Mass Deacidification
Aiming at prolonging the life of materials printed on acid paper, about 1,000 extra copies of Japanese books in the NDL collection were experimentally deacidified by the gaseous phase DAE (dry ammonia ethylene oxide) method at the facilities of a private company, Nippon Filing Co., Ltd., from March 5 through 16, 1999.
It is said that the treatment slows the deterioration of materials by a factor of three to five times. NDL sample materials, which were processed simultaneously with the spare copies mentioned above, showed that after treatment the average pH value of 4.56 rose to 9.76. A tearing resistance test using the company's samples also showed that after the treatment the paper lasted five to seven times longer. So this method was proven to be effective for the mass deacidification of acid paper, though a little smell remained right after the treatment and the material got slightly yellowish.
The mandate of the NDL is to preserve as cultural heritage books, magazines, and other original materials, particularly those published in Japan, for as long as possible and to hand them down to future generations. Current deacidification methods are known to be effective for the long-term preservation of original materials produced on acid paper. Certain points, however, remain to be resolved. In addition, the number of materials in the library that fall into this category is extensive, and the costs of deacidification are enormous. Because some items on acid paper are showing noticeable signs of deterioration, medium- and long-range plans must be made to deal with them.