Timothy Barrett, hand papermaker and faculty member at the University of Iowa, reported to a group of book conservators June 4 the results of his research project on the quality of early book papers, which will be published soon in The Paper Conservator (order from Institute of Paper Conservation, Leigh Lodge, Leigh, Worcester WR6 5LB, England, or write the author: Timothy Barrett, Associate Research Scientist, School of Art & Art History, University of Iowa, Iowa City, IA 52242). He said the 15th century papers were about one pH point above the worst. The best ones also contained more calcium, magnesium and zinc, while the worst ones had more potassium copper, alumina and sulfur.
A paper based on this research, and scheduled to be given at the American Chemical Society's Cellulose Division meeting in Los Angeles, September 1988, but withdrawn at the last moment, was:
B.H. Kusko and T. Barrett, "Analysis of Historical Paper Specimens by Particle Induced X-ray Emission."
Unfortunately, it does not appear in the published proceedings of that meeting (see Literature section). The abstract says,
Many handmade paper specimens made in Europe between 1400 and 1800 are exquisitely crafted, durable, and free of foxing or discoloration, while other paper specimens are of poorer quality, with foxing, discoloration, and uneven formation throughout the sheet. Particle induced X-ray emission (PIXE) was used to nondestructively determine the sulfur, chlorine, and trace metal content of 133 historical paper specimens, 69 of which were in very good condition and 65 of which were in very poor condition.... foxed spots sometimes contained an order of magnitude more iron than an adjacent clean spot. Sulfur in book paper may have entered from airborne sources as evidenced by decreasing sulfur values from the outer to inner portions of the top, outer, and bottom margins.
Barrett's findings on the pH of early papers are supported by William J. Barrow's investigation of early book papers, reported in Physical and Chemical Properties of Book Papers, 1507-1949 (Permanence/Durability of the Book, VII). W.J. Barrow Research Laboratory, Richmond Va., 1974. Figure 4, "pH of Book Papers (1507-1949)," is reproduced below. It is important to remember that paper declines in pH as it ages, and that the original pH was necessarily higher than it was when Barrow tested it.
"Artificial Aging as a Predictor of Paper's Useful Life," by Helmut Bansa and Hans-H. Hofer, is translation of a German paper that appeared in 1984. It reports the effects of artificial aging an 22 papers produced over the last four centuries, in order to determine which aging conditions appeared to yield the most consistent results and correlate best with natural aging. Most of this 23-page monograph supplement to the Abbey Newsletter is made up of tables and graphs. Some of the data on pH on 18 of the papers is reproduced below, to illustrate how much variation there can be among pH readings obtained by the different methods. (This monograph is available from the Abbey Publications office for $5.00.)
|Paper No.||Surface pH||Cold extract||Hot extract|
1 According to Zellcheming specifications V/17/62, resp. DIN 53124.