Collaborating institutions
National Endowment for the Humanities | The Catholic University of America
The George Washington University | Library of Congress
Glass at Risk: Simple Tools for Detecting Unstable Glass in 19th-Century Cultural Heritage Collections is a Tier II grant funded by the NEH Preservation and Access Division’s Research and Development Grant Program to create tools that assist in the identification of at-risk glass heritage collection items. It is a collaborative effort between Library of Congress Preservation Research and Testing Division, Library of Congress Music Division, the Vitreous State Laboratory (VSL) at The Catholic University of America and The George Washington University Medical Imaging & Analysis Laboratory.
project background
Caretakers of collections holding 19th-century glass artifacts are not always aware that glass may be an unstable material. Due to the sheer volume of cultural heritage artifacts in this category, especially as produced through 19th-century photography, this represents a potential preservation problem of enormous consequence. For example, cover glasses on early encased photographs often show deterioration, and 19th-century vessel glass is also susceptible. The impetus for this study was in fact a group of rare and exquisite 19th century flutes made by Claude Laurent. In 2014, Carol Lynn Ward-Bamford, Curator of Musical Instruments at the Library of Congress, noticed a disturbing trend: many instruments in this large and outstanding collection of Laurent flutes appeared to have become more opaque over time, a worrying sign of possible deterioration. Ward-Bamford subsequently requested help from the Library’s Preservation Research and Testing Division (PRTD). Spearheaded by Ward-Bamford and Lynn Brostoff, technical analysis of the flutes ensued, and the work eventually expanded into a collaboration with scientists from The Catholic University of America’s Vitreous State Laboratory and George Washington University.
grant goals
The primary objective of this research is to develop a series of simple tools that, when organized into decision trees will assist curators, conservators and scientists alike in the identification of at-risk 19th century glass heritage. The decision trees and accompanying protocols guide users in the examination of glass artifacts, incorporating the use of microscopy and ultraviolet (UV) light, and advancing to more sophisticated, non-invasive spectroscopic and imaging tools, such as X-ray fluorescence (XRF), optical coherence tomography (OCT) and fiber optic reflectance spectroscopy (FORS).
In order to accomplish these goals, as well as conduct a thorough technical study of the fascinating Laurent flutes, the grant research was designed to allow comparison of detailed observations gathered on historical artifacts with data obtained from model glass studies. Technical examination of the 20 glass musical instruments in the Library of Congress collections as well as multiple other institutions worldwide, have been completed using a suite of complementary, non-invasive techniques: light microscopy, XRF, UV fluorescence spectroscopy, FORS, computer X-ray scanning (CT), and optical coherence tomography (OCT). In addition, a limited number of microsamples have been analyzed by scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS), Raman spectroscopy and X-ray diffraction (XRD). Technical analysis of the glass flutes has been supplemented by extensive historical research, since little was known previously about Claude Laurent and his flutes, in order to put these objects into context.
The second type of historical artifacts studied includes photographic glass in American historical society collections, including a selection of materials from the Historical Society of Washington, DC, The George Washington University Library, and the Virginia Museum of History and Culture. The goal of this work is to assess at-risk glass in photographic collections and develop priorities for their preservation. Analysis “on the road” at historical societies utilized a mobile laboratory consisting of a portable XRF, a high resolution digital camera outfitted with a 10x magnification objective, and a home-made, dual wavelength UV light viewing box. In-house examination of historical test samples has also included FORS. These analyses have been supplemented by research into flat glass manufacturing and distribution trends in the 19th century.
Model glass studies, led by collaborators at the Vitreous State Laboratory, have been based on glass made to replicate 19th-century formulations used by Laurent or typical of photographic materials. Artificial aging of the model glasses was conducted at the Library of Congress using steady state conditions; this has been supplemented the Vitreous State Laboratory by Vapor Hydration Testing, an industry standard.