Improved Traditional Paper Accelerated Aging Tests
Background: In 1994, the American Society for Testing and Materials (ASTM) and its Institute for Standards Research (ISR) began a $4 million, five-year research program into the aging of printing and writing papers. The goals of the program were to develop new accelerated aging test methods and to demonstrate that the degradative chemistry and physics caused by the test methods were essentially the same as what occurs during natural aging. Five laboratories conducted this work, which addressed elevated temperature, elevated light flux, and elevated concentration of common atmospheric pollutant gases. The LC Preservation Research and Testing Division performed research involving elevated temperature (at constant paper moisture content).
Contributing Studies: Shahani, C.J.; Lee, S.B.; Hengemihle, F.H.; Harrison, G; Song, P.; Sierra, M.L.; Ryan, C.C.; Weberg, N. Accelerated aging of paper: I: Chemical analysis of degradation products, II: Application of Arrhenius relationship, III: Proposal for a new accelerated aging test. Preservation Research and Testing Division, Library of Congress, Washington, DC; June 2000. Available from the American Society for Testing and Materials (ASTM).
Project Description: The research performed by the LC involved Arrhenius-type studies of six papers that modeled a range of paper stability: a highly stable cotton-fiber paper, both acidic and alkaline; a medium-stability bleached northern softwood Kraft paper, both acidic and alkaline; and a low-stability stone ground wood paper, both acidic and alkaline. The LC studied free-hung sheets, stacks of sheets in humid ovens, and sheets that were conditioned at 23ºC (73ºF) and 50% RH and then heat-aged in hermetically sealed glass tubes. The LC also incorporated the use of two chromatographic methods to obtain chemical "fingerprints" of the organic compounds formed as the result of the different aging protocols. The LC compared the chemical fingerprints from the accelerated aging studies to the chemical fingerprints from old (naturally aged) papers.
Outcomes/Findings: There were several important findings from this research:
- Arrhenius relationships show no detectable changes in the reaction mechanisms over the high temperature ranges studied. However, as supported by results from the Canadian Conservation Institute (CCI), aging data obtained at high temperatures cannot be extrapolated accurately to ambient (room temperature) conditions.
- Chemical analyses reveal that small organic acids form spontaneously in the aging of all cellulosic papers, including highly stable cotton papers and alkaline papers, even at room temperature.
- Chemical fingerprints of degradation products formed as a result of natural vs. accelerated aging are similar, with the greatest similarity being between naturally aged papers and papers conditioned at 23ºC and 50% RH and then heat-aged within airtight glass tubes.
- Data from Arrhenius plots and chemical analyses show that accelerated aging of paper samples conditioned at 23 and 50% RH, and then aged inside an airtight glass enclosure at an elevated temperature, models natural aging better than aging either as loose sheets (normal practice) or in book-like stacks.
Support: Library of Congress Library Services
Acknowledgements: Library of Congress and the staff of the Preservation Directorate
Update and Images:
March 2007: Results of both research efforts were presented at the Institute of Conservation (ICON) 5th IPC International Conference in Edinburgh.
April 2008: Case studies of manuscript treatments guided by the flowcharts were presented at the American Institute for Conservation (AIC) 34th annual meeting in Denver, CO, and will appear in the associated postprints.
