The Library of Congress, with strong support from the U.S. Congress, has provided leadership in the development and evaluation of mass deacidification processes. The Library's 30-year initiative in mass deacidification began in 2001 and aims to extend the life and utility of at-risk paper-based materials in the Library of Congress for continued access. Mass deacidification is an economic approach to stabilizing acidic books and manuscripts through large-scale treatments.
Mass Deacidification Program
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 book 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 fifth contract was awarded in January 2011By the end of fiscal year 2013, the Library had extended the useful life of 3.78 million volumes and over 10 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 Jeanne M. Drewes, Chief, Binding and Collections Care Division, Preservation Directorate, Library of Congress, LM-G21, Washington, DC 20540-4520. Telephone: (202) 707-5330; Fax: (202) 707-3434; Internet: firstname.lastname@example.org
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 volumes that are acidic and at risk of loss if no action is taken. Due to its role as the national library and the official library of the U.S. Congress, the Library was focused 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 has been undertaken and to date the following LC book classes, which have been approved for deacidification processing by Library administrators, preservation managers, and the LC Collections Policy Committee:
Retrospective Collections ('completed' or in process):
- Class A — General Works (selected areas)
- Class B — Philosophy, Psychology, Religion (completed)
- Class C — Genealogy & Biography (completed)
- Class D — General History (completed)
- Class E — U.S. History (completed)
- Class F1-975 — U.S. Local History (completed)
- Class G — Geography; Anthropology (completed)
- Class H — HJ— Social Sciences (completed)
- Class HM—HX Social Sciences (continuing)
- Class J — Political Science (continuing)
- Class K — Law (continuing)
- Class KF — U.S. Federal Law (completed)
- Class L — Education (completed)
- Class M — Music (continuing)
- Class P — Language and Literature (completed)
- Class Q — Science (continuing)
- Class R — Medicine (selected areas)
- Class S — Agriculture (selected areas)
- Class T-TX — Technology, Engineering
- Class U-V — Military and Naval Science
- Class Z — Bibliography (selected areas)
Prospective Collections (new acquisitions, in process):
- Various Classes — Ongoing, daily screening through Binding and Cataloging work flows
Books that are not treated. 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:
- Text paper is alkaline or permanent (these books are marked with a white dot on the spine, as are books that are deacidified; in both cases, this mark indicates longevity of the text block)
- Text paper is coated or super-calendered (coated paper is not a high priority for deacidification, due to its alkaline coating) Many art books are on coated paper so for this reason the N class is not part of this program.
- Title is already available in (or scheduled for) microform or digital format, or it is a candidate for future reformatting due to advanced embrittlement of the paper
- Duplicates of a given imprint of a specific title (only one copy of any given imprint is treated)
Most books that are deacidified are volumes that are structurally sound enough to be treated in the Bookkeeper vertical treatment cylinders. Books that have binding damage are given conservation treatment in-house and then routed for deacidification treatment. Materials that are too large for treatment in a Bookkeeper vertical cylinder can be deacidified in other ways by the contractor — e.g., horizontally in manuscript-treatment equipment or sprayed.
Good Candidates for Treatment. Books with the following characteristics are considered good candidates for mass deacidification in the Bookkeeper vertical treatment chambers:
- Hardbound volumes generally treat better; however,
- softbound volumes if they are in good condition and structurally sound can be treated (it is critical to determine whether the paper is too brittle to withstand treatment and whether the binding adhesive is too degraded to support the text)
- Plasticized covers will not fully absorb the magnesium oxide and will require wiping off by contractor staff after treatment
Bindings in Good Condition
- No detached covers (boards)
- Leather covers with red rot are OK
- Minor damages (e.g., head cap, head, or tail, as well as minor spine tears and minor hinge or joint damage) are acceptable
Text Block in Good Condition
- No loose or torn pages
- Leaves not overly brittle
- No “blocking” (pages stuck together)
- Large and heavy books and oversize unbound materials can be treated in Bookkeeper chambers or sprayed.
Quality Controls. The deacidification process, utilizing magnesium oxide (MgO) to neutralize acid in the paper, takes 1½ 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:
- raising the pH level of treated paper to the acceptable range of 6.8 to 10.4pH
- achieving an alkaline reserve of 1% to 3%
- extending the useful life of paper (measured by fold endurance after accelerated aging) by over 300%.
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 treats 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. Currently, all materials treated are documented as treated in the Intergrated Library System (ILS).
Preservation Technologies 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 of a certain size.