Mass Deacidification - History of Deacidification Research and Process Development

History of Deacidification Research and Process Development

Mass deacidification - along with microfilm and lamination - was developed during the early- and mid-20th century as a response to the chemical process of hydrolysis by which the fibers that constitute paper, providing its structure and strength, have their bonds broken, resulting in paper that becomes increasingly brittle over time. Environmental pollutants can react with paper to form acids that promote oxidation, creating more acid as a by-product, which results in a positive feedback loop of autocatalytic destruction. Supported in part by grants from the Council on Library Resources, William J. Barrow conducted research into paper decay and found that no more than three percent of the books published between 1900 and 1949 would survive more than fifty years. In response to this, a Standing Committee on the Preservation of Research Library Materials was formed by the Association of Research Libraries (ARL) in 1960.

Barrow also invented an aqueous process to neutralize acid in paper while depositing an alkaline buffer that would retard the rate of decay. In addition to Barrow’s original method, both non-aqueous - employing organic solvents - and vaporous - the Library of Congress’ DEZ (diethyl zinc) treatment - methods of achieving the same results have been researched in an attempt to reduce time, labor, and cost requirements.

One technique proposed was to place books in an evacuated chamber, then introduce diethylzinc (DEZ). In theory, the diethyl zinc reacts with acidic residues in the paper, leaving an alkaline residue that would protect the paper against further degradation. In practice, the heating required to remove trace water from the books before reaction (DEZ reacts violently with water) caused an accelerated degradation of the paper, and a range of other chemical reactions between DEZ and other components of the book (glues, bindings) caused further damage and the production of unpleasant smells. Regardless, in the 1980s, a pilot plant for mass deacidification using this process was constructed by NASA and was tested on books provided by the Library of Congress. However, it was discovered in 1986 that the DEZ had not been removed in one of the deacidification runs and was pooled in the bottom of the chamber, and probably remained within some of the plumbing. DEZ is violently flammable when it comes in contact with either oxygen or water vapor, so the vacuum chamber could not be opened to remove the books within. Eventually, explosives were used to rupture the suspect plumbing; suspicions of the presence of residual DEZ were confirmed by the subsequent fire that destroyed the plant. In his book Double Fold, Nicholson Baker discusses the failure of the NASA program at great length.

The chemical company Akzo made later attempts at refining the process; though the risks of fire and explosions were reduced by better process design, damage and odours remained a problem. In the end, Akzo decided the process was not a viable commercial proposition, and shut down their research at the end of 1994.