WASHINGTON (AP) _ The Library of Congress, home to the world's biggest collection of books, is working to preserve 1 million of them by getting the acid out of their paper.
More than 150 years ago, papermakers started using chemicals that made their product acidic. The use of wood pulp instead of rags as their basic material made the problem worse, said Kenneth Harris, the library's director of preservation projects. Thus, he has a 30-year plan to deacidify about 8.5 million of the library's 18.7 million books.
A five-year contract the library signed with Preservation Technologies L.P. of suburban Pittsburgh calls for treating 150,000 books in the 12 months that began Nov. 1, at a cost of $2.3 million. The company has already processed 400,000 books for the library.
Its "Bookkeeper" process uses special cylindrical vats. In each vat four books are held spine-to-spine on each of two circular shelves. That way, the books have room to open completely and a deacidifying liquid in the vat can reach every page. The liquid contains particles of magnesium oxide that neutralize the acid and leave a residue to continue the job.
"It's a chalky white, like milk of magnesia," Harris said.
After 25 minutes the liquid is vacuumed out. In two hours the books are dry, ready to be shipped back to Washington. According to the library, "Bookkeeper" adds hundreds of years to the useful life of paper that would otherwise crumble away.
Since the 1970s, books from the United States and other industrialized countries have been printed in increasing numbers on alkaline paper that does not need treatment. But in poor countries, much paper is made the old way. About half of the 200,000 new books the Library of Congress receives each year from throughout the world will be candidates for eventual deacidification.
Preservation Technologies will speed production from year to year. By the time the contract ends in 2005, the company intends to be processing 250,000 books annually, Harris said. By that time, it will also have deacidified at least 5 million sheets of manuscript.
The "mass deacidification" program has focused on Americana _ books and other material dealing with the United States.
Preservation Technologies has developed machinery for processing larger items than books _ newspapers, maps, posters _ and Harris said it would be installed next year in one of the library's buildings on Capitol Hill.
The library will train the company's staff to select books for treatment and ship them to a factory in Cranberry Township, Pa., outside Pittsburgh. The library's staff will maintain quality control over the process and make sure a record of the work on each volume is kept, Harris said.