IDENTIFICATION OF THE FORBES COLLECTION PIGMENTS: I. WHITES
Gary W. Carriveau, & Diana Omecinsky
ABSTRACT—A large group of pigments (approximately 6200 examples) was assembled by the late Edward Waldo Forbes, former director of the Fogg Art Museum. This collection contains well-known organic and inorganic pigments as well as a large number of rare and unusual Oriental specimens. From this large body of material, selected samples were distributed to various museums and other institutions throughout the U.S. and Canada. These pigments are commonly used both as a study collection and as conservation material. Following an informal study of the samples in the Detroit Institute of Arts' collection, we found that many were incorrectly identified or lacked identification. This led to a detailed study of the composition of the pigments and determination of their proper identification.
EDWARD WALDO FORBES, former director of the Fogg Art Museum at Harvard University, added continually to his collection of pigments during a lifetime of extensive travel. Of special importance is the collection of dry pigments purchased in Japan—some of which are rare and unusual to European painters. During his life, Forbes gave reference samples to the Fogg Museum, eventually forming the “core” or original Fogg Museum Collection. After his death, the rest of Forbes' collection was donated to the Institute of Fine Arts, New York University with the understanding that further samplings could be taken from it in order to provide material to other institutions. It has always been assumed that the NYU collection was essentially a duplicate of the Fogg collection; however, it appears that there are a number of materials in the NYU collection that are not in the Fogg collection and vice-versa. To date, a comparative list of both collections has never been published.
Further complications arise from undocumented additions made to the collections since it was dispersed. For this reason we would welcome contributions of pigment samples that would fill in the gaps that remain in our collection. It is important, in a study of this type, that an assembly as complete as possible be analyzed.
As presently understood, the disposal of samples from both collections is as follows:
- Fogg (core) Museum Collection:
Fogg Art Museum (Cambridge, Massachusetts)Intermuseum Conservation Laboratory, (Oberlin, Ohio)Balboa Art Conservation Center (San Diego, California)New York University Conservation Center of the Institute of Fine Arts (NewYork, New York)∗Art Institute of Chicago (Chicago, Illinois)Philadelphia Museum of Art (Philadelphia, Pennsylvania)
- New York University (Forbes' Private) Collection:
Metropolitan Museum of Art (NYC, NY)Winterthur Museum (Winterthur, Delaware)Walters Art Gallery (Baltimore, Maryland)Detroit Institute of Arts (Detroit, Michigan)∗Intermuseum Conservation Laboratory (Oberlin, Ohio)Carnegie-Mellon Institute (Pittsburgh, Pennsylvania)Freer Technical Laboratory (Washington, D.C.)Library of Congress Restoration Office (Washington, D.C.)∗National Gallery of Canada (Ottawa, Ontario, Canada)McCrone Research Laboratory (Chicago, Illinois)Cooperstown Graduate Programs—Conservation of Historic and Artistic Works (Cooperstown, New York)Doerner Institute (Munich, West Germany)University of Stellenbosch (Stellenbosch, South Africa)National Research Laboratory for Conservation (New Delhi, India)
Note: asterisk (∗) designates samples which have been mounted on slides for study/reference purposes.
The collection was originally numbered according to the second column on the NYU inventory sheets, (See example, Table I) under the rubric old: e.g. 133, 1331G, 146G. This system was revised by Richard Buck to those shown in the first column of the inventory under the rubric new: e.g. 1.01.1, 1.01.2, 1.01.3, etc. Under the new system the various colors are separated into clearly defined categories so that, for example, all whites begin with a 1; within this group the calcium whites begin with 1.01 and all the samples within this subgroup are numbered 1.01.1, 1.01.2, 1.01.3. (See Table I). Additional identification information is found in Table II.
Table I: Example of Collection Numbering System White (Code 1) Calcium Compounds (Code .01)
Table II: Whites
2 EXPERIMENTAL PROCEDURE
THE FIRST GROUP of pigments to undergo analysis were the whites. These were generally in the form of a dry powdered pigment of ground-up mineral. All but one were inorganic in nature and thus suitable for study using x-ray diffraction (XRD). To assist in the interpretation of the x-ray diffraction pattern data, energy dispersive x-ray flourescence (XRF) was used to study the elemental composition of some samples.
X-ray powder diffraction patterns of pigment samples were produced using Debye-Scherrer and Gandolfi (114.6 cm) cameras mounted on a Philips Model 12045 XRD generator. Copper Kα radiation, a potential of 30KV and 15 mA of current were used. The spacings and relative intensities were read off the film (Kodak: No-Screen film, NS-392T); the d-values were calculated from the data and compared to known values taken from the JCPDS Powder Data file1–5
X-ray fluorescence results were obtained using a Kevex Model 0750 system, which uses an energy dispersive solid state detector with excitation from a Rh anode x-ray tube using a variety of secondary targets.
3 RESULTS AND DISCUSSION
THE RESULTS of our studies are found in Table II. The following information is given:
- column 1: new numbering system (Buck)
- column 2: old numbering system (Forbes)
- column 3: pigment identification attributed to Forbes
- column 4: our pigment identification and JCPDS File Card No.
A dagger (†) denotes samples where x-ray fluorescence was used to assist x-ray diffraction pattern analysis.
For a number of pigments, there are significant differences between Forbes' identification (column 3) and our own.
The results in column 4 are complete except for two samples (1.05.2 and 1.05.5) that we were unable to obtain. In fact, our original collection of Forbes pigments contained only 39 of the white samples. It was only through the generous assistance of other museums and institutes that our collection is as complete as it is at this time. We would like to request further assistance from anyone having the missing Forbes pigments.
The following samples require additional comment since the XRD and XRF analysis gave inconclusive results.
3.1 Samples 1.02.5 and 1.02.9
The XRD pattern was taken using normal sample size; however, no discernable pattern other than the diffuse background was obtained. XRF provided qualitative elemental information as follows:
- sample 1.02.5 contains K, Na, Al, Si
- sample 1.02.9 contains A1
3.2 Sample 1.02.4
Identified by Forbes as Fullers Earth, gave XRD results indicating impure Si02. Fisher Scientific provided an analysis of their commercial Fullers Earth; it contains 64% SiO2, 16% Al2O, and oxides of Mg, Mn, Ca, Fe, Ti and Na.
3.3 Samples 1.10.3 and 1.20.5
The XRD patterns showed d-spacings similar to the general reflections characteristic of unoriented iron-rich montmorillonite. XRF data confirmed the presence of Fe and lack of K, which makes the sample dissimilar to the muscovites. The main difficulty in the identification of these two samples is that x-ray identification is not the best method for untreated and, therefore, unoriented clay mineral samples, especially montmorillonites.6
ONE AUTHOR (Diana Omecinsky) wishes to gratefully acknowledge the financial support of the Andrew W. Mellon Foundation. We also thank Gary Alden, Mary Calisto, Eugene Farrell, Thom Gentle, Michael Heslip, Laura Juszczak, Richard Newman, Philip Vance, and John Winter for their help in supplying Forbes pigment samples and information about the collection. We wish to thank Marta Baranyk and Richard Caldwell for their assistance in taking XRD data. We express our thanks to Jerri Nelson, Eugene Farrell, Christopher Tahk, and anonymous referees for their helpful comments and suggestions on this manuscript.
“Inorganic Index to the Powder Diffraction File.” ASTM PublicationPD15-17i. American Society for Testing and Materials, Philadelphia, PA, 1967.
“Inorganic Powder Diffraction File, Search Manual, Hanawalt Method.” JCPDS. International Centre for Diffraction Data, Swarthmore, PA, 1981.
“Powder Diffraction File, Alphabetical Index, Inorganic Phases.” JCPDS. International Centre for Diffraction Data, Swarthmore, PA, 1981.
“Mineral Powder Diffraction File, Search Manual.” JCPDS. International Centre for Diffraction Data, Swarthmore, PA, 1981.
“Mineral Powder Diffraction File, Data Book.” JCPDS. International Centre for Diffraction Data, Swarthmore, PA, 1981.
Carroll, D. “Clay Minerals: A Guide to Their x-Ray Identification.” Geological Society of America Special Paper 126. Boulder, Colorado: Geological Society of America, 1970.