Background: Parchment is a material found in many special collections in libraries, archives, historical societies, and museums. Western maps, deeds and other important documents, medieval manuscripts, and bindings are often made of parchment. True parchment is animal skin that has been altered (but not tanned) through chemical and physical means to resist putrefaction. It can be made from different animals (but is usually goat, cattle, or sheep) and traditionally has been produced in different ways in various regions and times. These differences may result in disparate aging and reaction characteristics. Most important to the Library's parchment research is the extremely hygroscopic nature of parchment, which can cause it to deform rapidly, radically, and irreversibly in response to changes in relative humidity. Such changes affect not only the parchment material, but the materials in contact with the parchment -- e.g.: paint or ink media; the book pages inside the parchment binding. In addition, certain acidic paints and inks can also damage parchment over time and these chemical processes appear to be affected by environmental conditions as well.
Contributing Studies:
Hansen, E. F., S. Lee, and H. Sobel. "The Effects of Relative Humidity on Some Physical Properties of Modern Vellum: Implications for the Optimum Relative Humidity for the Display and Storage of Parchment." Journal of the American Institute for Conservation 31, no. 3 (1992): 325-342.
Quandt, A., and W. Newman. "Parchment Treatments." [PDF: 31.4 MB / 144 p.] Paper Conservation Catalog, Chapter 18. Washington, D.C: American Institute for Conservation Book and Paper Group. 1994.
Project Description: The overarching goal of the Library’s current forensic project for parchment is to understand more precisely how and under what conditions parchment ages, in order to determine environmental parameters that might slow the aging process. The project has three phases.
Phase 1: The Library has begun characterizing a wide variety of new parchment control samples (from different animals and made by different processing techniques) for baseline properties using a range of instrumentation; including hyperspectral imaging (his), environmental scanning electron microscopy (E-SEM), Fourier transform infrared spectroscopy (FT-IR), gas chromatography mass spectrometry (GC-MS), Raman spectroscopy and other instruments to determine a baseline of optical, chemical and physical properties.
Phase 2: The Preservation Research and Testing Division has begun to subject the new parchment control samples to accelerated aging creating a series of naturally and accelerated aged parchment samples in a matrix of different environmental conditions. The environments include temperature, relative humidity, visible and ultra-violet light, and various treatments. This will enable a better understanding of the degradation mechanisms that occur under different environmental conditions and simulate the effects of environmental factors of temperature, relative humidity and light on the appearance and durability of parchment. The aged samples will then be re-examined with the range of instrumental techniques to progressively track changes due to the various conditions.
Phase 3: The Library will re-characterize the accelerated aged parchment control samples using the same imaging techniques and other instruments to identify optical, chemical and physical changes in order to develop markers for such changes and help the Library determine the best way to set environmental parameters to slow such changes. For example, HSI allows detection of changes due to environment long before these are detectable by the un-aided eye.
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