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Saving the Written Word:
Mass Deacidification at the Library of Congress

Mass Deacidification Publications Online

mass deacidification process Library Saves Permanently Valuable Books. The Library of Congress, with strong support from the U.S. Congress, has provided leadership in the development and evaluation of mass deacidification processes and their application to valuable books collections and other paper-based items to achieve economies of scale. Through a competitive process, the Library has awarded a series of contracts for mass deacidification to Preservation Technologies, Limited Partnership (PTLP) of Pennsylvania. The company is providing book preservation services to the Library using the firm's Bookkeeper mass deacidification process. The fourth contract, awarded in November 2005, will enable the Library to treat 1,250,000 books and at least 5,000,000 sheets of manuscripts by the end of October 2010. The long-term objective is to treat at least 250,000 books and 1,000,000 manuscripts sheets annually for the next 30 years (the remaining 30 years of the 35-year plan). By the end of 2005, the Library had extended the useful life of 1.4 million books and 3 million sheets of manuscript materials from the national collections.

LC Encourages Others to Mass Deacidify Library & Archival Materials. The Library encourages other institutions to prolong the useful life of invaluable library collections and archival holdings through mass deacidification -- either by negotiating separate agreements or by forming, with other institutions, partnerships that could achieve economies of scale through the treatment of large quantities of materials.

Library “Demonstration Site.” Given the effective operation of its mass deacidification program for books over the past several years, the Library is serving as a demonstration site for managers and technical staffs from other libraries, archives, and cultural institutions. Anyone interested in learning firsthand about administrative and work flow procedures required for mass deacidification programs should contact Kenneth E. Harris, Preservation Projects Director, Preservation Directorate, Library of Congress, LM-G21, Washington, DC 20540-4500. Telephone: (202) 707-1054; Fax: (202) 707-3434; Internet: khar@loc.gov

On-site Contract Work in LC Buildings. Under contract terms, the vendor is providing onsite services in Library of Congress buildings. The company's employees select books for treatment, pack and ship volumes to the deacidification plant, and reshelve books following treatment. After training by Library personnel, the contractor's onsite workers are overseen by a company supervisor, and the Library monitors their progress against contract objectives.

Selection Criteria and Procedures. Deacidification treatment is reserved for books that are acidic and at risk of loss if no action it taken. Due to its role as the national library and the official library of the U.S. Congress, the Library is focusing primarily on selection of “Americana” for early treatment under the mass deacidification program, emphasizing the selection of endangered volumes from collections that are central to the Library's mission. Screening and treatment is being undertaken beginning with the following LC book classes, which have been approved for deacidification processing by Library administrators, preservation managers, and the LC Collections Policy Committee:

Class B
Class C
Class D
Class E
Class F1-975
Class JK
Class KF
Class PN Americana
Class PS
Classes PZ3&4
Class T-TJ
Philosophy, Psychology, Religion (completed)
Genealogy & Biography (completed)
General History (completed)
U.S. History (completed)
U.S. Local History (completed)
U.S. Political Science
U.S. Federal Law
Literary History and Collections
American Literature (completed)
Fiction in English (completed)
Technology, Engineering

Contractor staff working onsite in LC buildings examine each book in collections that have been designated by Library management for deacidification screening. Overly brittle books are left on the shelf.

Books with the following characteristics are generally not considered for deacidification treatment with the Bookkeeper process:

Most books that are deacidified are volumes that are structurally sound enough to be treated in the Bookkeeper vertical treatment cylinders. However, books that have limited binding damage (hinge, joint, head, or tail damage) or are too large for treatment in a Bookkeeper vertical cylinder can be deacidified in other ways by the contractor -- horizontally in manuscript-treatment equipment or sprayed.

Books with the following characteristics are considered good candidates for mass deacidification in the Bookkeeper vertical treatment chambers:

Bound Volumes

Bindings in Good Condition

Text Block in Good Condition

Size Parameters

Quality Controls. The deacidification process, utilizing magnesium oxide (MgO) to neutralize acid in the paper, takes two hours from the time books are placed in the Bookkeeper cylinders until the volumes are ready to be packed for return to their home library. All steps in the process, from selection to reshelving, are monitored to ensure that the intended results are achieved. The Bookkeeper process meets the Library's basic preservation requirements by:

Surrogate test papers that are inserted in 10% of the treated batches of books are tested by both LC and the contractor for alkaline reserve in order to avoid the destructive testing (titration) of actual pages from collection books. At LC's request, the contractor also tests one disposable test book per week to confirm that the process is working properly. Test papers and test books are returned each week to LC for additional laboratory testing.

A further quality control check for alkaline reserve in each batch of books (8 per batch) is made by dividing the weight of the batch into the weight of the MgO used to treat it.

All treated books are marked, like the alkaline books left on the shelf during selection screening, with a white dot on the spine. A Bookkeeper label is also attached inside the back cover of each treated book.

Manuscript Deacidification. Preservation Technologies has developed new equipment that it is using to offer deacidification services for loose manuscript and archival materials. The Library contracted with Preservation Technologies to build and install a horizontal treater and a Bookkeeper spray booth in the Madison Building on Capitol Hill. Installed in August 2002, this equipment is enabling the Library to treat on-site paper-based materials in non-book formats, such as manuscripts, maps, music scores, pamphlets, and posters.

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