Forbes Pigment Labs: Library of Congress

Library of Congress, Preservation lab

The Library of Congress pursues preservation research with the aim to forward the National Preservation Research Agenda, which was developed by the Library's Preservation Directorate in consultation with leading scientific laboratories. This matrix of preservation science projects undertaken by libraries, archives, and museums worldwide illustrates the wide range of preservation research, from scientific and forensic characterization studies to the development of conservation treatments. The diversified labs cover projects on materials research, method development, analytical services and quality assurance. More information on current and paat projects is available at Preservation Scientce.

Analytical Projects

The Preservation Research and Testing Division analyzes the material composition of the Library's collection items to further scholarly research, conservation treatment, and the preservation of the collections. Analytical tests can characterize the chemical composition and condition of a range of materials, including paints, inks, and pigments, coatings, and substrates such as paper, parchment, and papyrus.

Reference collections of known and characterized pigment samples can aid specialists in identifying unknown, unstable, or questioned documents and other works. The Library of Congress holds a collection of pigment samples from Harvard’s Forbes’ Pigment Collection. The Forbes’ Pigment Collection is comprised of over 1000 colorants assembled by the late Edward Waldo Forbes, former Director of the Fogg Art Museum at Harvard University. Although the bulk of the collection resides at Harvard University, nineteen additional laboratories around the world share subsets of the collection, including the Library of Congress. This collection has long been used to provide reference samples to aid in the identification of pigments found in conjunction with collections in libraries, archives and museums.

Forbes Pigment Collection at the Library of Congress

Specialists study media to better understand the nature of documents and other works. Identifying pigments and other media can enable specialists to authenticate questioned documents or identify documents at risk of deterioration from acidic or other problematic media. Such studies can reduce risks to collections while adding value to the knowledge of a document’s provenance and manufacture. Some media (like iron gall ink or verdigris pigments) are acidic and consequently are at greater risk for deterioration and can even contaminate other collections. Characterizing pigments through their respective optical, chemical and physical properties can help specialists “date” documents, since certain pigments were traditionally used at specific times and places. In addition, specialists can estimate the stability, durability and longevity of documents and media made with unstable pigments that might inherently weaken documents.

The purpose of the project is to create an “atlas” of pigments, imaged by a scanning electron microscope (SEM) and matched to their Energy Dispersive X-ray Spectroscopy spectra. This will provide, in conjunction with data from other institutions, a database of known pigment characteristics to aid scholars and preservation specialists in the identification of pigmented media present in the Library’s collections.