A sample survey of the condition of books in the Library of Congress was completed March 28, 1984, by King Research, Inc., of Rockville, Maryland. The survey was commissioned as part of the Library's preparation to operate its recently funded deacidification facility. Information collected included paper strength, paper acidity, liquid content [moisture content?], serviceability of the binding, and age of the book. Refined analyses of the data will continue, but the report makes clear that about three-fourths of the Library's collections will benefit from mass deacidification. (from the LC Information Bulletin for June 4.)
The Library of Congress has 20 million books. If it starts processing them in 1987 and does a half million a year, it should have done the 75% that are acidic by the year 2017. Of course, it will have received more books in the 33-year interval, but if present trends in the use of acid-free and buffered paper continue, fewer of them will need deacidifying. Still, many of the books now in the collection will have become acidic by then.
Books are not the only materials for which the diethyl zinc process is suited. It is the method of preference for colored maps because its effect on colors is negligible. Competition from other formats may keep the books in the Library of Congress from being done as rapidly as they might.
The ideal time to deacidify books and other paper- based materials is before they become weakened, if they cannot survive on their own. The problem then is to identify the materials likely to become brittle, which is not an exact process. Books already brittle are eliminated by the fold test--simply folding a corner back and forth till it breaks--and pH is measured with an indicator (a pH meter is too much trouble if you have thousands of books to do). The pH is our best indicator of future brittleness, though chemists sometimes balk at the idea of using a chemical predictor for a physical characteristic.
Dr. Robert Feller has published and given at AIC meetings several papers dealing with "induction time" in deterioration of certain materials, during which chemical changes go on but physical characteristics do not change noticeably. Finally a chemical change takes place that could be thought of as "the last straw" and physical deterioration is rapid thereafter. His work did not concern paper, but there does appear to be a similar induction time for books--that is, rapid deterioration after a period of relative physical stability. Robert DeCandido reported at the Midwinter meeting of the ALA Preservation of Library Materials Section that his survey of books at the New York Public Library showed a bunching of books on the brittleness dimension: by and large, they could either take over 15 folds, or loss than four. This indicates a rapid decline through the 15-to-four range, and helps to explain the common observation that paper may be very acidic and yet very strong (so far).
The selection criteria for diethyl zinc treatment have not yet been made public by the Library of Congress, and perhaps have not yet even been defined. If the price of treatment is low enough and the price of sorting is high enough, conceivably quite a large proportion of books in the collection could be pot through. The price has been recently estimated at $5.00 per book.
Timestamp: Sunday, 03-Mar-2013 21:34:32 PST
Retrieved: Saturday, 26-May-2018 07:50:35 GMT