. Individual image size is the least diffi­ cult obstacle in producing a good layered doc­ ument. Examining the height-to-width ratios of each image inevitably reveals discrepancies in the shape of the image, and it is typical for the top, bottom, and sides o f the painting in each image to exhibit a variety of angles from the vertical and horizontal edges o f the document.This is due to the diverse means by which images are acquired and the fact that each is very likely to introduce some degree o f dis­ tortion. The X-radiographic image, especially in the case of smaller paintings where only a single film is required, is likely to offer the most accurate map o f the painting’s surface. This makes it the best candidate to serve as a tem­ plate around which all of the other images can be adjusted. After the visible light, infrared, and other images have been adjusted in size, shape, and resolution to the X-radiograph, they can be readily dropped into distinct layers o f the Photoshop docum ent for examination and comparison. Distortions can be carefully applied to images to improve the alignment of important features between layers. Such manual adjustments, how­ ever, may never result in exact alignments throughout the painting in all layers. It is typ­ ical for one-half to three-quarters of the fea­ tures of interest to exhibit good alignment or slight misalignment (fewer than 3 pixels) between various layers in the document. Features with misalignments between 5 and 10 pixels are found less often. In areas of particular interest, it is usually possible to adjust the document lay­ ers so that features do not fall into this upper range of error. Plate 26 illustrates the use of the transparen­ cy slider in the layers palette to compare (a) the visible-light image o f the Virgin in Jan Provoost’s Detroit Last Judgment with an IR R image (c) o f the same area.13 In the middle image (b), the transparency slider has been moved to assign 80 percent opacity to the IR R . This allows 20 percent of the visible-light image DIGITAL IMAGING AT THE STRAUS CENTER

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to be viewed simultaneously for comparison. The same features are available when zoomina: in to see details at high magnification. Anoth­ er type of adjustment can be made when merg­ ing two grayscale (noncolor) images such as the IR R and the X -radiograph, since the two together can result in a confusing image that is difficult to interpret. Colorizing the X-radio­ graph (d) and placing that version in a separate layer (e) o f the document allows a direct com­ parison when merged with the IR R (f).

Sp ecialized U N IX Software

Selected composite assembly projects in the Straus Center make use o f another software, VIPS, which deserves a brief mention here and which is documented elsewhere.14 The Sci­ entific D epartm ent at the National Gallery, London, has recently made this program avail­ able to other institutions. It runs under Sun Microsystems’ Solaris version o f the U N IX operating system. Among its many features, VIPS is designed to assemble multiple adjacent images, including IR R images, X-radiographs, and other technical images, collected from the vidicon to create high-resolution composites.15 After choosing points of correspondence in adjacent images, the software aligns these images and automatically equalizes value dif­ ferences between them. In the IR R mosaick­ ing process, VIPS shifts adjacent images vertically and horizontally; in X-radiographic composites, the program also rotates adjacent X-radiographs as necessary to achieve proper alignment. As with the assembly of infrared and X-radio­ graphic images in Photoshop, the adjustment of completed layers to create correspondence in the geometry between layers can be auto­ mated within the U N IX environment using VIPS.16 Since VIPS can resize and align layers that have been initially created as mosaics in other programs, including Photoshop, it offers a simpler, more automated means for creating layered documents.That is its appeal for some layering projects at the Straus Center. H ow ­ ever, given the facility with which layers can be viewed and manipulated in Photoshop, it is probable that images will continue to be brought back into that environment after cor­ 132

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rections are made using VIPS, and the Center will probably continue to work on the Mac­ intosh platform with Photoshop for most image-enhancement and document-viewing applications.

Ethical C oncerns in the Interpretation o f Im ages

Just as traditional photographs of artworks must be used with caution in making stylistic interpretations, digitized technical images should be viewed with at least a small mea­ sure o f skepticism. The complex conditions under which these images are acquired can lead to significant variations in the information they convey. IRRs are particularly problematic since tube sensitivity and filtration can give the impression that features that are actually pres­ ent in an underdrawing do not exist. The assembly process for both infrared and X-radiographic images can obscure and confuse the relationships between features if errors are made during the process. A little too much overlap between two adjacent images will obliterate information, sometimes w ithout leaving any evidence of the loss. Distortions used to cor­ rect problems in alignment may subtly alter the relationship between features, and local value changes made to even out the transition between images in a composite can alter the accuracy of tonal variations across the surface of the painting. W ell-intentioned corrections normally improve the readability of the composite, but they have the potential to confuse features that were not noticed at the time the assembly was made. Although there may b e a greater likeli­ hood of detrimental distortions when images are altered manually in Photoshop, automated corrections dictated by specialized assembly software can, in theory, alter images incorrect­ ly when using poorly acquired data. For these reasons, it is important to have some under­ standing of the procedures used in creating the variety o f technical images described in this paper; it is also critical to accurately record acquisition information for use in the future. The preservation of the individual raw infrared data files should be considered standard prac­ tice, since they can serve as a safeguard against

many possible sources of misinterpretation. An important feature of the VIPS application is that raw data files are preserved as components of each project and can easily be reviewed if nec­ essary. W ith X-radiographic and other filmgenerated images, it is likely that the original films can serve the same purpose. Outside the scope of this paper, but of crit­ ical importance, is the subject o f digital data preservation. The rapid changes in hardware,

software, and “standard” file formats are of great significance to the creation, use, and preserva­ tion o f technical images of artworks. Although certain strategies for data storage can be sim­ pler, faster, more efficient, and even more reli­ able and longer lived, none as they now exist can be considered long-term. Until a long-term strategy is found, the creators of significant col­ lections o f digital images must define clear administrative procedures to update storage solutions at appropriate intervals.

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NOTES

* The experiences and developments described in this paper are the result of working on projects with conservators and conservation interns at the Straus Center for Conservation, and in particular with R on Spronk, who collaborated on most of these innovations and provided several of the figures print­ ed here. Philip and Lynn Straus provided funding for the Center’s InfiraCAM-SWIR camera, and Catherine C. Lastavica made it possible to purchase the LightPhase camera back. The Straus Center’s work on these projects was made possible by the Harvard University Art Museums’ former director, Jim Cuno, who encouraged our experiments, and the assistance of the Museums’ computer support department. 1. Saunders and Cupitt 1993. 2. Snyder 1992. 3. van Asperen de Boer 1970. 4. The Amparo Corporation; the Metropolitan Museum of Art; and the National Gallery of Art, Washington, produced the Mosart program for MS-DOS-based desktop computers. The VASARI Project (Visual Arts System for the Archiving and Retrieval of Images: Birbeck College, London; The National Gallery, London; D oerner Institute, Munich; Laboratoire de Recherche des Musées de France, Paris) devel­ oped a mosaicking system as part of a larger project to record both color and infrared information from paintings. This sys­ tem is U N IX based and may be more widely used as muse­ um technical departments become adept at managing UNIX operating systems, http://www.laas.research.ec.org/esp-syn/ text/2649.html.

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5.This feature is available in Photoshop 3 and later versions. 6-Walmsley et al. 1994. 7. Newport tilt table #37S, and Oriel optical rail #11641. 8. The Zig-Align alignment device consists of four lights that are reflected between one mirror placed in the x-y plane of the easel and another placed on the lens mounting plate of the camera. When the mirrors are aligned, duplicate reflections of the lights appear to recede in the distance to a central point. Zig-Align, Inc., is in Menlo Park, Calif., www.zig-align.com. 9. Nathan Hazen is a retired engineer who worked for the Atmospheric Research Project, Harvard University. 10. Museum of Modern Art conservator James Coddington developed this means of examining paintings in the infrared by illuminating canvases from the reverse. 11. Walmsley et al. 1994. 12. Inframetrics, Inc., now named FLIR Systems, is locat­ ed in North Billerica, Massachusetts, www.flir.com. 13. For further information on this painting and the layer­ ing of technical documents, see Spronk 1998. 14. Saunders and Cupitt 1993, Billinge et al. 1993, Saunders and Cupitt 1995. 15. Billinge et al. 1993. 16. Saunders and Cupitt 1995.

W hat’s in a N am e? T h e Q u estion o f A ttrib ution in Early N etherlandish P ainting M aryan W ynn Ainsworth Metropolitan M useum o f A r t Although some self-styled Bernard Berensons dare to pronounce the authorship o f a painting without hesitation at a single glance from across a room, in recent years many have considered questions of attribution with a more sophisticated methodology. The latter group has recognized the contribution of information from the technical examination o f paintings and the results of art historians, conservators, and scientists engaged in collaborative studies. It is indeed appropriate that a discussion of this subject and publication o f the related papers have been organized by the Fogg Art Museum, for that institution was the cradle of much o f the activity that we associate with early efforts in connoisseurship. Toward the end of the nineteenth century, Bernard Beren­ son himself, as a young Harvard student, gained Isabella Stewart Gardners ear, her trust, and some would also say her pocketbook and helped her to form one o f the country’s pre­ eminent private art collections, subsequently opened to the public as the Isabella Stewart Gardner Museum. At the Fogg, Edward Forbes pioneered attempts to develop m odern con­ servation practices with a specific emphasis on the scientific analysis o f paintings. Forbes’s visionary approach led him in 1925 to encour­ age the curator Alan Burroughs to make X radiographs of the Fogg’s paintings collection and then to gather X-ray films o f compara­ tive works in the most im portant European galleries, thus creating the incomparable study collection at that museum. For the field of early Netherlandish painting, although James Weale succeeded in recon­ structing the lives o f Bruges painters in par­ ticular from archival sources and matching those documents with surviving paintings,1 the gen­ eral paucity of documentary evidence about artists and precise information concerning their

production encouraged earlier art historians to look for revelations in the works themselves. Between 1924 and 1937, Max J. Friedländer was the first to systematically catalogue the known Netherlandish paintings by artist and by group in Die altniederländische Malerei; this collection o f fourteen volumes was revised between 1967 and 1976 and is still indispens­ able for scholars today. But Friedländer left as uncharted territory the refinement o f these groups through a distinction between the pro­ duction of the master and that o f his workshop. He mostly ignored the study of versions and copies, as well as the division o f labor within an artist’s atelier— matters that, these days, have prompted a kind of renaissance in this field of research. Initially stimulated some years ago by the technical studies o f Paul Coremans at the Institut Royal du Patrimoine Artistique in Brus­ sels, a virtual explosion of recent investigations has taken place that relies not only on micro­ scope analysis and X-radiography but also on infrared reflectography and dendrochronology, to name just some o f the most frequently employed methods of examination. The launching o f new research projects is due in large part to the motivating force of J. R.J. van Asperen de Boer, who initiated stud­ ies in infrared reflectography in the late 1970s and who has been an unfailing proponent of interdisciplinary cooperation ever since. The publications o f the biennial colloquia in Louvain-la-Neuve and Bruges devoted to Le dessin sous-jacent dans la peinture under the direction o f R oger Van Schoute, Hélène Verougstraete, and the late Maurits Smeyers have provided a partial survey of developments in research about underdrawings over the past two decades. To this may be added the recent appearance o f museum collection catalogues and the corpus volumes of The Flemish Primi­ tives that increasingly rely on the full technical

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Fig. 1 a—c. Infrared reflectogram (IR R ), with two details, o f Gerard David, Virgin and Child with the Milk Soup, c. 1515. Oil on wood, 33 x 27.5 cm. Aurora Art Fund, New York. (IRR: Maryan W. Ainsworth, Metropolitan Museum o f Art, N ew York; digital composite: Alison Gilchrest)

examination of paintings in order to come to terms with questions o f attribution and dating. Initially, the technical study of paintings with­ out proper comparative material led to facile conclusions. For example, the lack o f under­ drawing in a painting was considered evidence 136

against an attribution to the purported artist; and the discovery of pouncing or tracing (as, for example, in the unquestionably autograph Aurora Trust version o f the Virgin and Child with the Milk Soup by Gerard David, plate 27 and fig. la—c) automatically signified a work­ shop product.2 O n the other hand, pentimen-

ATTRIBUTION IN EARLY NETHERLANDISH PAINTING

Fig. lc.

Fig. lb.

ti or compositional changes by the artist were thought to guarantee the product of a master rather than o f his assistant; furthermore, draw­ ings associated with any known paintings were most often categorized as copies after a given work, not studies made in preparation for it. Taking the last assumption into considera­ tion for a moment, we might briefly review some recent interpretations informed by the possibility of comparing the drawings with underdrawings in paintings.3 In one example, in a study of the details of the underdrawing in Hieronymus Bosch’s Death and the Miser (National Gallery o f Art, Washington) and its related drawing (Cabinet des Dessins, Louvre), it can be shown that the latter is a copy of the finished stage of the painting and was not made in preparation for it. Furthermore, scrutiny of the execution and handling of both drawing and underdrawing indicates that they cannot both be by the same hand.4 In another exam­ ple, Molly Faries has shown convincingly that certain drawings from the workshop ofjan van Scorel are directly related to an intermediary step of the creative process, a stage that estab­ lishes the system of fighting to be used in paint­ ings by the master.5 Advances in the methodology o f attribu­ tion have seemed to progress at a snail’s pace

because gathering the essential comparative material presents significant logistical, schedul­ ing, and financial constraints. But an irrepress­ ible enthusiasm for new discoveries has prevailed, and a considerable body of informa­ tion about artists’working procedures has been accumulated. Inevitably, various stages of recep­ tion and learning encountered in this type of research in the visual arts are routinely expe­ rienced in scientific investigation. Initially, infor­ mation is gathered and data are described in detail.Then comes that awkward stage of pre­ mature interpretations based on too few exam­ ples or the inadvertent selection of the wrong ones. The researcher often has a strong incli­ nation to name, identify, and categorize the object definitively in this phase, but in the next realizes that additional comparative material must be brought to bear on the question at hand and that an interdisciplinary approach has the potential of ensuring greater accuracy in interpretation. Recognizing the need for fuller information, newly formed interdisciplinary groups have begun to study the works attributed to early Netherlandish masters, and monographic stud­ ies are now based increasingly not only on the surface o f the painting but also on the creative process by which the end result was achieved. The works of a number of artists have bene­ fited from this kind o f scrutiny, producing a kind o f revised Friedländer (one wonders what he would have thought of these endeavors!) for artists such as R obert Campin (the Master of Flémalle), R ogier van der Weyden, Petrus Christus, Gerard David, Hans Mending, Jan van Scorel, Lucas van Leyden, and Hieronymus Bosch. And with these new efforts, the inevi­ table has occurred: The paintings attributed

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137

Fig. 2. R ogier van der Weyden, Christ Appearing to His Mother (detail from the Mary Altarpiece), c. 1435. Oil on oak, 71x 43 cm. Gemäldegalerie, SMPK, Berlin, 534A.

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Fig. 3. Copy after Rogier van der Weyden (possibly Juan de Flandes), Christ Appearing to His Mother (detail from the Mary Altarpiece), c. 1496. Oil on oak, 63.5 x 38.1 cm. The Metropolitan M useum o f Art, N ew York, 22.60.58.

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to these artists have turned out not to form the tidy individual groupings one might have hoped for. Although we may know much more about what these artists did and did not pro­ duce, this effort has generated entirely new questions that we could not have anticipated. In other words, it’s not just about attribution anymore. The net of inquiry has been cast much farther afield, and we now happily find our­ selves in territory that requires interdisciplinary approaches of all kinds: in various media, in dif­ ferent academic disciplines, and in the realm of scientific investigation. I would like to explore some of these avenues o f research that have opened up in the course of attempts to establish a name to precede the words mefecit on a large number of anonymous early Netherlandish paintings. WhenJ. R.J. van Asperen de Boerjeltje Dijkstra, and R oger Van Schoute examined by infrared reflectography the three panels of the Mary Altarpiece in the Berlin Gemäldegalerie (fig. 2) and the one in the Metropolitan Muse­ um of Art (fig. 3) that forms a triptych with two others in the Royal Chapel in Granada— at that time all attributed to Rogier van der Weyden— they reached a preliminary conclusion.6 Based on the characteristic underdrawing style known from authenticated works by Rogier, they pro­ posed (as was subsequently published7 by Rainald Grosshans, Berlin’s curator) that the Berlin version was the prototype and that the New York and Granada panels were copied from it. Supporting evidence was found in the under­ drawing o f the Berlin painting, which shows compositional changes from the layout stage to the final painted layers (e.g., in the hand of Christ and in the architecture of the landscape back­ ground), while the Metropolitan Museum underdrawing follows the finished state of the Berlin panel. Questions remained about the authorship of the underdrawing (as opposed to the painted layers); thus, further research was warranted before a final conclusion could be reached. Notwithstanding institutional pride and friendly rivalries in matters of this sort, it became a point of considerable interest to settle this issue of frequent art historical debate. At the Metropolitan Museum, we carried out infrared reflectography, X-radiography, and pig­ 140

ment analysis on the M ets painting, none of it contradicting the conclusions o f van Asperen de Boer, Dijkstra,Van Schoute, and Grosshans. Furthermore, the analysis o f the M et painting’s ground preparation (which turned out to be calcium sulfate, instead o f calcium carbonate) indicated that it was produced in southern Europe, most likely in Spain in front o f the Miraflores (now Berlin) original that served as its model. But it was the result of our invita­ tion to Peter Klein for the dendrochronology of the M ets Christ Appearing to His Mother that ultimately sealed the fate o f the painting. The earliest possible felling date of the panel used for the painting is 1482, eighteen years after R ogier’s death. Furthermore, given Klein’s sta­ tistical analysis, the panel was probably not used for the painting until the mid-1490s.8The deci­ sive information that closed the door on the possibility of the authorship o f Rogier van der Weyden, however, opened another. Klein’s lat­ er investigations confirmed that the M etro­ politan panel came from the same tree as panels used in the left and central portions of the Mary Altarpiece in the Royal Chapel of Granada.What was not anticipated was that certain other pan­ els also could be traced to the same tree.These are the ones used for the Beheading ofJohn the Baptist (Musée d’Art et d’Histoire, Geneva) and the Banquet of Herod (Museum Mayer van den Bergh, Antwerp), part o f a retable painted for the Cartuja o f Miraflores between 1496 and 1499 by Juan de Flandes, a Netherlandish artist who worked in Spain for Q ueen Isabella of Castile from 1496 until her death in 1504.9 Instead of a work by Rogier, could the Met­ ropolitan Museum own a faithful copy o f a R ogier van der Weyden painting by Juan de Flandes? Further attempts to ascertain the attri­ bution of this work now require study of the painting style and specific working techniques of Juan de Flandes. But our inquiries have also raised a more general question, one that is as intriguing as it is perplexing: How do we rec­ ognize an artist’s work when a unique person­ al style is suppressed in order to assimilate that o f another artist for the requirements of a par­ ticular commissioned work? We are on firm ground with relatively obvious cases in which the characteristic execution and handling of a known artist are not lost during the copying of a painting by another. The identification of

ATTRIBUTION IN EARLY NETHERLANDISH PAINTING

Rubens’s authorship in a copy ofMetsys’s Por­ trait of Paracelsus (Musées royaux des BeauxArts de Belgique, Brussels), or Jan Gossaert’s execution in his version of Jan van Eyck’s God the Father, the Virgin Mary, and Saint John (Pra­ do, Madrid) from the Ghent Altarpiece, is a fair­ ly straightforward affair. O ther cases prove to be more challenging, as when Petrus Christus diverged from his typical style in the finished painting (though not in the underdrawing) of the Los Angeles County M useum’s Portrait of a Man, an instance in which, I believe, Christus intentionally tried to mimic an Italian-style portrait, something akin to Antonello da Messi­ na’s production. And what would the docu­ mented three copies by Christus of the Cambrai Madonna have looked like? R ecently dis­ counted through dendrochronology is one of the Byzantine-style icons in Belgian collec­ tions, namely, that at the Brussels Musées roy­ aux des Beaux-Arts.10 But what about the case of the markedly sculptural and monumental Virgin and Child by Hans M emling in the National Gallery o f London (fig. 4)? Could this be the artist’s attempt to produce an Italianate Madonna to suit the taste o f one o f his many Italian clients?11 Is a patron’s request also the reason for a Davidian version o f a Hugo van der Goes Virgin and Child (National Gallery, London)?12 Now that we are more attuned to the par­ ticular requirements of the patron and the influ­ ence that the open art market wielded over the production of paintings in the fifteenth and six­ teenth centuries, some of the vagaries o f attri­ bution in cases where artists intentionally painted in styles other than their own may become clearer. In such instances, the revela­ tion of an artist’s working procedures, usually through technical investigations, more readily identifies his authorship than the completed painting. It would be a mistake, however, to automat­ ically assume that all of the preliminary stages uncovered by technical investigations belong to the self-same artist as the finished paintings. Thus we have learned from van Asperen de Boer’s research group on Rogiers paintings that in the celebrated Columba Altarpiece, the under­ drawing was made entirely by another hand, one that mapped out the composition and its

Fig. 4. Hans Memling, Virgin and Child, c. 1475. Oil on oak, 39.4 x 29.9 cm. National Gallery, London, NG709.

details before Rogier’s apparent encounter with Stefan Lochner’s Adoration of the Magi in Cologne.13 This experience apparently caused Rogier to reconsider certain details, such as the girl with the dove; the girl is in a fairly altered position and wears a different headdress than in the initial underdrawing. Sometimes it hap­ pens the other way around. In a lecture enti­ tled “Attributing the Layers o f Heemskerck’s Cologne Lamentation of Christ,” Molly Earies convincingly argued for the artistic presence of Jan van Scorel, M aerten van Heemskerck’s teacher, in the preliminary stages o f the paint­ ing.14This case o f “master beneath pupil,” not vice versa, demonstrates visual evidence of a documented relationship, even rivalry, between the two known painters. W hat about those cases in which we have only hearsay, m odern assumptions, and per­ ceived stylistic influences to rely upon when proposing the reconstruction of a master—pupil relationship? W ith no surviving documentary evidence, can we really establish that Hans Memling worked for a period of time as the assistant of R ogier van der Weyden? Recent-

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signals his liberation from his mentor and R ogier’s habitual workshop practices.16 Following this line of inquiry, we might endeavor to secure a link between artists and their purported masters by researching more closely the preliminary working stages of each. Such an exploration could help to explain the unknown origins and early training of a num­ ber of artists for whom this important infor­ m ation is lacking. It may also lead to new attributions of youthful works by these pupils. Initial attempts in this area have not always pro­ vided the anticipated outcome. Jan Piet Filedt Kok discovered, for example, that Lucas van Leyden’s early works do not appear to have any­ thing to show for the time he is reported by Karel van M ander17 to have spent under the tutelage o f Cornelis Engebrechtsz.18 Clearly, more research needs to be carried out in order to gain additional insight into the nature of the master—pupil relationship in fifteenth- and earlysixteenth-century Netherlandish painting and the possible variations in the nature of instruc­ tion in the Renaissance workshop.

Fig. 5. W orkshop o f R ogier van der Weyden (possibly Hans M em ling), The Annunciation, 1465—75. O il on wood, 186.1 X 114.9 cm .The Metropolitan Museum of Art, N ew York, 17.190.7.

ly, following upon Panofsky’s tentative sugges­ tion made in 1953, I presented an argument in favor of this affiliation in the example o f the M etropolitan M useum ’s The Annunciation (fig. 5), long attributed to a follower o f R o ­ gier van derWeyden.15The painting has a hint of Memling at an early stage o f development, that is, Memling attempting to emulate the style of Rogier. In the underdrawing, however, we come closer to identifying Memling’s hand as it is known in the underdrawings of his other early works, namely in the Triptych ofJan Crabbe, which itself shows a close stylistic link with the art of Rogier. Memling’s change from a metic­ ulous, controlled brush underdrawing in his early works to a broad, sketchy style in black chalk after c. 1465 when he moved to Bruges (as found in the Metropolitan Museum’s Mar­ riage of Saint Catherine, for example) perhaps 142

Matters o f training and influence are one thing; collaborative ventures are quite anoth­ er. Some of these instances during the fifteenth and sixteenth centuries in the N orth are well docum ented. The inscription on the Ghent Altarpiece tells o f the joint production by the brothers H ubert and Jan van Eyck (even though sorting out exactly who did what has remained one o f art history’s great enigmas). Later on, in the period o f developing special­ ization in early-sixteenth-century painting, a 1574 Escorial inventory reports that Joachim Patinir painted the landscape for which Q uin­ ten Metsys provided the figures in the Temp­ tation of Saint Anthony. W e know o f certain occasions, one in particular o f Albrecht C or­ nelis, w hen artists got into legal trouble for collaborations, or, more precisely, for subcon­ tracting work against the stipulations o f the legal agreement.19 O ther instances o f collab­ oration developed by accident rather than by plan, such as w hen the death o f an artist or the inability to complete a w ork required enlisting the services o f other artists. Familiar instances that come to mind are the two com­ pleted panels of four originally ordered of the Justice of Emperor Otto. One was carried out by

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Fig. 6. Gerard David and Workshop, Saint Nicholas (left), Virgin and Child with Saint Anne, and Saint Anthony of Padua (from the Saint Anne Altarpiece), c. 1500—6. Oil on oak, 236.1 x 97.5 cm. National Gallery o f Art, Washington, D.C., W idener Collection, 1942.9.17a—c.

Dirk Bouts and the other by his workshop. Bouts’s Martyrdom of Saint Hippolytus was a cooperative effort o f Dirk Bouts and an assis­ tant, who collaborated on the central and right w ing panels, and Hugo van der Goes, who painted the donors on the left wing.20 In the absence of documentary evidence, the identification o f jo in t authorship o f a given painting has traditionally been based on visu­ al analysis and on our sometimes rather arbi­ trary and subjective views of what an artist did and did not do. O ur elevated notion of a mas­ ter’s authorial presence and our traditional assignment of a kind of hierarchy to painted

portions o f a single panel or triptych needs réévaluation. Although numerous examples immediately come to mind o f altarpieces whose most hal­ lowed portion, the centerpiece, represents the work o f a principal artist and whose wings exemplify workshop participation, we ought not to become too complacent with this no­ tion. Quite to the contrary: An open-minded view about this m atter leads us to interest­ ing and probably more correct conclusions about the role o f the patron in commissions and the powerful influence exerted on artists and their production from time to time by eco-

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allowed for a reassessment of an attribution that has often been contested.The apparent wood­ en quality of the Virgin, Child, and Saint Anne in the triptych’s centerpiece provided ample reason for some to reject the attribution of the entire work, particularly when compared to the approximately contemporary (1506) Cervara Altarpiece, which is assigned irrefutably to Ge­ rard David (fig. 7).22 Further evidence sup­ porting this view came from the underdrawing in portions of the central panel, which showed a finicky, overly elaborate, relatively dry exe­ cution in brush for the draperies of the figures o f the Madonna, Child, and Saint Anne in a style not immediately identifiable as that of David (fig. 8). However, other parts of the cen­ tral panel, such as the putti, and the side pan­ els o f Saint Anthony o f Padua and Saint Nicholas exhibit a marvelously free prelimi­ nary sketch that is perfectly characteristic of Davids execution (fig. 9).

Fig. 7. Gerard David, Virgin and Child Enthroned (one of seven panels in the Cervara Altarpiece), 1506. Oil on oak, 153 X 89 cm. Palazzo Bianco, Genoa, 12.

nomic factors, which fostered mass-produced art for the open market or for export. Let us take for an example the Saint Anne Altarpiece in Washington’s National Gallery o f Art (fig. 6), whose predella panels are divided between Edinburgh and Toledo, O hio.21 Al­ though we do not know who commissioned one of the largest altarpieces to come out of Ger­ ard David’s atelier, its early provenance to Palma da Mallorca, an island off the eastern coast of Spain, may suggest that it was destined for a site there, perhaps for the Church of Saint Nicholas (the saint appears on the left side panel, and his story is featured in the predella). The 1991 cleaning and restoration o f the three large panels in the National Gallery have 144

In her examination o f the technique of the three paintings, Catherine Metzger conclud­ ed that the central panel was produced by a more labored and traditional method of work­ ing than the remainder o f the altarpiece.23 In other portions, a far more spontaneous execu­ tion, including modifications and corrections from the underdrawing and an abbreviated lay­ ering structure in paint, which achieved remarkable effects of refinement with an econ­ omy o f means, shows the self-assurance and authoritative handling of a master. As a result, technical evidence supports the attribution of the side panels and portions of the central pan­ el to David himself and the central panel fig­ ures of the Virgin, Child, and Saint Anne to a workshop assistant. This conclusion is contrary to what we might normally assume and requires further explana­ tion, at least some o f which can be made on the basis of a greater understanding of work­ shop procedures, and specifically those of Ge­ rard David’s own workshop. Centerpieces of triptychs or retables are often the standardized portions, repeating traditional themes for devo­ tional practice.They may even have been avail­ able in multiple examples in an artist’s shop for ready sale. The side panels, or the wings of an altarpiece, are the portions that may respond more often to the particular requirements of

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Fig. 9. IR R o f Gerard David, Virgin and Child Enthroned, detail (putto on the throne, upper left). (IR R : Maryan W. Ainsworth, Metropolitan Museum o f Art, New York; digital composite: Alison Gilchrest)

Anne was probably available as a workshop pat­ tern that could be transferred and executed in paint by an accomplished assistant. The side panels perhaps required new designs and cus­ tomized adjustments that could be more easi­ ly and quickly made by David himself.

Fig. 8. IR R o f Gerard David and Workshop, Virgin and Child with Saint Anne, detail. (IRR: Maryan W. Ainsworth, Metropolitan M useum o f Art, N ew York; digital com­ posite: Alison Gilchrest)

the patron, representing saints or scenes that relate specifically to the life or habitual devo­ tions of the client. In the Saint Anne Altarpiece, the group of the Virgin and Child and Saint

Such a formulation— a centerpiece relying on readily available workshop patterns, easily produced either by assistants or in a more rou­ tine and less spontaneous manner by the mas­ ter himself, w ith side panels indicating the “more creative” or inspired intervention of the master— is evident in other works attributed to David, especially those that were made for export or pieced together expediently for the open market. A case in point is the Philadel­ phia M useum o f A rt’s Lamentation and the Lehman Collection’s Passion Wings, which were reworked early on, perhaps in Gerard David’s own workshop, in order to fit together.24 N ow I come to a final issue in this brief review of the state of questions o f attribution

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in early Netherlandish painting. I refer to a mat­ ter that is highly problematic because of its subjective nature: the relative quality o f art produced in the workshop and the question of attribution. Lome Campbell has already drawn attention to this problem in works associated with Rogier van der Weyden, suggesting that a number of paintings destined for foreign loca­ tions were rather routinely of inferior quali­ ty.25 The num ber o f versions and copies o f standard themes associated with the workshops of particular artists readily shows the signs of mass production, that is, the transfer o f set pat­ terns through pouncing or tracing. I am think­ ing of the numerous replicas of the Holy Family originating from a design by Joos van Cleve, the Rest on the Flight into Egypt or the Virgin and Child with the Milk Soup associated with Gerard David, or Joachim Patinir’s signature landscapes. Rarely are these works signed, leav­ ing us to deal with the attribution question based on visual analysis and the results o f tech­ nical investigations. A signed and/or dated early Netherlandish painting is a rarity. However, just as technical examination has led us to positive attributions in works that are unsigned, conversely it may lead us now to doubt works that are signed. Lome Campbell recently touched on this mat­ ter when, following cleaning, restoration, and technical investigations at the National Gallery in London, he published a Virgin and Child long thought to be a late copy after Jan Gossaert as the original by Gossaert himself.26 M unich’s

146

signed and dated work “Joannes Malbodius pingebat 1527,” as well as a painting formerly in the Descamps Collection and a version in Vienna now pale by comparison and must be reassigned to workshop production. This reconsideration raises the problematic issue o f how early in the history of N orthern painting an artist’s name was employed more broadly to indicate the product from his work­ shop instead o f the singular painting by his hand. After all, selling works under his own name that were mainly produced by appren­ tices was a significant way in which a master could make a profit.The irony of the situation, therefore, is that just as our methods of detect­ ing authorship are becoming more sophisti­ cated and our judgments more reliable, we are thwarted by our increased awareness o f the changing status of the artist in the Renaissance as he moved toward becoming the “inventor” head of a workshop, where any product from his atelier might carry his name. In certain instances, the designation “group” may be the only reliable one. In broader terms, my sense o f the state of research into the question of attribution is that we are just beginning to probe all of the pos­ sible variations to be found in examples of ear­ ly Netherlandish painting. If we remain open to new interpretations from a wide sampling of the available interdisciplinary material, our research has the potential to yield remarkable new insights into this field of art history.

ATTRIBUTION IN EARLY NETHERLANDISH PAINTING

NOTES

1. van Biervliet 1991. 2. For a discussion of this problem, see Ainsworth 1998, 295—308.The most recent literature includes Buck 2000; Buck 2001a; Buck 2001b, passim; and Ainsworth 2003. 3. On this method, see Ainsworth 1989 and Ainsworth 1998, 7-55. 4. Filedt Kok 1973,151-52, n. 43.

10. Dendrochronology on the Brussels panel was carried out by Pascale Fraiture (report of 2 July 2002), who deter­ mined a terminus post quem of 1647 for the Brussels version. Information kindly conveyed by Helena Bussers (letter of 10 July 2002). For further, see Périer-dTeteren 1968. 11. See Campbell 1998, 359-61, who does not mention this possibility. 12. For a recent discussion of this painting, see ibid., 240-47.

5. Faries 1976,154-61.

13. Dijkstra 1985.

6. For a review of the published literature of this case, see the entry by M.W. Ainsworth in Ainsworth and Christiansen 1998,216-19. 7. Grosshans 1982. 8. Letter to M.W. Ainsworth o f 22 December 1992 on file in the Sherman Fairchild Paintings Conservation Department, Metropolitan Museum of Art. See Klein 1989 for a probable felling date of 1474 for the tree from which the panels of the Metropolitan Museum painting came. Klein revised this opinion (letter of 22 December 1992) when fur­ ther data became available from the dendrochronology of panels painted by Juan de Flandes; it was determined that these panels came from the same tree as those for the Metropolitan painting. The Juan de Flandes paintings formed part of an altarpiece o f Saint John the Baptist produced for the Cartuja of Miraflores between 1496 and 1499. See also Klein’s article in this publication. 9. Périer-dTeteren et al. 1993 and Borchert 2002,217, fig. 245; 266, cat. no. 116.

14. Faries 1995a. 15. Ainsworth 1994, 78-81, and cat. no. 10 in Ainsworth and Christiansen 1998, 112-14. 16. Ainsworth 1994, 81-84, and Galassi 1999. 17. van Mander 1994, 104—5. 18. Filedt Kok 1979, esp. 38—41. See also Faries 1993a. 19. See the entry by Dorien Tamis in Martens 1998,85—86. 20. Goetghebeur 2001. 21. See Ainsworth 1998,167-77. 22. Ibid., 177-201. 23. Metzger 1992, 52—63. 24. Ainsworth 1998,133-48. 25. Campbell 1994. 26. Campbell and Dunkerton 1996.

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G lossary W ritten, compiled, and edited by M olly Faries, Narayan Khandekar, Kate Olivier, and R on Spronk, with contributions by Teri Hensick, H enry Lie, Richard Mulholland, and Nico Van H out.

Italicized words within entries denote terms defined in this glossary. abrasion The area of a paint film that has been locally worn thin by friction or overcleaning. The top paint layers o f a painting often become abraded, but sometimes the entire paint film can be worn away, revealing the ground or support beneath. analytical microscope (fig. 1), see also cross section An optical instrument, also known as a research microscope, with high-quality optics that usu­ ally range in magnification from 50x to lOOOx. The microscope can be oriented for a variety of tasks, including reflected visible light, and ultra­ violet light microscopy, polarized light micro­ scopy, and microphotography. anatomy of a painting (fig. 2), see also exami­ nation routine In early Netherlandish painting, the discrete layered structure of support, ground, underdraw­ ing, and paint. The support was made from a wood panel (usually oak) or textile (see tiichlein), although the latter have not survived in great numbers. Panels were first covered w ith a w hitish ground, sometimes in several coatings, and generally preceded by impregnating the wood with a glue sizing. Fabric supports sometimes lacked the ground layer. In northern Europe, the ground was made from a mixture of chalk or calcium carbonate and glue (see also ground). The underdrawing was executed on the ground, either on top of or underneath a thin priming or isolation layer. This layer usually sealed off or protected the underlying ground layer from the upper layers and marked the division between the preparatory stages of a work and the execution in paint. Paint was applied over the underdrawing in one or more opaque layers or in superimposed layers of underpainting and glaze. Underpainting usually contained more lead white and was a tint of the color to come; frequently, it contained cheaper materials or more finely ground grains of pigment. R icher in medium and used to achieve a desired depth of tone, glaze was translucent and was often applied in multiple layers. Highlights, such as those executed in lead-tin yellow, and other types of linear detailing usually occurred in the last paint stages. The verso o f the panel was often painted as well, but usually in a slightly simpler layered structure. Any technical examination of early Netherlandish paintings must consider this specific lay­ ered structure. GLOSSARY

149

frame front varnish, glazes and highlights paint layers isolation layer underdraw ing ground layer paint layers, varnish reverse

barb

front varnish, . glazes and highlights / paint layers ■ isolation layer i ----- underdraw ing

unpainted edge panel support unpainted edge

ground layer : ----- paint layers, varnish reverse

Fig. 2. Schematic cross section o f the layered structure o f an early N etherlandish panel painting w ith engaged frame present (a), and w ith engaged frame removed (b). In this diagram, the isolation, or prim ing, layer is on top o f the underdraw ing, but in some cases, it can be underneath.

barb, or barbe (pi. 28, see also fig. 2) A raised lip consisting of ground and paint that accumulate at the edge of the painted surface where it meets the engaged frame. Over time, paint may crack at the juncture with the frame, so that the barb will appear as a rough, jagged edge. W hen the original engaged frame is lost— as in the case of the Fogg’s diptych of the Virgin and Child (left panel) and A Donor (Joos van der Burgh) and a Bishop Saint (right panel)— the support still exhibits a ridge of ground and paint (no. 2 in pi. 28) where the painted surface abuts an unpainted rim of wood where the panel was once covered by the frame (no. 1 in pi. 28).The presence of a barb on all four sides indicates that the painted surface has not been cut down from its original size. Throughout the fifteenth century and into the early sixteenth, panel makers typically manu­ factured panels with attached, or engaged, frames, which fully enclosed the panel. Sometimes, a small panel would be carved together with its frame from a single piece of wood. The frame in this case is called an integral frame. Each type of frame would have been in place when the ground layer and paint were applied to the panel, and the frame would also have been painted or gild­ ed. After the first quarter o f the sixteenth century, most panels were painted before a frame was attached. Barbs do not exist on these later panels because the ground and paint layers extend to the very edges of the support. Since a barb contains a dense concentration o f material, it often shows up as an opaque, whitish strip in an X-radiograph. 150

GLOSSARY

binding medium, see medium binocular microscopy, see stereomicroscopy blanching A whitish residue of partially removed varnish on the paint surface. blind cleavage An area of paint, and possibly ground, that has started to detach from the support but has not cracked or become significantly raised.The presence of blind cleavage is often difficult to detect and can sometimes be determined only by applying light pressure to a painting’s surface where detachment from the support or ground is suspected by a conservator. Blind cleavage is virtually impossible to detect under infrared light or with X-radiography. blooming A cloudy, whitish or bluish transformation of a varnish, wax, or paint layer, generally caused by the exposure of varnish or wax to moisture. Blooming can also result from a layer of varnish or paint developing minute, light-diffusing cracks. bole, see gilding color notations Marks, letters, abbreviations, and words referring to colors in drawings and underdrawings. The use of notations to lay out color was recommended as early as the late twelfth century byTheophilus as part of the making of stained glass, and the practice has continued for centuries. In early Nether­ landish painting, color notations usually refer to a pure color, although references to mixtures also appear. Notations have been interpreted variously as instructions for assistants and as indi­ cations of the amount o f a pigment to be ground for paint. See further the essay by Molly Faries and her fig. 7. compositional change Alterations— modifications, corrections, repositioning, enlargements, reductions, omissions, or additions— introduced by the artist that occur during the underdrawing and/or painting process. They may be made for aesthetic or iconographie reasons, at the artist’s initiative or at the behest of the patron. “Additions” can refer to those made either by the original artist or by another hand at a later date. Compositional changes are routinely disclosed by technical methods of investiga­ tion, and it is therefore incorrect to refer to such changes as pentimenti (i.e., unintended revela­ tions that become visible to the unaided eye). By combining different methods of investigation, particularly infrared reflectography, X-radiography, and cross sections, compositional changes can often be described quite accurately and locat­ ed within the sequence of the painting process. Changes or stages in the underdrawing will register in infrared reflectography, while X-radiography reveals alterations in subsequent stages in paint. If changes occur after the completion of the underdrawing and at the beginning o f the paint stage, forms in the X-ray will diverge from forms in the underdrawing. Changes made in an inter­ mediate painting stage will correspond to forms in X-radiography but will not be visible on the surface. For instance, forms indicated in the underdrawing may be taken to a paint stage during an application of paint, or by delimitation of the form with surrounding paint, and may then be changed further or painted out in subsequent paint layers. The essay in this volume by Gianfran­ co Pocobene and R on Spronk provides a good example of how compositional change can be clarified and ascribed to various painting layers: their figs. 7a and 7b compare infrared and X-ray images of the same detail. Compositional changes can also be important clues in assessing whether an artwork is an orig­ inal composition or a copy. It is often thought that the closer a painting is to being a copy, the GLOSSARY

151

fewer the compositional changes in the painting process. Some small adjustments, however, have been discovered in sixteenth-century workshop replicas. See further the essay by Molly Faries. computer layering, see layering copying routines Methods of transfer to create a duplicate or multiples of an original composition. Most copy­ ing techniques, such as pouncing, squaring, and tracing, were known before the period o f early Netherlandish painting. Although it is assumed that pouncing was employed in the making of compositional replicas by the mid-fifteenth century in the Netherlands, most overt examples o f pouncing date from slightly later and continued into the sixteenth century. The first dated example of squaring in a Netherlandish panel painting was revealed by infrared reflectography in Jan van Scorel’s Obervellach Altarpiece (1519). Artists may have previously known about squaring, however, and if a proportional relationship exists between the measurements of two or more related compositions, this technique may have been employed. As suggested in the essay by Molly Faries, tracing may have come into more frequent use in the sixteenth century. All these methods rely on a compositional model and therefore imply that a sheet o f paper, or similar material, is used as a pattern. Although these routines are used to make “copies” in a strict sense, they also have other purposes.When used for compositional transfer, these techniques can facilitate the painting of an “original” by a master painter or the production of a series of “authen­ tic” shop replicas, where in some cases there is no true original. cracks, see also craquelure Breaks in a ground, paint film, or varnish. Cracks can be caused by drying, aging, mechanical action, or a combination of these factors. Drying cracks can occur when volatile paint components evaporate, which may cause a ground or paint layer to shrink and split. Drying cracks can be caused by siccatives or dryers in the paint or by painting “lean over fat,” that is, applying paint that is relatively poor in medium over lay­ ers that are rich in medium. These cracks may also be caused by painting over an earlier layer that is not fully dried or by painting on an overly smooth ground. Drying cracks are located in the upper paint layer(s) only and do not necessarily correspond to cracks in the ground. Age cracks— which are often difficult to distinguish from drying cracks— can result from dimen­ sional changes in the support over time, placing stress on any or all layers, which lose elasticity upon aging. Different supports typically show different crack patterns. Age cracks on panel paint­ ings will often reflect the grain o f the support. Mechanical cracks can result from external causes, such as blows or scratches. cradle, cradling A gridlike construction o f wood attached to the back o f a panel support to prevent it from warping due to changes in relative humidity. Cradling began to be used in the mid-eighteenth century and became popular in the nineteenth, often being performed as a preventive treatment. Before a cradle was applied, the reverse of a panel was usually planed down to provide a level surface for the cradle’s attachment and to minimize the panel’s response to environmental fluc­ tuations. The bars o f the cradle that run parallel with the wood grain were glued to the panel and contained slots for the cross bars; these cross bars— running perpendicular to the grain— were meant to move freely within the slots to keep the panel flat. For an illustration of a cradle, see fig. 8 in the essay by Gianfranco Pocobene and R o n Spronk. Only recently have the material properties o f wood panels been understood more fully, and cradling is no longer a generally accepted treatment. Also, when they are very thin, wood pan­ els remain highly responsive (perhaps even more responsive) to changes in relative humidity. Slid­ ing members of the cradle typically lock as the wood swells, culminating in warping of the thinned 152

GLOSSARY

panel. The cradle’s restraint of the painting can result in severe structural problems, such as the splitting of the panel and flaking of the ground and paint layers. Extreme thinning often requires an auxiliary support, which can hamper both dendrochronology and X-radiography; a cradle can be particularly interferring. craquelure, see also cracks The pattern o f visible cracks in the paint layers or varnish. Since age cracks often reflect the grain of the support, different supports typically exhibit different craquelure. To blend retouch­ ing with original paint, restorers often imitate original crackle patterns and create artificial cracks. cross section, see also pigments (for examples of cross sections, see pis. 3, 22—25) A minute chip of paint embedded in a solidified plastic medium, which is ground flat and then polished to reveal the stratigraphical structure o f a painting. Ideally, a cross section includes all layers: support, ground, paint, and varnish. A cross section can be analyzed with a variety of instruments including reflected-light microscopy (using an analytical microscope), ultraviolet fluorescence, and X-ray analysis in a scanning electron micro­ scope (SEM) via energy-dispersive X-ray analysis (EDX) or energy-dispersive spectroscopy (EDS) or an electron beam microprobe. In reflected-light microscopy, one can determine the sequence of layers, their relative thicknesses, and their compositions— that is, the mixture of materials com­ posing each layer as well as the color and size of the pigment particles. The identity of the pig­ ments and other materials is only provisional in microscopy and requires more sophisticated laboratory analysis via such instruments as electron microscopes or electron beam microprobes. A thin section is a cross section thin enough for light to pass through it. The section can be viewed by transmitted or polarizing light and the color, size, and angularity of particles studied. Like the cross section, the thin section can be further analyzed by scanning electron microscope or electron beam microprobe. cupping An island of lifting paint (and sometimes ground) with the edges raised toward each other, form­ ing a cuplike shape. It is often necessary to secure cupping paint in order to avoid flaking. dead color, see also undermodeling, underpainting Underpainting executed in subdued or muted tones or colors. The first known usage in En­ glish of the term “dead color” dates from the notes of Melchior Salabosch, a portraitist active in England at the end of the sixteenth century. He used the word to describe the greenish under­ layer of skin tone, the “terra verde” or “verdaccio” in Italian painting. The term had probably been introduced to England by painters from the Netherlands: the word “doodverf” had appeared in fifteenth-century Netherlandish literature to describe palish tones and the color of a corpse and also appears in artists’ inventories and other documents describing unfinished paintings.The term soon described all paint layers between the ground and the surface layers. W ithin the paintlayer structure, dead color has organizational, technical, and optical functions. In modern Dutch, the verb “doodverven” still means “to predestine.” The method of painting in a single, direct layer, without dead color, is called “alla prima,” or in Dutch, “ten eersten opdoen” (from Karel van Mander’s Schilder-boeck [1603—4]). delimitation, see also compositional change A practice whereby certain details or major design areas are left open or in reserve in a paint layer, to be filled in later. Delimitations can be revealed both by infrared reflectography (IRR) and X-radiography. IR R can disclose delimitation if the form has been surrounded by a dark paint that remains partially opaque in infrared, while X-radiography can reveal a delimitation sur­ rounded by a dense pigment, in many cases containing lead white. For example, green trees in a painting’s background could be delimited, following the underdrawing, by the light blue paint of the sky; in an X-ray, the forms o f the trees would be dark, corresponding to the spaces left open GLOSSARY

153

to be filled in with green, X-ray transparent paint, and the sky would be light, showing the paint strokes establishing the outlines of the shapes of the trees. Typically, most figurative painters would work (and still do today) in this “back to front” man­ ner. The correlation of the underdrawing with areas of delimitation can provide important insights into the genesis of a composition. For an illustration o f a delimited feature, see fig. 7b in the essay by Gianfranco Pocobene and R o n Spronk, in which the X-radiograph shows that the hand of the Christ child was left in reserve in the Virgin’s robe. dendrochronology A dating method for trees and wooden artifacts such as panel supports. To derive dates, the growth-ring pattern on the end grain o f a plank is measured and compared with the growth curve o f a master chronology for a particular wood species from a particular geographic locale. This comparison often yields an earliest possible felling date for the tree and thus a terminus post quem date for the production of the painting. Statistical values are then applied, using estimates for sapwood growth and seasoning, to further estimate the most probable felling date of the tree and the date after which the wood would have been available for use. Dendrochronology is an especially useful component in the technical study of Netherlandish painting and can provide dating estimates for about 85 percent o f existing works painted on pan­ els. This is because almost all Netherlandish paintings were executed on oak that was imported from the same climatic region in the Baltic. Beech (and sometimes spruce) can also be dated dendrochronologically, and some local chronologies exist for fir and pine. In general, poplar cannot be dated. See also the article by Peter Klein. digital infrared reflectogram composite, see infrared reflectography dowel, see join/joining drawing, see also underdrawing W ithin the early Netherlandish tradition are found numerous extant drawings, although the majority that survive are copy drawings, rather than those preparatory to the painting process. The underdrawing is only one type of preparatory sketch. Others would include portrait sketch­ es; studies o f details, landscape motifs, and patterns; and partial or whole compositions. Research has shown that the technique and medium of drawings and underdrawings vary in relation to their function and that drawings and underdrawings are sometimes interrelated. See further the essay by Molly Faries. dyestuff A dissolved material that colors by staining. Unlike pigments, dyestuffs contain no particles. Most dyes are organic compounds and can be derived from natural sources (e.g., madder) or are synthesized (e.g., phthalocyanine blue). If the dye is precipitated onto a transparent carrier, it becomes a lake pigment. egg tempera Paint medium o f water and egg (generally only the yolk), into which dry pigments are mixed. W hen dry, egg tempera forms a hard and durable paint film. Its rapid rate o f drying prevents the blending of colors and requires that gradations of tone be produced by layering, hatching, and cross-hatching with a brush. Although usually associated with Italian painting, egg tempera is also known to have been used in Netherlandish painting. The exact manner in which oil and egg tempera paints were used together has been a hotly debated issue. It is now believed that these combinations can occur in areas side by side on a painting as well as in lower or upper layers o f paint. Formerly, it was thought that the use o f an egg—oil mixture as medium was typically limited to lead-tin yellow paint, which was often used 154

GLOSSARY

to depict small highlights and thus had to dry quickly without flowing (see further under emul­ sion). See also the articles by Molly Faries, Melanie Gifford, and R on Spronk. electron beam microprobe An instrument that can precisely analyze and quantify the composition of a pigment by mea­ suring X-ray fluorescence using a wavelength-dispersive detector. Organic materials from a sample are damaged during this analysis while inorganic materials survive intact. Electron probe microanalysis (EPMA) utilizes a wavelength- and an energy-dispersive analyz­ er. Wavelength-dispersive spectroscopy is used in quantitative analyses (determining the amount o f components of a sample), and the energy-dispersive analyzer is used in qualitative analyses (determining the presence or absence of chemical elements). Quantitative analyses may be car­ ried out with EPMA, using an attached computer. electromagnetic spectrum (fig. 3) A continuous series of radiation, defined by wavelength. Visible light is a form of electromag­ netic radiation; only a narrow band o f the electromagnetic spectrum— from approximately 400 (the color violet) to 700 nanometers (the color red)— is visible to the human eye. Forms of electromagnetic radiation are distinguished by their wavelengths, which vary from kilometerslong radio waves to ultrashort gamma rays. From the longest (with the least energy) to the shortest (the most energy), the electromagnetic spectrum is made up of: radio waves, microwaves, infrared light, visible light, ultraviolet light, X-rays, and gamma rays. Infrared light, ultraviolet light, and X-rays— forms o f electromagnetic radiation invisible to the human eye— are used to exam­ ine paintings, but every technical examination should start with a thorough study of the paint­ ing in visible light.

Fig. 3 .T h e electrom agnetic spectrum (1 nanom eter = 10 9 meters, or 1 m eter = 1 billion nanometers).

emulsion, see also medium A medium made of two immiscible components (such as egg mixed in oil) that form a solid film upon drying. energy-dispersive X-ray analysis (EDX), or energy-dispersive spectroscopy (EDS), see X-ray fluorescence engagedframe, see barb examination routine A thorough examination of a painting, beginning with different forms o f surface examina­ tion; proceeding to methods that penetrate into its paint-layer structure; and concluding with point examination, or the taking o f paint samples (a destructive technique). During the initial exami­ nation, the surface is assessed by eye and magnifying glass, the edges and reverse are examined, the parts composing the support are measured, and the entire paint surface is scrutinized by stereomicroscopy. The penetrating methods, infrared reflectography and X-radiography, complement each other: IR R images the compositional layout in the underdrawing, and X-radiography reveals GLOSSARY

155

the first applications of paint in relation to the layout. IR R demands the active presence of researchers because the painting is scanned in small increments. In principle, researchers should only undertake sampling when the results from other methods have been collated and the rea­ sons for removing samples have been formulated clearly. Experience has shown that IR R works well as a lead-in method. It yields information about condition, color, and technique related to the paint surface that can be studied further with the stereomicroscope, and can reveal aspects of the painting process that can be studied further by X-radiography and cross section. flaking The loss of sections ofground and/ or paint caused by the lifting and detachment of one or more layers of a painting. Flaking can be caused by humidity fluctuations, water damage, or the appli­ cation or composition of the paint or ground layer. It usually follows the existing crack pattern. focal plane array A two-dimensional grid of detectors on charge-coupled devices (CCDs) that allows images to be captured with a single snap of the camera shutter. Focal plane arrays are used in most dig­ ital still cameras and differ from one-dimensional linear array systems, which must scan across the focal plane over a period of seconds or even minutes to produce images. Fourier transform-infrared (FT-IR) spectroscopy (figs. 4, 5) An instrumental technique used to determine the identity of a wide variety of materials, includ­ ing pigments and binding media. Infrared light is either passed through a sample or reflected from its surface. Some of the light is absorbed by the chemical bonds, causing them to vibrate, stretch, and rotate. These movements are measured in wave numbers to give an infrared spectrum of absorbance and transmittance. The distribution of the wave numbers is particular to the chemi­ cal bonds under scrutiny, leading to the identification o f the compounds in the sample. Fourier transform mathematics allows for a weak signal from a small sample to be collected hundreds of times to build up an interpretable spectrum. Several digital libraries of FT-IR spectra are now available, and comparison of test results with reference spectra or correlation tables for known types of absorption bands can lead to the identification of the material. FT-IR spectroscopy requires a sample from the object, but the sample can often be used again for other analyses.

Fig. 4.T he FT-IR bench at the Straus C enter for C on­ servation, Harvard University A rt M useums, w ith the m icroscope at right and the liquid nitrogen tank for cooling the detector at left.

156

GLOSSARY

Fig. 5.Two Fourier transform -infrared (FT-IR) spec­ tra o f absorbance vs. wave num ber from a paint sam­ ple (a) and a reference m aterial (b). F rom this com parison, it was possible to determ in e th at the m edium in the sample is linseed oil.

gas-liquid chromatography (GLC or GC) (fig. 6) A laboratory technique in which complex mixtures o f organic materials in the mobile phase are separated according to functionality and size by passing through a silica-based mate­ rial in the stationary phase. The separation occurs because of the differing attractions of the substances being analyzed. In GLC, the sam­ ple is volatilized and passes through a narrow bore column lined with the stationary phase, which separates the compounds. A mass spec­ trometer can detect and identify the different components as they emerge from the end of the column. This is called gas-liquid chro­ matography mass spectroscopy (GC-MS). GLC is particularly useful in identifying dif­ ferent types of binding media, resins, and var­ nishes. The sample is destroyed during the procedure. gilding (pi. 29a,b), see also press brocade The process by which gold or silver leaf is Fig. 6 .T he gas-liquid chrom atographer at the Straus applied to a surface. Gilding can be done direct­ C enter for Conservation. ly onto the ground, but sometimes a bole (a mixture of reddish-brown or yellowish clay and animal glue or glair [egg white]) is used as a cushioning and colored underlayer. O ther finely ground pigments have also been used for this purpose. The glue or glair makes the bole adhere well to the porous ground layer. Since the ground or the bole is moistened w ith water or size before adhering the leaf, the process is sometimes called water gilding. Finally, the gilding is burnished so that it bonds with the ground or bole and forms a gleaming surface, usually for the background and other large portions o f a painting. Oil mordants are also used to adhere leaf, as has been found in German painting, and in those cases, the areas are not burnished. Water gilding is applied before the paint layer. In contrast, a com m on form o f mordant gilding is executed on top o f finished paint or on top o f water gilding (see pi. 29a,b). M or­ dant gilding is often used as a finishing touch for details in relief such as the decorative borders of robes or illusionistic rays o f light. A thickened oil mordant, often mixed w ith yel­ lowish pigments and other materials w ith good drying properties, is used as an adhesive.To create mordant gilding, the mordant is painted on in thin lines and the leaf applied while the adhesive is still tacky. Any surplus leaf would be brushed away, leaving a thin golden strand standing out in relief. M ordant gilding is often abraded, exposing the mordant under­ neath. glaze A thin, relatively transparent film of medium-rich, paint, usually applied over a more opaque underlayer. Sometimes glazes are built up in multiple layers to achieve deeper tones. Most glazes in early Netherlandish painting have been found to contain oil; for red and green glazes, sometimes resin was added. Glazes are especially vulnerable to strong cleaning sol­ vents. See plate 20 for an illustration o f a glaze.

GLOSSARY

157

glue, glue distemper In addition to its use as an adhesive, an animal substance used as a medium for paint. “Distemper,” as it is also called, was made by boiling the skin and bones o f an animal (usually a rabbit) and sometimes only from parchment cHppings. Glue is the medium generally found on tüchlein paint­ ings. It was also frequently used in egg tempera paintings for certain blues (lapis lazuli and azurite) that required a stronger adhesive than egg to hold the coarser pigment particles to the surface. ground The preparation layer between the support and the paint layers. Its main purpose is to provide a suitable surface for painting or drawing, with optimal texture, color, and absorbency. The ground is often applied in several layers and then scraped and/or polished to a smooth surface. Cross sections rarely include the entire ground layer, and determining average thicknesses is thus difficult. However, grounds in northern painting are typically thinner than gesso grounds in Italian painting, and grounds in early Netherlandish painting are thought to become even thin­ ner over the course of the fifteenth and early sixteenth century. Unlike panel supports and pigments, the ground layer was produced solely of local materials. Thus, in northern countries, grounds were traditionally made from mixtures of natural chalk (calcium carbonate) and animal glue, while in Italy and Spain, the inert material was gypsum (nat­ ural hydrated calcium sulfate). Researchers have also found coccoliths, the remains of tiny marine organisms, in some of the grounds of early Netherlandish panels. Thus, the chemical composi­ tion of the ground can also be a useful indicator o f a paintings origin and date. For examples of such examinations, see the essay by Molly Faries. growth ring, see also dendrochronology The layer of wood produced every year by the cambium. Innermost rings are oldest, and out­ ermost ones are youngest. The date o f the last extant growth ring on a painting panel is the only date that may be deter­ mined with certainty; it is impossible to know how many sapwood rings were trimmed and, when there is no longer any sapwood present, whether any heartwood rings were removed. Neverthe­ less, the number of growth rings provides a start to estimate the date of a painting. Master chronologies of continuous date sequences have been derived for various woods. The chronology for oak from the Baltic region, which was commonly used in Netherlandish paint­ ings, has been documented for 990 years. See further the article by Peter Klein. heartwood, see also sapwood, growth ring The central wood of a tree. imaging SIMS (secondary ion mass spectrometry) A fairly new, nondestructive, analytical technique that measures the mass spectrum of a cross section after ionization of atoms and molecules with an ion beam that releases secondary ions. The technique has the advantage of high resolution: a spatial resolution of 0.1 pm has been report­ ed. It also has the ability to distinguish both organic and inorganic materials. To date, imaging SIMS has often been used in combination w ith FT-IR spectroscopy to study the formation o f lead soaps in oil paint during the aging process and the discoloration of the blue pigment smalt. See further the essay by Molly Faries. impasto Thickly applied, or “impasted,” paint. imprimatura, see also priming A final layer applied to the ground that changes its color. The term obviously derives from Ital­ ian painting treatises, such as that by Vasari where “imprimatura” is described as an earth-colored 158

GLOSSARY

layer containing driers such as lead white and clay, applied on top o f the gesso ground and under the underdrawing. Sometimes the term is used in a more general sense to refer to any kind of priming. This can be misleading, for it fails to specify the particular characteristics o f priming layers in early Netherlandish painting and to distinguish them sufficiently from painting prac­ tices that postdate Vasari. infrared Invisible electromagnetic radiation with a wavelength longer than the red portion of visible light (circa 700 nanometers) and shorter than radio waves. For the examination of paintings, only radi­ ation from the near-infrared (NIR) region (700—2,500 nanometers), which is unrelated to heat, is used. infrared composites, see infrared reflectography infraredfalse-color (IRFC) An image in which color is produced differently than in a conventional color image in order to discern the response o f pigments or inks in the near-infrared (NIR). False-color images can be produced by blocking blue light with a filter and using film sensitive to both visible light and the near-infrared. Today’s charge-coupled device (CCD) cameras can also be used to accomplish the same purpose, by dropping the blue channel and recomposing an R G B image with the remaining color channels and the N IR image. Iron gall inks, which become almost totally transparent in the near-infrared, can be easily visualized in IRFC. The technique has also been used to differentiate pigments in manuscripts, although it appears to be most reliable for blues (ultramarine blue becomes reddish in IRFC). infrared (IR) photography Photographic technique that can partially reveal the components of layers below a painting’s surface. Infrared photography requires a special film and lens filter (to filter out the visible light) but can be done with a conventional camera and illumination. IR films are sensitive up to around 900 nanometers, or just beyond the visible range in the electromagnetic spectrum. More recently, digital cameras have become available that are also more sensitive in the infrared region (up to approximately 1,000 or 1,100 nanometers; see the article by Henry Lie). The use of IR photography in conservation began in the 1930s, mainly to study the condi­ tion of paintings and sometimes to help read signatures. Since 1941 (when Sheldon Keck pub­ lished his article “A Use of Infra-red Photography in the Study of Technique” in Technical Studies in the Field of the Fine Arts), but mainly in the 1950s and 1960s, IR photography has been used to reveal underdrawings, for which it is only partially successful. At this wavelength, pinkish skin tones, whites, browns, and reds are penetrated to a certain extent, but in general, no underdraw­ ing can be revealed underneath blues and greens. IR photography can, however, be used to reveal underdrawing materials that become fully transparent in infrared reflectography, such as iron gall ink. The technique also allows for creating photomacrographs in the infrared to study underdraw­ ing materials. infrared reflectogram, see also infrared reflectography The image produced by infrared reflectography on a TV monitor or computer screen. The term is also used to refer to the document itself, recorded photographically or digitally. infrared reflectography (IRR) (fig.l in the essay by J. R . J. van Asperen de Boer; figs. 6, 8—10 in the essay by Henry Lie) An imaging technique developed in the late 1960s and 1970s to overcome the limitations of infrared photography in detecting underdrawings. IR R uses an analog or digital video camera equipped with an infrared imaging device that is usually sensitive up to approximately 2,000 nanometers (compared with an IR photography sensitivity limit of 900 nanometers). At these wavelengths, a paint surface can be penetrated to a much greater extent than with IR photography, and under­ GLOSSARY

159

drawings can be revealed beneath most blues and greens. Imaging devices equipped with a plat­ inum silicide (PtSi) focal plane array are sensitive up to 5,000 nanometers, but typically the region o f 1,500—1,900 or 1,500—2,500 nanometers is used. To obtain infrared reflectograms, a light source containing some infrared content is directed at the painting. The white ground wih reflect this radiation while dark materials, most of which con­ tain carbon, wih absorb it and appear dark. The detector registers the contrast between areas of absorbed and reflected infrared radiation and converts this signal into a visible image on a video monitor or computer screen. This image, called a reflectogram, provides a real-time image that can be photographed or captured digitally. True blacks in the paint layers also absorb infrared radiation and remain opaque in IR R . Metalpoint underdrawing, which does not contain car­ bon, is known to register in IR R as well. Because of the relatively low resolution of most IR R systems, many close-up images are nec­ essary to document an underdrawing. Reflectograms used to be assembled by cutting and past­ ing individually photographed images into an infrared reflectogram assembly but nowadays are more typically assembled on the computer (see also the articles by Molly Faries, J. R. J. van Asperen de Boer, and Henry Lie).The latter are termed “infrared reflectogram digital composites.” Infrared studies have helped in issues o f attribution, to distinguish original from copy and to clarify workshop practices. See further the essay by Molly Faries in this publication. infrared vidicon, see also infrared reflectography (see fig. 6 in the essay by Henry Lie) A TV tube, outfitted with an infrared-sensitive lead sulfide coating and sensitive in the infrared range. inpainting The painting done by a conservator or restorer in areas o f surface loss. Unlike retouching, which often covers areas of original paint, the term “inpainting” implies that the paint is applied to the area o f loss only, with no overpainting of the original paint surface. Conservators employ different methods of inpainting depending on the type and size of object being worked on and the level of visible rework deemed appropriate. The reversibility o f the inpainting— i.e., the ease with which it can be removed— is also an important consideration. isolation layer, see also priming A priming layer that seals off the ground from the paint. join/joining Methods used to attach wooden planks to one another. Since the oak boards available in the fifteenth century were rarely more than 30 cm wide, large panels had to be constructed by join­ ing planks together. Planks were usually simply butt joined, that is, abutted to each other and glued; but they could also have lip joins or tongue-and-groove joins. Devices such as inlaid butterfly cleats, wooden dowels, and pegged splines (or keys) were used as much for aligning planks as for joining. Since they are inlaid, butterfly cleats can be seen on the panel surface (those on panel reverses are often restorations).Wooden dowels and splines are inserted into holes or slots drilled into a plank’s interior edge, and as a result, are usually only detected in X-radiographs. Dowels or splines may become exposed when a panel is thinned when attaching a cradle. O n the other hand, pegs securing a spline into adjacent planks wih be visible on the surface. Pegged splines do not seem to occur very frequently, but they character­ ize the panels of Hugo van der Goes and Jean Behegambe. For an ihustration of these and other types o f joins, see Verougstraete-Marcq andVan Schoute 1989, fig. 7. lake, see also pigments A pigment formed by precipitating an organic dye onto a stable transparent inorganic base or substrate such as aluminium hydrate (alum) or calcium sulfate. Lake pigments often have similar 160

GLOSSARY

refractive indices to paint media and, as such, appear transparent. Lake pigments are often found in glazes. The process of forming the pigment is known as “laking.” layering The compositing of multiple technical images, one on top o f another, in a digital document. Using this technique, infrared reflectograms, X-radiographs, visible-light images, and other images of a painting can be easily compared by flipping from one image to another. Layers can also be assigned partial transparency to permit viewing of more than one layer at once (see the article by Henry Lie and his plate 26). macrophotograph, see photomacrograph marks (fig. 7) Impressions made by tools; lines; m ono­ grams; and forms gouged, stamped, or brand­ ed onto sculpture, frames, and the flat front and reverse surfaces of panels. If not sawn or planed down, panel reverses often show the marks o f w oodw orking tools. Linear forms that do not cross from one plank to another, similar to those thought to be “house marks,” are sometimes gouged into the wood. These have been interpreted variously as lumberjack marks, marks associated w ith the wood trade, or marks o f a carpenter or panel maker. Their Fig. 7. A brand mark with double hands o f the St. Luke similarity to stonecutters’ marks has been guild in A ntw erp from the frame o f Joos van Cleve’s rightly noted. Saint Reinhold Altarpiece (M uzeum Narodowe, Warsaw, Guild marks o f the southern Netherlandish 185.007).T he scale is in centimeters. cities o f Antwerp, Brussels, and Mechlin fre­ quently appear as brands. Perhaps the best known are the compass and carpenter’s plane of the Brussels shrine workers’ guild and the double hands and castle (burchi) of the Antwerp guild o f St. Luke. In Antwerp, the marks are an assurance o f quality for the benefit o f the client: the hands indicate the guild’s approval o f the quality o f the wood, and the castle indi­ cates approval o f the polychromy. Such practices are described in guild records as early as 1454 (Brussels) and 1470—72 (Antwerp). Later in Antwerp in 1617, the use o f panel makers’ marks was regulated, although such marks have also been encountered somewhat before this date. medium A liquid or viscous agent used to bind pigments and dyes to create paint. Types o f media used for paintings include egg tempera, glue, and oil. Emulsions, such as mixtures of oil and egg, or oil and glue, have also been postulated as binding media for early Netherlandish painting, but recent research has cast doubt on this theory (see further the essay by Molly Faries). medium analysis, see Fourier transform-infrared spectroscopy, gas-liquid chromatography, Raman spectroscopy, scanning electron microscopy, staining techniques microphotograph, see photomicrograph microscopy, see analytical microscope, stereomicroscopy mordant gilding, see gilding GLOSSARY

multispectral imaging An analytical technique to concurrently use numerous wavelengths in the electromagnetic spec­ trum, usually calibrated by the use o f narrow- and broadband filters. In theory, wavelengths that can be included are the ultraviolet and near-ultraviolet (i.e., that portion near the visible spec­ trum), and different ranges from the near- to far-infrared. While some art materials may appear visually similar, they may differentially absorb and reflect light in specific parts of the visible spectrum or in the invisible ultraviolet and infrared wavelengths. Multispectral imaging can use these differences to graphically separate different materials. near-infrared (NIR), see also infrared photography, infrared reflectography The infrared radiation closest to visible light, used for infrared photography and infrared reflectogra­ phy devices. normal light, see visible light oil medium/oil paint Paint with oil as a binding medium. The oils used in oil paint are drying oils that harden upon exposure to air. The hardening results from the chemical change that occurs when the oil film is exposed to oxygen, not from the evaporation of a volatile component. The most commonly used oil in early Netherlandish painting was linseed oil (from the seeds of the flax plant), but wal­ nut oil was also used. Most oils yellow over time, and to avoid this, oil was often heated between 250° and 300°C. Such polymerized oil is called “stand oil” or “heat-bodied oil.” It has been sug­ gested that heat-bodied oil accelerates drying, improves handling properties, and adds gloss to the paint. overpainting, see inpainting, ultraviolet light paint A coloring agent (such as a pigment or dyestuff) mixed with a binding medium. paint layer/paint-layer structure, see also anatomy o f a painting In its simplest form, a painting can consist of a single layer of paint. Most early Netherlandish paintings are more complex, however, and are comprised of several, superimposed paint layers and glazes. These individual paint layers can vary greatly in thickness. paint sample A piece of paint removed from an object for certain types of scientific analyses. A large sam­ ple is usually no bigger than the period at the end of this sentence. So that sampling sites remain inconspicuous, samples are usually collected from areas of damage or the edge of the image plane, which will be hidden by the frame. panel, see support pentimento, see also compositional change Italian for “regret.” This term is frequently used to refer to intentional adjustments or design changes made by an artist when executing a composition, especially original renderings that are now partially visible and/or have become more apparent over time with an increasing trans­ parency of subsequent paint layers. Technical methods of investigation such as infrared reflectogra­ phy and X-radiography are currently used for revealing compositional changes that have previously been obscured. It may be appropriate to use the term “pentim ento” when referring to changes that have accidentally become visible, since this is something an artist might very well regret. Using the term, however, when describing changes only made visible in documents produced by exami162

GLOSSARY

nation methods is erroneous, since these changes may belong to an artist’s routine method of working and would therefore have been expected. photomacrograph Close-up photograph, reproduced at the actual size of the object or larger. photomicrograph Photograph taken through a stereo- or analytical microscope, or with a scanning electron micro­ scope. pigments Microscopic, colored particles that give paint its hue. Pigments can be finely ground minerals, semiprecious stones, dyes laked onto a mordant, or synthetically manufactured compounds. pouncing A mechanical method for 1:1 transfer of compositions or motifs. Tiny holes are pricked along the main contours of a drawing and sometimes through to a separate interleaf used for transfer. The pricked sheet is laid on a panel’s ground, and charcoal dust or dark pigment contained in a porous fabric bag (the pounce bag) is patted through the holes to transfer the dots. The dots may or may not be connected in a second stage of underdrawing. In theory, the charcoal dust or pig­ ment is later brushed away, but pouncing dots remain in many early Netherlandish works and can be seen with infrared reflectography. Sometimes a ground is first made tacky so that the dots are fixed. For further discussion as well as an example of pouncing, see the essay by Molly Faries in this publication and her figure 9. press brocade (pi. 30), or applied relief brocade A decoration in relief, with a pattern molded into metal foil and applied in sheets to the sur­ face of a painting or sculpture. The relief patterns were prepared in carved molds. Tin foil was first pressed into a mold, which was then filled with a packing (in some cases, analyzed as wax and glue).After removal from the mold, the pattern could be applied to the desired surface with adhesive and then gilded, painted, or both. Although commonly found in sculpture, some exam­ ples of press brocade still exist in early-fifteenth-century Netherlandish painting, including the Ghent Altarpiece, in which it appears in the backgrounds of the panels with the Virgin Mary, the Deity figure, and John the Baptist. priming, see also isolation layer In early Netherlandish painting, the layer(s) that seals off or isolates the ground from the paint layers proper. It is usually applied on top of the underdrawing but can also be underneath, in which case it would also serve as a drawing surface. Primings can vary in substance and appearance: they can be uncolored, medium-rich and translucent; pure white; or very slightly pigmented with black and/or red, thereby either enhancing or toning down the white of the ground. Since priming layers are very thin, it has been difficult to test for medium, but both oil and protein (of egg or glue) have been detected. Priming pigmented with red and black would have been the same mixture as that used for pinkish skin color and therefore similar to the “fleshcolored” primuersel Karel van Mander stated was characteristic of the works of his predecessors. Priming is not necessarily synonymous with the term “imprimatura” in Italian treatises, since that apparently had a stronger coloring function. Further confusion arises because some authors describe the application o f a ground (especially to canvases) as priming. quarter-sawn, or radially sawn Wood sawn perpendicular to the growth rings o f a tree, to minimize shrinkage and warping. Quarter-sawn planks permit dendrochronology of the panels cut from them since the tree’s growth rings are visible on their end grains. See further the article by Peter Klein. GLOSSARY

163

raking light (fig. 8) The illumination of a painting from one side only so that the light falls across the surface and emphasizes the texture and varying thickness­ es of paint as well as deformations of the paint or the panel. Raking light can be used for pho­ tomicrography and photomacrography as well. Raman spectroscopy Raman spectroscopy measures the wavelength and intensity of inelastically scattered (Raman) light from molecules. In 1928, C.V. Raman dis­ covered this process, for which he was later awarded the Nobel Prize in Physics. As with all forms of spectroscopy, energy is supplied to the molecule, causing a release of energy at various wavelengths characteristic to that molecule.The energy in Raman spectroscopy is provided via a laser to the subject under investigation, and the Raman scattered energy is collected by a detec­ tor. Although possessing a different mechanism, Raman spectroscopy is a complimentary tech­ nique to infrared spectroscopy. For the examination of artworks, the laser is often directed through a microscope to allow a small and precise analysis location.The analy­ sis is nondestructive and is usually used to deter­ mine the nature of pigments and dyes.

Fig. 8. A lb rech t B outs, The M an o f Sorrows, m id 1490s. O il on w ood panel, 37.7 x 26.5 cm. Fogg Art M useum , 2001.170. D etail u n d er raking light, illu­ m inated from the left.

retouching, see inpainting sample, see paint sample, cross section sapwood, see also dendrochronology, growth ring The soft layer of wood inside a tree’s bark and cambium and outside of its heartwood. The num­ ber of sapwood rings varies among species and from region to region. W hen the bark and sapwood are removed from planks destined to be panels, evidence of the youngest growth rings is eliminated, which makes an exact determi­ nation of a felling date impossi­ ble. See also the articles by Peter Klein and Molly Faries. scanning electron microscope (SEM) (fig. 9), see also electron beam microprobe Microscope capable o f very high magnifications (see, e.g., fig. 1 in the essay by Molly Faries) and capable o f per­ forming elemental chemical analysis. In scanning electron microscopy, a beam of electrons is scanned in parallel lines across 164

GLOSSARY

Fig. 9. A scanning electron m icroscope at Harvard University.

a sample and interacts with it in several ways. Part of the beam causes electrons to be ejected from the sample and yield topographical information similar to that o f a reflected light microscope but at greater magnification, up to 100,000x and higher. Some of the electrons from the beam are reflected off the paint sample, and the “image” from these electrons provides information about the distribution of lighter and heavier elements in the sample. Other electrons generate X-rays in the sample, which may be collected and separated to identify specific elements. scumble A light, cloudy layer of opaque paint applied over a darker underlayer. The dark underlayer tends to give the upper layer a cooler tone. size Glue made from boiled animal skins or parchment clippings. squaring A mechanical method for 1:1 duplication and rescaling of compositions or motifs. To enlarge motifs for transfer, a square grid is drawn on the model or pattern and a larger grid on the ground­ ed surface of another panel or canvas. By finding the appropriate square, an artist or shop assistant can position and sketch in the main lines of the model, thus transferring the composition section by section. Compositions can also be downsized by this means, as we know occurred in some com­ positional replicas produced in Jan van Scorel’s workshop; see further the essay by Molly Faries. Measuring and establishing proportional relationships is one way of proving that squaring was used. Other forms of technical investigation may not always detect it, although infrared refiectography has disclosed examples of squaring in underdrawings drawn in dark materials. Although squaring has been known since antiquity, Leon Battista Alberti claimed the invention of this method for him­ self in his 1435 treatise on painting. staining techniques A traditional method using an analytical micro­ scope and stains to identify the organic compo­ nents within a paint sample. Stains are colored compounds that bond to different classes of mol­ ecules such as carbohydrates, lipids, and proteins. Chemical stains and fluorescent stains alike attach themselves to the organic components of the paint layer. Elements affected by chemical stains can be observed in white light under the micro­ scope; an ultraviolet light source is required to view paint components colored by fluorescent stains. Stains can be used in conjunction with spot tests for a particular binding medium. They are often used on paint cross sections to identify the broad class of binding medium in paint (see pis. 23,25).They can be used to identify mixtures of media in one layer of paint or different media in successive layers. The interpretation o f stain­ ing, at times subjective, requires that the prac­ titioner be highly experienced. stereomicroscopy (fig. 10) A technique that examines paintings at rel­ atively low magnifications (10—60x), revealing cracks, inpainting, and other surface details.The GLOSSARY

165

Stereo- or binocular microscope uses two oculars, allowing for viewing of the surface in three dimensions. A stereomicroscope can be outfitted with a photocamera for documentation, but photomicrographs record only a monocular, two-dimensional view. support The underlying structural foundation of a painting. Netherlandish paintings were typically painted either on oak panels or very fine linen (tiichlein). Oak for such panels was typically import­ ed from the Baltic and is thought to have been shipped as planks and made into panels by local cabinet or panel makers. Planks used for early Netherlandish paintings were rarely wider than 25—30 cm and thicker than 1—2 cm. Small paintings were often composed o f single planks of wood, but the supports for panel paintings were more typically several planks glued and joined to each other (see join /joining). To prevent warping, the outer edge (i.e., closer to the bark) o f one plank was often abutted with another’s outer edge (see fig. 3 c in the article by Peter Klein). Generally, planks run in the longer direction of the panel. It is imperative to study the edges and backs of panel paintings. Unless planed down and/or covered by cradling, the back of a panel will yield important information about its construction. Original panel reverses may also show traces of woodworking tools, brands (see marks), or bevel­ ing at the edges for insertion into frames. In altarpieces, the support o f the middle panel was usually thicker (up to 3.5 cm) while the wings were thinner, and thus lighter. Correspondingly, the frame of the middle panel was usu­ ally larger and that of the wings, smaller. Reverses o f middle panels were usually left unground­ ed, while wings were grounded and painted on both sides. tenting A raised, tentlike section o f paint formed along cracks in a painting. Tenting paint should be secured to avoid flaking. thin section, see cross section tracing, see also copying routines A mechanical method for 1:1 transfer of compositions or motifs. The back of a model draw­ ing, or the back of a separate interleaf, is blackened with charcoal or black chalk, more or less like modern carbon paper. Then the lines are traced with a stylus from the front of the sheet to transfer the main contours to the ground of a panel or canvas. The lines that result are exact but often show the painstaking nature of the copying process: they may break at intervals or appear hesitant (see, for instance, fig. 8 in the essay by Molly Faries). As with pouncing, it may be possi­ ble to brush away the charcoal or chalk after it has been reinforced in a subsequent stage of the underdrawing, thereby obliterating or obscuring the evidence of the transfer process. Early sources such as Cennino Cennini (c. 1390) mention the use o f oiled paper, parchment, or sheets o f gelatinous, dried animal glue for copying existing works. The translucent sheets were applied to the object to be copied and the desired forms traced onto them. tiichlein A painting executed on a fine linen support.The standard binding medium used with this type of support (German for “small cloth”) was glue distemper, and paint was often applied straight onto the canvas— or onto a very thin intermediary ground layer— and left unvarnished. Because of their fragile nature, few tiichlein have survived, and those that have are often in poor condition.They may have possessed some sort of backing or strip frames on the image side. ultraviolet (UV) light Invisible radiation just below the blue violet portion o f the range visible to the human eye in the electromagnetic spectrum, that excites fluorescence of materials on the surface of a painting. This fluorescence is visible to the naked eye and can be documented with photography. 166

GLOSSARY

Various paint colors and varnishes fluoresce differently, allowing for the detection o f areas of cleaning, retouching, and overpainting. Recently applied paint usually absorbs ultraviolet light and appears dark, while old varnish often fluoresces strongly. Since ultraviolet light does not pene­ trate further than the uppermost layer, it cannot detect any damages that might lie deeper in the paint layer structure.Very old overpaintings often also go undetected. Examination under UV light can sometimes provide additional information to identify cer­ tain pigments. UV light is also used to study the fluorescence from pigments, media, paint, and varnish layers in cross sections under the microscope. underdrawing The layout drawing an artist makes on the ground of a painting prior to applying paint. Unlike other types of preparatory drawing, the underdrawing is made to scale and is not autonomous; it is the first of the pictorial stages leading to the final image. Although an artist need do no more than mark the position of forms, underdrawings are often quite fully worked out. Researchers of underdrawings have noted that they frequently seem more expressive than the paint surface, perhaps because they were executed relatively rapidly and represent a stage when the composi­ tion was still evolving. Underdrawing can be executed in contour lines only, but often shadow is also rendered by sys­ tems of hatching or cross-hatching. A variety o f different materials is used for underdrawings, both dry and liquid. Brush drawings are made by applying a water-soluble pigment (or diluted ink) with a fine brush. The brush can be used to create very fine, linear strokes or broad areas of wash. Carbon black ink is an ink made by combining soot or charcoal with water that has been mixed with a binding agent such as gum arabic or glue. Since carbon is an inert material, the ink is chemical­ ly very stable. Natural chalks consist o f a pigmented material in a clay base. Black chalk is a combination o f carbon and clay. It can be cut into sticks that produce lines that are fine and pre­ cise or broad and indistinct. R ed chalk is a combination o f iron oxide and clay. Its color ranges from pale red to brownish orange. W hite chalk consists of calcite or calcium carbonate. It has a soft consistency and is generally used for highlights on drawings. Soapstone or steatite (both slightly harder than chalk) and graphite can also be used, as well as metalpoints. Charcoal is pro­ duced when bundles of sticks are heated in airtight chambers. It is soft and easily smudged and is most useful for broad rapid preliminary sketching. See further the essay by Molly Faries. undermodeling Strictly speaking, a monochromatic underlayer toned by the addition of black. In some early Netherlandish works, greens and blues, and occasionally reds, have been found to have gray paint layers underneath the surface color. Such underlayers deepened the final color and added to its opacity, contributing to the modeling o f volumes. W hen underdrawings are shaded extensively with washes, they can also function as a form of undermodeling. Some authors also use the term “undermodeling” to allude to the way under­ painting can model, or suggest light and dark, in the underlying paint stages. Infrared reflectography can sometimes reveal undennodeling; see further the examples cited in the essay by Molly Faries. underpainting, see also dead color A colored paint underlayer. Underpainting is frequent in the superimposed paint-layer structure o f early Netherlandish painting. Generally, underpainting, in one or more layers, is a tint o f the final color, which takes the form o f an opaque layer or a glaze. Underpainting is therefore a basic component of early Netherlandish painting practice, in which artists paint from light to dark. U nderpainting can occur in any color or color mixture: such as a m ixture o f blue and white under a dark blue; a mixture o f red and white under a dark red final layer; a red-orange mixture of vermilion and red lake under a red glaze; or even a different color from the final GLOSSARY

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color, such as yellowish or reddish layers under green. Underpainting layers often contain cheap­ er materials or more finely ground pigments. By varying the thickness or the amount o f white, artists could begin to work up the darker and lighter areas o f forms in the underpainting stage. Since underpainting usually contains a significant amount o f lead white, it can be detected by X-radiography. varnish A clear coating applied as a final layer to a painted surface to saturate and protect it. Tradi­ tional varnishes are formed of natural resins, and most (e.g., mastic, sandarac, dammar, and pine balsams) derive from living trees. Evidence exists that varnishes have been used since ancient times; recipes from the Middle Ages describe the preparation o f oil varnishes (dissolving the resin in a drying oil such as linseed). Spirit varnishes (i.e., resins dissolved in spirits of turpentine) did not come into use until the sixteenth century. vidicon, see infrared vidicon vidimus A presentation drawing shown for approval to the person or group commissioning a work. In a strict legal sense, it refers to the model drawing attached to the contract between artist and client. In Dutch documents, such a drawing is called a “patroon” or “bewerp.” Since a painting could be shown to a commissioner at various stages o f completion, an underdrawing could also function as a vidimus. Like the model drawing accompanying the contract, an underdrawing pre­ dicted the entirety o f the final composition and could be judged before the application o f expen­ sive paints. Some underdrawings by Jan van Eyck and other artists have been interpreted as vidimuses; see further the essay by Molly Faries. visible light, see also electromagnetic spectrum A form o f electromagnetic radiation; only a narrow band o f the electromagnetic spectrum is visible to the human eye. Colors within the range o f visible light can be distinguished by their wavelengths and range from violet (about 400 nanometers) to red (about 700 nanometers). Infrared light, ultraviolet light, and X-rays are forms of electromagnetic radiation, which are invis­ ible to the human eye and which are used in the examination of paintings. Infrared radiation has a slightly longer and ultraviolet a slightly shorter wavelength than the visible region on the spectrum. wavelength, see also electromagnetic spectrum The characterization o f radiation on the electromagnetic spectrum. Forms o f radiation can be distinguished by wavelength and range from kilometers-long radio waves to very short gamma waves, which are usually measured in nanometers (one nanometer equals one-billionth o f a meter). O ther units o f measurement that are used to describe wavelengths are pm (micrometers/microns) and A (angstroms). wavelength-dispersive spectroscopy (WDS), see X-ray fluorescence wet-in-wet A painting technique whereby paint strokes o f one application are blended or swirled into another color or layer that is not fully dry. In cross sections, the demarcation between layers of wetin-wet painting will often appear blurred. X-radiography A technique that displays absorbency patterns of X-rays (see electromagnetic spectrum) on films known as X-radiographs. In 1895, the German physicist W. C. R öntgen discovered a highly 168

GLOSSARY

penetrating invisible radiation that he called X-rays (with X standing for unknown, since he erro­ neously thought these rays were unrelated to other forms of electromagnetic radiation). In the electromagnetic spectrum, X-rays (between approximately 3 and 0.03 nanometers) are located between the ultraviolet and the gamma rays. X-rays register on photographic emulsions, and individual materials absorb X-rays to differ­ ent degrees. Areas of paint that contain elements with a high atomic weight, such as lead white, lead-tin yellow, or vermilion, will absorb the X-rays and block them from blackening the film, thus appearing as light areas on the X-radiograph. Materials that do not absorb, i.e., are trans­ parent to, the X-rays, will allow X-rays to pass through the object to blacken the film. Metal objects such as nails or other hardware register as fully X-ray opaque, but the gold leaf used in water or mordant gilding is usually too thin to register in X-radiographs. X-radiography can reveal the presence of compositional changes from an earlier stage in the paint­ ing process since areas in which X-ray opaque materials were later covered with materials that are more X-ray transparent will still absorb the X-rays and appear light on the X-radiograph. In addition to information about the pigments that were used in a painting, X-radiography can also reveal ample inform ation about a painting’s support and on other aspects o f technique. For example, it can reveal dowels in the panel support and additions made to the original support. X-radiography can also detect the presence of incisions in any of the paint layers; these will appear as either dark or light lines, depending on whether the incisions have become filled with X-ray absorptive materials. Paintings were among the very first objects to be examined with X-rays.To obtain an X-radiograph, the painting is placed between a source emitting X-rays and a film sheet. Usually the film is placed directly against the painting’s surface, thus providing a precise 1:1 image. X-ray diffraction analysis (XRD) An analytical technique to determine the chemical and physical composition of a sample hav­ ing a crystalline structure. X-ray diffraction analysis identifies the crystalline materials from their molecular structure. A beam of single-wavelength X-rays is fired into the sample, and the X-rays are spattered according to the size and spacing o f the sample’s atoms, giving a diffraction pat­ tern. The pattern, specific to the sample being analyzed, is collected either electronically or on film and then compared to a library of standards for identification. A paint sample is required and cannot usually be retrieved after analysis, although recently, diffractograms have been collected nondestructively from objects. X-ray fluorescence (XRF) (figs. 11a and b) W hen an electron beam from a scanning electron microscope, an electron beam microprobe, or an X-ray beam from an X R F spectrometer hits an atom of a paint sample, electrons from the sam­ ple are temporarily bumped into a higher energy state. W hen the electrons fall back to a lower state, they emit the excess energy as X-rays, know n as fluorescence. The emission o f X-ray fluorescence is unique for each chemical element. There are two ways to analyze X-ray fluorescence: energy-dispersive X-ray analysis (EDX) (also known as energy-dispersive spectroscopy, EDS) and wavelength-dispersive spectroscopy (WDS). In EDX (fig. 11a), the emitted X-ray fluorescence is collected directly from the object by the detector. This allows for the identification o f pigments and other components such as metallic leaf, yielding qualitative (or semiquantitative at best) results. Qualitative results indi­ cate the presence or absence of a material; quantitative results indicate the amount o f a sub­ stance. This technique can be a nondestructive m ethod o f analysis, since it does not always require taking a sample. In WDS (fig. lib ), in contrast, X-ray fluorescence is collected by the detector after being bounced offa crystal of known structure.The crystal or the detector rotates through its circular range, detecting different angles of bounce for the fluorescence and measuring the angle of reflec­ tion. The angle is related to the energy of the fluorescence and is unique to the element under GLOSSARY

169

c o m p u te r p ro c e sso r

- jH v

Fig. 11. Schematic representation o f (a), energy-dispersive X -ray analysis (EDX), and (b), wavelength-disper­ sive spectroscopy (WDS).

analysis. In figure lib , 0 is the angle of bounce, recorded as 20 vs. intensity. 20 is the convention for recording the angle of bounce. Scanning the 20 range allows for the acquisition of the com­ plete spectrum. Five crystals are required to detect all the elements in the periodic table. The results from this type of analysis yield quantitative results. The sample is subjected to high-ener­ gy bombardment, so organic materials are destroyed but most inorganic materials (such as metallic leaf or pigment) survive well. X-rays, see X-radiography

170

GLOSSARY

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191

PLATES

Faries

Plate 1. Globules o f lead-tin yellow im itating high­ lights on metal; detail o f the hand o f Eve in a paint­ ing in the Petrus C hristus group, Madonna in an Archway, M useum Boijmans Van Beuningen, R o tte r­ dam, 3316. Photom icrograph, 3.6x on 35m m film.

Plate 2. Strands o f lead -tin yellow im itating gold threads; detail o f the brocade o f Saint Nicholas in Ger­ ard David, Saint Anne Altarpiece, N ational Gallery o f Art, W ashington, D.C., 1942.9.17.a—c. P hotom icro­ graph, 3.9x on 35m m film.

Plate 3. Cross section w ith an upp er layer o f ultram arine blue on a pinkish underpainting from Jan van Scorel’s Baptism of Christ, Frans Halsmuseum, H aar­ lem, 265. Photom icrograph, lOOx actual size.

195

Spronk

Plate 4. Master o f the H oly Blood, Saint Luke Painting the Portrait o f the Virgin, c. 1520. Oil on oak panel, 43.6 X 32.2 cm. Fogg Art Museum, Harvard University, Cam­ bridge, Massachusetts, 1910.6. Detail o f the palette.

196

Plate 5. M aster o f the H oly Blood, Saint Luke Paint­ ing the Portrait of the Virgin, Fogg A rt M useum . Detail o f the head o f the Virgin showing underdrawing.

H e n s ic k

Plate 6. C opy after Jan van Eyck, Woman at Her Toilet. O il on oak panel, 27.5 x 16.5 cm. Fogg A rt M useum , Harvard University, Cam bridge, Massachusetts, 1969.83.

197

H e n s ic k

Plate 7. Verso o f C opy after Jan van Eyck, Woman at Her Toilet, Fogg A rt M useum .

Plate 8. (a) Detail o f W illem van H aecht, Tire Cabi­ net o f Cornelis van der Gheest, R ubenshuis, A ntwerp, show ing Woman at Her Toilet, (b) D etail after digital m anipulation to eliminate some o f the effects o f fore­ shortening.

198

H e n s ic k

Plate 9. Peter Klein exam ining the support o f Woman at HerToilet at the Straus C enter for Conservation, Harvard University A rt M useums, Cam bridge, Massachusetts.

Plate 10a. Photom icrograph o f cross section no. 1 o f C opy after Jan van Eyck, Woman at Her Toilet, Fogg A rt M useum ; sample taken from the um ber floor in foreground. U ltraviolet illum ination, m agnification 250x on 35m m film. 1. Carbon black, yellow ochre, lead white, lead-tin yel­ low. 2. Lead w hite, calcite, ochre. 3. Lead-tin yellow. 4. C halk w ith fossils.

Plate 10b. Photom icrograph o f cross section no. 10 o f C opy after Jan van Eyck, Woman at HerToilet, Fogg A rt M useum; sample taken from the chair in the low­ er left. M agnification 64x on 35m m film. 1. Bone black, ochre. 2. V erm ilion, red ochre, b o n e black, yellow ochre, calcite. 3. Lead-tin yellow, lead white. 4. Chalk.

199

P o c o b e n e /Spronk

Plate 11. W orkshop o f D irk Bouts, Virgin and Child. O il (and tempera?) on w ood panel, 30.5 x 21.6 cm. Fogg A rt M useum , Harvard University, Cam bridge, Massachusetts, 1959.186. Gift o f Mrs. Jesse Isidor Straus, in m em ­ ory o f her husband, Jesse Isidor Straus, class o f 1893.

200

P o c o b e n e /S p r o n k

Plate 12. W orkshop o f D irk Bouts, Virgin and Child, Foss; A rt M useum . Before treatm ent.

Plate 13. W orkshop o f D irk Bouts, Virgin and Child, Fogg A rt M useum . D u rin g treatm ent, varnish partly removed.

Plate 14. W orkshop o f D irk Bouts, Virgin and Child, Fogg A rt M useum . D etail o f the top edge, d u rin g treatm ent. 1. O riginal paint surface. 2. Lead putty fill m aterial, covering original paint. 3. Lead putty fill, partly removed. 4. Vermilion border. 5. Chalk-glue ground in old abraded area.

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G i f F o r d / H a l p i n e / L o m a x / S c h i l lin g

Plate 15. N etherlandish c. 1400, The Annunciation. O il on panel, 36.4 x 25.9 cm, Walters A rt M useum , Balti­ m ore, 37.1683A.

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G i f F o r d / H a l p i n e / L o m a x / S c h il lin g

Plate 16. Netherlandish c. 1400, The Baptism of Christ. O il on panel, 36.4 x 25.9 cm, Walters A rt M useum , Baltimore, 37.1683B.

Plate 17. N etherlandish c. 1400, The Crucifixion. O il on panel, 34 x 25.4 cm excluding w ood additions to upper and lower edges, Walters A rt M useum , Balti­ more, 37.1683C.

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G i f F o r d / H a l p i n e / L o m a x / S c h i l lin g

Plate 18. The Annunciation, glazed details o f G abriel’s w ing painted over tooled gold leaf, photomicrograph, magnification 2.2x on 35m m film.

Plate 19. Tlie Annunciation, G abriel’s red drapery, detail.

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G ifF o r d /H a lp in e /L o m a x /S c h illin g

Plate 20. Tite Baptism o f Christ, glazed water, detail.

Plate 21. Tite Annunciation, w et-in-w et painting o f the throne, ph o to m icro g rap h , m agnification 2.2x on 35m m film.

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G i f f o r d / H a l p i n e / L o m a x / S c h i l lin g

Plate 22. The Annunciation, paint cross section from an architectural detail o f the V irgin’s throne, p h o to m i­ crograph, visible light. From the lowest layer: chalkglue ground; w h ite lead isolating layer; w hite lead paint o f the throne; shadow detail (brow n earth) swirled w et-in-w et into the w hite at the upper right. N o te that the isolating layer cannot be distinguished by visible light; see plate 25. (Plates 22-25: WAM sam­ ple no. 1406; magnification 78x on 35m m film.) Plate 23. Paint cross section in plate 22 stained w ith amido black, photom icrograph, visible light. A posi­ tive blue stain indicates a glue m edium in the chalk ground layer. Plate 24. Paint cross section in plate 22, photom icro­ graph, autofluorescence. Plate 25. Paint cross section in plate 22, stained with the fluorescent stain 2,7 dichlorofluorescein, p h o to ­ micrograph, auto fluorescence. A strongly positive reac­ tion reveals the oil-rich isolating layer. W ith o u t the confirm ation o f G C -M S analysis, the faint results in the paint layer could have been interpreted as a neg­ ative reaction.

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Plate 27. Gerard David, Virgin and Child with the M ilk Soup, c. 1515. O il on w ood, 33 x 27.5 cm. Aurora Art Fund, N ew York.

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G lo s s a r y

Plate 28. D ip ty ch : Follow er o f R o g ie r van der W eyden, Virgin and Child (left panel, 55.5 x 35.7 cm); Follower o f Gerard David, Portrait of a Donor (Joos van der Burch) and a Bishop Saint (right panel, 56.3 x 35.5 cm), c. 1480. O il (and tempera?) on w ood panel. Fogg A rt M useum , Bequest o f G eorge W. H arris in m em o ry o f Jo h n A. H arris (to H arvard C ollege), 1906.6a,b. D etail o f the left edge o f the right panel w ith unpainted edge (1) and barb (2). For an illustra­ tio n o f the full diptych, see fig. 3 in R o n S pronk’s article.

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G lo s s a r y

Plate 29. M aster o f the Saint Ursula Legend, The Virgin and Child with Angels, c. 1490. O il o n w ood panel, 41.4 x 29.7 cm. Fogg A rt M useum , Bequest o f Grenville L. W inthrop, 1943.97. Plate 29a. Detail o f the top left background. O n top o f the water-gilded background, raised, gilded rays were added w ith m ordant gilding. Plate 29b. P hotom icrograph from the outlined detail in plate 29a. T he black arrows indi­ cate remnants o f the viscous oil m ordant that was applied on top o f the background gild­ ing to raise these features and to adhere the gold leaf. T he yellow arrow points to a scratch in the background gilding w here the ground layer has becom e visible. T he background gilding was applied w ith o u t a bole.

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G lo s s a r y

Plate 30. H u b e rt and Jan van Eyck, Ghent Altarpiece, 1432 (St. Bavo’s Cathedral, G hent). D etail o f press brocade from the right edge o f the panel w ith the Virgin E nthroned.

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Illustration Credits

Cover design: R o n Spronk; photographs © President and Fellows o f Harvard College Faries Fig. 1 Catherine Metzger Figs. 2, 3, 6—9 © Molly Faries Fig. 4 from Marijnissen 1985, 157 Fig. 5 © Peter Klein Plates 1,3 © J. R . J. van Asperen de Boer Plate 2 Catherine Metzger, courtesy National Gallery o f Art, Washington, D.C. Spronk Figs. 1—3 ,5 ,6 ,1 2 Digital Imaging andVisual Resources, Harvard University Art Museums © President and Fel­ lows o f Harvard College Figs. 4, 13, 14, plates 4, 5 R o n Spronk © President and Fellows o f Harvard College Fig. 7 © Trustees o f the M useum o f Fine Arts, Boston Fig. 8 R hona M acBeth © Trustees o f the M useum of Fine Arts, Boston Fig. 9 Harvard University Archives © President and Fel­ lows of Harvard College Fig. 10 Alan Burroughs © President and Fellows o f Har­ vard College Fig. 11 Lotte Jacobi, courtesy Harvard University Archives Fig. 15 courtesy Craig H ugh Smyth van Asperen de B oer Figs. 1 ,3a—c, 4, 5 © J. R .J. van Asperen de Boer Fig. 2 © Royal Cabinet o f Paintings, Mauritshuis, The Hague/Koninklijk Instituut voor het Kunstpatrimonium, Brussels Klein Figs. 1—15 © Peter Klein H ensick Fig. 1, plate 8a © Stad A ntw erpen, Kunsthistorische Musea, Rubenshuis Fig. 2 ©Trustees,The National Gallery, London Fig. 3, plate 7 Straus Center for Conservation andTechnical Studies, Harvard University Art Museums © Pres­ ident and Fellows o f Harvard College Figs. 4, 5 © Courtauld Institute o f Art Figs. 6,7, plate 6 Digital Imaging andVisual Resources, Harvard University Art Museums © President and Fel­ lows of Harvard College Fig. 8, plates 9 , 10a,b Teri Hensick © President and Fel­ lows of Harvard College Fig. 9 Eugene Farrell © President and Fellows o f Har­ vard College Plate 8b R o n Spronk © President and Fellows o f Har­ vard College

P ocob en e/S p ron k Figs. 1 ,7a R o n Spronk © President and Fellows o f Har­ vard College Figs. 2, 9, 10, plates 11—13 Digital Imaging andVisual Resources, Harvard University Art Museums © Presi­ dent and Fellows o f Harvard College Fig. 3 Ursula Edelmann © Städelsches Kunstinstitut, Frankfurt am Main Figs. 4,6 © Städelsches Kunstinstitut, Frankfurt am Main Figs. 5 ,7b Eugene Farrell/R on Spronk © President and Fellows o f Harvard College Fig. 8, plate 14 Gianfranco Pocobene © President and Fellows o f Harvard College G ifF ord/H alpine/L om ax/Schilling Plate 15 Harry Connolly © The Walters Art Museum, Baltimore Plates 16, 17 Susan Tobin © The Walters Art Museum, Baltimore Plates 18—25 © Melanie Gifford Lie Figs. 1—3, 5, plate 26 R on Spronk © President and Fel­ lows o f Harvard College Fig. 4 Henry L ie/R on Spronk © President and Fellows o f Harvard College Figs. 6—14 Henry Lie © President and Fellows o f Har­ vard College Ainsworth Figs, la—c, 8, 9 © Maryan W. Ainsworth Fig. 2 Photoatelier Jörg P. Anders © Staatliche Museen Preußischer Kulturbesitz, Gemäldegalerie, Berlin Figs. 3,5 ©The Metropolitan Museum ofArt, New York Fig. 4 ©Trustees,The National Gallery, London Fig. 6 © National Gallery ofArt,W ashington, D.C. Fig. 7 © Palazzo Bianco, Genoa Plate 27 © Aurora Art Fund. Photo courtesy o f Stiebei, Ltd. Glossary Figs. 1—6, 10, 11, plates 29a,b R ichard M ulholland © President and Fellows o f Harvard College Fig. 7 courtesy Micha Leeflang Fig. 8 Gianfranco Pocobene © President and Fellows of Harvard College Fig. 9 David Lange © President and Fellows o f Harvard College Plate 28 R on Spronk © President and Fellows o f Har­ vard College Plate 30 © J. R .J. van Asperen de Boer

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