The analysis of art objects is a demanding discipline. Materials used to create art in the past are not pure, well-defined chemical compounds that lend themselves to simple industrial analysis. Typically colorful inorganic pigments were extracted from raw minerals that had different compositions or impurities based on their place of origin. Organic materials used to make dyes, binding media for paintings, and coatings and varnishes were obtained by processing natural material ranging from fresh flowers to animal bones and skins. These materials were of low purity and were often mixed, forming concoctions that offer scientists numerous analytical challenges.

	Samples of commercial pigments, raw materials used in the production of pigments, various types of artist paints, and draw down samples of paints for natural aging. Photo: Dusan Stulik.

In the course of their work, scientists at the Getty Conservation Institute (GCI) have analyzed art objects from a wide range of sources around the world. These objects not only present difficulty in identifying their less-than-pure components; they also display deterioration, damage, and aging, which further complicate the analytical task. In fact, a thorough analysis is almost impossible without the existence of well-characterized standards or reference materials.

The GCI Reference Collection, established in the early 1990s, is a repository of reference materials for use in the analysis of art objects. The collection supports not only various research and service tasks of the GCI Science department, but also the GCI Field Projects department and the conservation laboratories of the J. Paul Getty Museum.

	Art Kaplan, coordinator of the GCI Reference Collection, cataloging samples in the reference collection database. The database currently has over 9,000 samples. Photo: Dusan Stulik.

The collection began with several tubes of paint and a few bottles of raw materials typically used to make paints: pigments, resins, gums, oils, and waxes. Since this simple beginning, the collection has grown into more than nine thousand materials, which are housed in a dedicated, environmentally controlled room.

The collection contains a wide variety of inorganic and organic pigments and dyes; raw plant and mineral samples; well-characterized wood samples; stone samples; drying oils; natural and synthetic resins; waxes; prepared media; varnishes; and different protein-based materials, among other things. Examples of various photographic processes and photographic materials from the era of chemical photography are also part of the collection.

	The GCI Reference Collection, stored under monitored and recorded environmental conditions. Photo: Art Kaplan.

The collection continues to grow through purchases by the GCI, as well as through donations by individuals and institutions. Among the acquisitions are samples from the Forbes Collection of the Materials of the Artist and the Gettens Collection of Aged Pigments and Media, obtained from the Harvard University Art Museums. Samples donated by individuals include materials from the studio and darkrooms of portrait photographer Carl W. Knight, donated to the GCI by Paul Christopher of Santa Paula.

The GCI Reference Collection Database

The collection is catalogued using database software that allows searching for information, about specific samples or the collection as a whole. Each sample has a unique record, with information ranging from chemical composition to manufacturer and geographic origin to experiments that have been performed on the sample. In addition, links are provided to analytical data obtained from instruments in the GCI Science department. This valuable resource for researchers at the Getty ultimately will be shared with conservators throughout the world.

	Binding media, including natural oils, glues, waxes, and eggs. The collection also contains a wide selection of raw materials used to produce binding media. Photo: Art Kaplan.
	Samples of various woods, textiles, textile fibers, and fabric supports for paintings, together with examples of artist brushes made from different types of animal hairs. Photo: Dusan Stulik.
	Collection of photographic materials containing well-defined and well-described samples of different historical photographic processes, with their analytical signatures. The collection also contains a large selection of sample books and commercial photographic materials, as well as different types of photographic toners and coatings. Photo: Dusan Stulik.
	Stone and building materials, ranging from decorative marbles to samples from different field projects conducted by the GCI. Photo: Art Kaplan.
	Collection of binary mixtures of binding media, an important tool in developing various analytical methodologies for analysis of artifacts. More than 900 samples were prepared using combinations of different binding media in concentrations ranging from 0.1%–99.9%. To record the effect of pigment presence, binding media mixtures were combined with pigments of different reactivity. Photo: Dusan Stulik.

	Analysis data screen showing which data has been collected for each sample. The ultimate goal is to obtain a full set of analytical data for each sample in the collection, which can then be viewed from any computer that has access to the reference collection database, no longer requiring individuals to look through old sets of data or back to an instrument in order to view the results.
	High resolution digital photos are taken of all samples, along with a color test patch.  This allows any user to calibrate their monitor in order to accurately view the sample in its "true" colors. Photo: Dusan Stulik.
Image of an azurite pigment sample, PIG15451, obtained using darkfield and brightfield polarizing light microscopy.
	Environmental scanning electron microscopy (ESEM) image of an azurite pigment sample, PIG15451, showing where individual spectra were obtained.The ESEM allows the viewing of samples at a magnification much higher than what is possible with conventional light microscopy technniques.
Eneregy Dispersive X-ray spectra obtained using the ESEM of an azurite sample, PIG15451, showing the presence of aluminum, silicon, potassium, iron, and copper.  The technique gives information on the inorganic componenets in a given sample.
	Fourier Transfor Infrared Spectrum (FTIR) obtained for an azurite sample, PIG15451.  FTIR provides information on organic molecules and functional groups found within a sample.
	X-ray diffractogram of an azurite pigment sample, PIG15451.  X-ray diffraction is a technique that provides information on the crystalline structure of a sample.  Each diffractogram is unique to each crystalline solid and can be used as a fingerprint for the identification of various materials.

Last updated: May 2006