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Parchment: Integrated Forensic Investigations

 Background: Parchment is a material used as a substrate for many rare materials found in libraries. Items such as parchment portalan maps found at the Library of Congress have associated pigments and inks that pose preservation problems.

True parchment is an animal skin that has been altered through chemical and physical means to resist putrefacation. It may come from a range of animals, and it has traditionally been produced in different ways in various regions and eras. Such differences may result in disparate aging and reaction characteristics. (Note: The terms "parchment" and "vellum" often are used interchangeably; however the current investigation refers to parchment, which tends to be thicker and less processed than vellum.) Most importantly, parchment is extremely hygroscopic and may dimensionally deform rapidly, radically, and irreversibly in response to changes in relative humidity. Such changes affect not only parchment substrates, but also associated paint or ink media. Certain acidic media can also damage parchment over time, depending on conditions.


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: 31.4Mb / 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 will characterize a wide variety of new parchment control samples (from different animals and made by different processing techniques) using HSI, E-SEM, FT-IR, GC-MS, Raman and other instruments to determine a baseline of optical, chemical and physical properties.

Phase 2: The Library will subject the new parchment control samples to accelerated aging using both conventional dry and humid aging ovens, as well as our E-SEM stage and Weather-o-meter, to simulate the effects of environmental factors of temperature, relative humidity and light on the appearance and durability of parchment.

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.