Mass Deacidification
Background: Some documents are highly susceptible to embrittlement, which can make those documents unusable. Examples include documents made with paper having acidic components. Acid components may come from fiber stock (such as ground wood pulp) or additives (such as bleach or alum rosin size). Once paper is weakened by acid, little can be done to restore original strength. The key to good preservation practice is to prevent the papers with acidic components from becoming weakened by inherent acids. Research has shown that adding alkaline compounds to acidic paper (in a process called deacidification), before embrittlement begins, can extend the life expectancy of these papers. The Library of Congress has a long history of developing a cost-efficient means of mass deacidifying appropriate materials.
Contributing Studies: See the following
The freely available
Adobe
Acrobat Reader is required to view and print the following DF
file:
Library of Congress Technical Specifications
for Mass Deacidification. 2004. [PDF:5.03 Mb / 155 p.]
Technology Helps Library Save its Paper Collection. April 1997.
Mass Deacidification Report: Bookkeeper Process Evaluation. September 1994.
Project Description: Over several decades, the efficacy and cost-effectiveness of various mass deacidification reagents, compounds and procedures were tested by the Library of Congress. This has culminated in the use of a magnesium oxide procedure that has been tested, evaluated, and implemented to treat over a million books and paper sheets a year at the Library of Congress. (For more information, see http://www.loc.gov/preserv/deacid/massdeac.html )
Outcomes:
1. It has been determined that a successful mass deacidification process must:
- raise the pH level of treated paper to a range of 6.8 to 10.4
- achieve a minimum alkaline reserve of 1.5%
- extend the useful life of the test paper (measured by fold endurance after accelerated aging) by over 300%.
2. Selection criteria for books and papers to be mass deacidified have been determined.
3. Tracking systems have been developed.
4. Quality Control procedures have been developed.
Update and Images: Through a competitive process, the Library negotiated a fourth contract for mass deacidification in 2005 with Preservation Technologies, Limited Partnership (PTLP) of Pennsylvania. The company is providing book and manuscript preservation services to the Library using the firm's Bookkeeper mass deacidification process. The first contract, in 1995-96, was an R&D process enhancement initiative that enabled the Library to deacidify real Library books for the first time and to resolve book selection, shipping, and quality control details of the deacidification program.
The images below show how books are mounted in vertical treatment cylinders and manuscripts in horizontal cylinders, where magnesium oxide is deposited to neutralize acids in the paper.
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