The Abbey Newsletter

Volume 12, Number 2
Feb 1988


George M. Cunha, "Mass Deacidification for Libraries," Library Technology Reports 23(3), May-June 1987. P. 359-472. $45 from Library Technology Reports, American Library Association, 50 E. Huron St., Chicago, IL 60611.

Reviewed by Ellen McCrady

This report, commissioned by the American Library Association, makes up the entire 118-page issue, except for a five-page index in the back, and is truly a monumental investigation.

Cunha sets the context for the body of the report with initial chapters on the preservation problem in libraries, with microfilming, deacidification and use of acid-free paper as ways of addressing its past, present and future aspects; the history of paper; and the deterioration of books and paper. The section on the chemistry of deacidification is short and not very detailed, describing only the aqueous magnesium carbonate method, and saying that the methods using calcium or zinc salts are similar; but it gives references to publications that do have the facts. The short historical section describes earlier methods: barium hydroxide (first used 1890 or before); calcium carbonate (Barrow's work in the 1940s); magnesium carbonate prepared from magnesium bicarbonate (Gear, 1957), and from magnesium hydroxide (1978); barium hydroxide in methyl alcohol (Bayne-Cope); the Regnal process for strengthening and deacidifying at the sane time (late 1960s, briefly); spray deacidification with methoxy magnesium methyl carbonate (1970s); the "Viennese process" of aqueous deacidification and strengthening of bound books, then freeze drying them (1984); the Koppers process [reincarnated in August 1987 as the "Bookkeeper Process" and now on the market] which disperses fine particles of the agent through the paper (1981); the Arthur D. Little process, using magnesium alkoxides in critical fluid solvents (1979); ammonia vapors (1960s); cyclohexylamine carbonate (VPD, 1960s); morpholine vapor (1978); diethyl zinc (1970s); and the process being developed by Document Reprocessors, involving a carbonate (1987). Some of the methods are poisonous or dangerous, others safe; some are on the market and others are not; some work and others do not; some require expensive and elaborate plants, while others can be used with very simple facilities; some are suited for mass methods and others are not. More and more libraries, as they complete their preservation surveys and plan their programs, want to include deacidification as a standard treatment option. This is why a guide was needed.

The diethyl zinc process is described in 25 pages, with chemical formulas, costs, procedure, capacity of the new facility to be constructed at Fort Detrick, Maryland, and a recounting of the accidents at earlier test facilities. Zinc oxide is deposited within the paper in this gaseous process, approximately tripling the life of the paper without effecting colors noticeably or causing inks to run. This is the method invented at the Library of Congress, and planned for use on its own collections. It is possible that a way will be found to make it commercially available to other libraries, though they will probably have to use their own or a commercial plant, because the Library of Congress has plans to use its own plant to capacity.

The Wei T'o Process is described in 22 pages, with pictures showing the facility at the Canadian National Archives, which has been in operation for seven years and can do 30 books at a tine. Like the diethyl zinc process, it requires drying the books beforehand. They are immersed in a solution of methoxy magnesium methyl carbonate in alcohol and chlorofluorocarbons for an hour, drained, dried and brought back to room humidity. This results in pH values of 8.5 to 9.5, and an extension of the books' life comparable to that of the diethyl zinc process which, however, leaves the books with a pH close to neutral. The equipment required for the Wei T'o process is pretty complex, but less expensive than that for the diethyl zinc process; because the alcohol causes certain inks to run and adhesives to give way, the books likely to be affected have to be sorted out beforehand. Future improvements are planned for both methods.

A chapter sums up and compares the two methods' costs, chemistry, toxicology, safety, environmental effect, and how well each meets the general criteria for mass deacidification processes. The author hopes that the investigation now being carried out by the Office of Technology Assessment, on the diethyl zinc system's safety and appropriateness, will not be swayed by the zeal of the proponents and opponents of this method.

Appendix A is Robert Parliament's description of the spray deacidification semi-mass production unit at Princeton University. Appendix B, "Techniques for Preserving Newsprint," by Otto Wächter, is substantially the same as his article in Restaurator 8(2/3), 1987, a talk at the 1986 Vienna conference, on aqueous treatment and freeze drying of bound books. Appendix C is Northwestern University's estimate of per-book costs for a Wei T'o mass deacidification facility (under $5, if it is operated at least 60 hours a weak). Peter Sparks was asked to comment on the report before publication, which he does in a long letter at the end. Diethyl zinc, he points out, does not explode; and in a vacuum, which is how it is used, it cannot burn. It does not enter into uncontrolled reactions with the hydroxyl groups on cellulose, as is asserted. Finally, there are two bibliographies, of 118 and 26 items.

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