Effects of Light on Materials in Collections

Effects of Light Effects on Materials in Collections Data on Photoflash and Related Sources Schaeffer T. Terry The Getty Conservation Institute research in conservation GCI Effects of Light on Materials in Collections Schaeffer research in conservation The Getty Conservation Institute Effects of Light on Materials in Collections Data on Photoflash and Related Sources Terry T. Schaeffer 2001 Dinah Berland: Editorial Project Manager Elizabeth Maggio: Manuscript Editor Anita Keys: Production Coordinator Hespenheide Design: Designer Printed in the United States of America 10 9 8 7 6 5 4 3 2 © 2001 The J. Paul Getty Trust Second printing 2002 Getty Publications 1200 Getty Center Drive, Suite 500 Los Angeles, California 90049–1682 www.getty.edu The Getty Conservation Institute The Getty Conservation Institute works internationally to advance conservation in the visual arts. The Institute serves the conservation community through scientific research, education and training, model field projects, and the dissemination of information. The Institute is a program of the J. Paul Getty Trust, an international cultural and philanthropic institution devoted to the visual arts and the humanities. Research in Conservation The Research in Conservation reference series presents the findings of research conducted by the Getty Conservation Institute and its individual and institutional research partners, as well as state-of-the-art reviews of conservation literature. Each volume covers a topic of current interest to conservators and conservation scientists. Other volumes in the Research in Conservation series include Biodeterioration of Stone in Tropical Environments: An Overview (Kumar and Kumar 1999); Inert Gases in the Control of Museum Insect Pests (Selwitz and Maekawa 1998); Oxygen-Free Museum Cases (Maekawa 1998); Accelerated Aging: Photochemical and Thermal Aspects (Feller 1994); Airborne Particles in Museums (Nazaroff, Ligoki, et al. 1993); and Statistical Analysis in Art Conservation Research (Reedy and Reedy 1988). Library of Congress Cataloging-in-Publication Data Schaeffer, Terry T. (Terry Trosper), 1939– Effects of light on materials in collections : data on photoflash and related sources / Terry T. Schaeffer. p. cm.—(Research in conservation) Includes bibliographical references and index. ISBN 0-89236-645-1 1. Art–Deterioration. 2. Artists’ materials—Effect of light on. 3. Photochemistry. 4. Archival materials—Deterioration. 5. Museum conservation methods. I. Title. II. Research in conservation (Unnumbered) N8558.5 .S33 2001 069.53—dc21 2001001977 Contents v Foreword Timothy P. Whalen vii Preface 1 Introduction Chapter 1 5 Background Information 5 Photophysics 10 Photochemistry 13 Light Sources 26 Filters Used with Light Sources 28 Considerations for the Calculations Chapter 2 35 Results of the Literature Search 35 Colorants 51 Natural Fibers 56 Pulp, Paper, and Wood 66 Gums and Natural Resins 67 Synthetic Polymers 78 Polymeric Materials Containing Colorants 102 Fluorescent Whitening Agents 108 Photographic and Reprographic Materials 122 Miscellaneous Objects and Combinations of Materials Chapter 3 126 Technical Details from the Literature Search 126 Colorants 131 Natural Fibers 132 Pulp, Paper, and Wood 136 Gums and Natural Resins 136 Synthetic Polymers 141 Polymeric Materials Containing Colorants 154 Fluorescent Whitening Agents 154 Photographic and Reprographic Materials 157 Miscellaneous Objects and Combinations of Materials iv Chapter 2 Chapter 4 158 Discussion 160 Assumptions Used for the Calculations 161 Assessing Risk 164 Suggestions for Further Action 169 References 199 Index 212 About the Author Foreword Among the many environmental conservation measures taken to protect objects in collections, the control of lighting levels has probably received the most unanimous agreement among conservators and conservation scientists. The more sensitive certain types of objects are, the more agreement exists that they be subject to general lighting guidelines that have been confirmed by scientific research. Yet despite these widely adopted standards, the conservation literature contains few reports of experiments designed specifically to address the effects of photoflash and reprographic light on works of art and archival objects. Terry T. Schaeffer’s thoughtful review of the literature fills that gap, allowing us to dispense with most lingering doubts on the subject. The calculations provided here on the duration, intensity, and frequency of photoflash and reprographic exposure allow us to conclude at long last that, for most materials at least, there are few deleterious long-term consequences. Any legitimate doubts that persist will have to be addressed in future research. The twentieth century witnessed a flood of new materials for art making, many of which did not take permanence into account. Objects containing these materials are now raising important questions regarding lightfastness and photochemical instability, and the twenty-first century promises to accelerate that trend. For some contemporary objects, photoflash and reprographic reproduction cannot be dismissed as insignificant. This review thus provides an in-depth examination of the photochemical sensitivity of very wide range of products. The Getty Conservation Institute originally commissioned this study for internal use. We were seeking a thorough literature review on lighting of modern and historical materials with an emphasis on photoflash to inform our own judgment in planning future materials research. When the review was completed, its potential value to the larger conservation community was recognized and a decision was made to publish it in the GCI’s Research in Conservation series. Conservators, curators, and collections managers are faced with constant challenges in establishing exhibition policies and in managing risk to sensitive materials. We hope this publication may assist in that endeavor by providing new data in some cases and making previously less-accessible information available in a single volume. Timothy P. Whalen, Director The Getty Conservation Institute Preface This publication was first inspired by a request for a proposal to perform a modest experimental investigation. The topic was to be the effects of photoflash light sources on materials in art and archival objects. The purpose was to identify highly sensitive materials and to determine the extent of flash exposure that might be considered “safe.” Concerns for possible deleterious consequences of light exposures due to flashlamps have been raised periodically in the conservation community. These concerns are frequently dismissed on the basis of simple calculations that use all-encompassing assumptions and anecdotal evidence, or by reference to fading data for materials that are not highly light sensitive. A brief search of the conservation literature indicated that numerical data existed for only a few types of materials that had been thoroughly investigated using well-defined flash exposures. However, the conservation literature, and especially the photochemical literature, contains a wealth of data on the effects of various light exposures on many substances found in art and archival collections. If the relevance of these data to exposures from photoflash and reprographic light sources could be established, then general guidelines regarding the efficacy of photoflash exposures might be deduced. A very large bibliography was amassed in the ensuing literature search, which was completed in spring 1998. A few more recent publications were also included. The data in the references were evaluated with respect to their implications for the effect of flash exposure. A set of carefully defined assumptions was established to enable evaluations to be done for many of the materials considered. Because little of the data reviewed here was obtained using flashlamps, or for materials and conditions normally found in museums, the results discussed must be considered order- of-magnitude guidelines only. In any specific situation, collections care professionals need to rely on their own expertise and judgment in applying the information presented. The information obtained in the course of interpreting the literature for the effects of photoflash proved to be more useful than anticipated; it became apparent that these data could also be used as a broad-based resource on light exposure of works of art and archival objects. Thus the entire bibliography and a variety of relevant background information on the effects of light on the materials considered were integrated here. The resulting publication is designed for museum personnel charged with devising general as well as specifically photographic light-exposure policies. viii Preface Acknowledgments I wish to extend my gratitude to the Getty Conservation Institute for supporting the perception that a more extensive search of the conservation and photochemical literature was needed and for encouraging the preparation of this volume, which contains much more information than originally envisioned. It is hoped that this material will eventually be accessible to all museum and archives professionals who make light-exposure decisions for their collections. The search could not have been completed without the support of the staff of the Getty Conservation Institute’s Information Center. My thanks to Carol Cressler, Valerie Greathouse, Teresa Negrucci, Thomas Shreves, Shannon Walker, and Jackie Zak for their consistently cheerful and willing help while they were dealing

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