Volume 11, Number 6
Aug 1987

Carbonate Content of Certain Archival Papers

Three years ago, the Editor co-authored and published a study of the pH of new books at Columbia University (AN, Feb. 1984, p. 2). Part of that study involved a test for the presence of alkaline reserve or buffering in the book paper. This test was performed on tiny samples punched from the pages and from other papers known or believed to be either alkaline or acidic, as a control. It involved moistening the sample with a drop of acid (6N HCl) and observing under magnification the presence or absence of effervescence--a modification of the qualitative test suggested in ANSI/ASTM D 3290-76, "Standard Specification for Bond and Ledger Paper for Permanent Records." The majority of papers with a pH above 6.7 did effervesce--but inexplicably, some well-known permanent papers in the control group did not. Among them were the following papers:

1. Mohawk Superfine
2. Howard Perma-Dur (same thing as Howard Permalife)
3. Howard Permalife (samples from 2 or 3 batches)
4. Standard Permalife, white and cream. (Standard went out of business around 1976.)
5. Archive Long-Life Test from Guard Bridge Paper Co., the paper Barrow chose in 1967 for the National Union Catalog ("The Mansell Set")

The paper chemists at Mohawk and Howard, when contacted by telephone, said their papers were definitely buffered, but could not explain the absence of effervescence.

In an effort to clear up the mystery, analyses of these same control papers were requested in 1985 and 1987 from two paper testing labs. One lab tested three papers for % carbonate, and found wide variation between determinations or samples, which suggests that the carbonate is not uniformly distributed in the sheet.

These results were forwarded by Maurice Douek head of the Analytical Services Section at the Pulp and Paper Research Institute (PPRI) of Canada, who observes, "It is possible that on the samples that you tested, the amount of carbonate was too low to be detected by adding acid."

The other lab analyzed two samples of Paper #3 (purchased in 1983 and 1984), two of Paper #4 (white and cream, manufactured before 1976) and one of Paper #5 (a sample received about 1980), to detect the presence and relative amounts of calcium. For comparison, they also analyzed one sample of Ecusta Waylite, the paper on which this Newsletter

is printed, which effervesces vigorously in contact with acid, and which is about 20% carbonate by weight. The method used was energy dispersive X-ray analysis.

All of the papers contained substantial amounts of calcium. It is not known whether the Permalife analyzed by the first lab came from the same batch as either of the samples analyzed by the second. One can see, however, that the amount of calcium in the different samples varies quite a bit, even within the same brand of paper (Permalife).

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Conclusions

1. Because the carbonate may not be evenly distributed, the average of several large samples should be taken if an accurate figure is desired. This is true no matter what testing method is used.
2. The effervescence-in-acid method does, however, appear to discriminate between papers containing less than about 3% carbonate, and those containing a larger percentage. There is still some question whether other factors, such as type or degree of sizing, influence results. Therefore, it may be useful for finding the minimum percentage of the total number of books that are definitely buffered. The results should be stated something like this: "At least 7 of book papers tested are buffered."
3. Because pH and carbonate content are not the only factors in permanence, and because no aging studies were done on the samples, no conclusions can be drawn about the relative permanence of the papers tested.
4. Because the samples were arbitrarily selected and were stored under unrecorded conditions during the years since their receipt, they can not be taken as representative of the papers produced today by the same companies.