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Targeted campaign against acid deterioration and decomposition

The mass de-acidification of paper is a much debated topic in the world of archives and libraries. Acid deterioration and decomposition, caused mainly by using inferior-quality paper since the beginning of industrial paper manufacturing around 1850/60, threatens millions of books and kilometers of archived documents. Around the world, an estimated 80% to 90% of the entire stocks of archive and library materials are at risk. Already 10% of this can no longer be used, 30% is affected by decomposition and 40% is threatened.

According to the May 2000 edition of "Der Archivar," the specialist journal for archiving, the mass de-acidification of paper has proven to be a practicable method of preservation since the end of the 1990's. The "Papersave" method previously developed by the company Battelle, and now applied under license at Nitrochemie Wimmis AG, has proven to be extremely successful for this purpose, not only with respect to the results of preservation itself but also with respect to environmental compatibility.

A paper de-acidification plant was commissioned at Nitrochemie Wimmis in April 2000. This plant, which is owned by the Swiss Government, is currently the largest and most modern in the world: Every year between 90 and 120 tons of books and archive materials are de-acidified in the two processing chambers. More than 650 tons of books and archive material have already been de-acidified in this way and saved for future generations.

The largest customers are two state institutions, the Swiss Federal Archives and the Swiss National Library, which currently account for two-thirds of the capacities. And they are more than satisfied with the results produced in Wimmis.

The mass de-acidification of paper can be carried out using various chemical procedures and a variety of chemical substances. Nitrochemie in Wimmis uses magnesium for this purpose: The acids in the paper are neutralized with a magnesium alcoholate, while the magnesium binds the acids, e.g. in the form of a sulfate, and the resulting alcohol is released. Excess magnesium alcoholate is also converted by air humidity and carbon dioxide into a buffer that effectively protects the de-acidified paper against future acid attacks. The chemicals required for this process – hexamethyldisiloxane (HMDO) and a mixture of titanium and magnesium ethanolates (known as Mete 30) – are produced by the Chemicals Division in Aschau for the plant in Wimmis. A considerable amount returns in the form of HMDO condensation and contaminated treatment solution to Aschau where it is converted into useful chemicals again.

All this of course begs the question - why go to such lengths? Why not simply take the easy option and digitalize the affected archive material or even the books and then dispose of the originals? Dozens of digital technology providers in both Germany and Switzerland are outbidding each other to provide a supposedly permanent digital transfer. However, it is not only a question of the price: Chemical mass de-acidification is still by far the cheapest option.

Legal, preservation and cultural aspects also play a role. A great number of legal documents will no longer be valid if they do not exist in paper form. In digital form, and in view of the continuing lack of clarity about forgery protection of such documents, they lose their authenticity and can be used as only working copies, if at all. Chemical de-acidification using this process, particularly thanks to the buffer, guarantees that papers and books will last for decades, possibly even centuries. By contrast, no one knows (yet) how long CDs and DVDs and the data stored on them will last. And even if it is possible to read data carriers after ten or twenty years, it's difficult to locate the suitable hardware in a museum. Plus: The restored first edition of Eduard Mörike's "Mozart auf der Reise nach Prag" (Mozart on the Way to Prague) from 1855 is simply more beautiful than the DVD edition.

Technological development is not standing still: Nitrochemie Wimmis AG is searching intently for a procedure and an effective substance that makes it possible not only to de-acidify paper but also to stabilize papers that have already been damaged by acid. Research and development projects are being performed with the large Swiss customers.

The Bookkeeper procedure is another non-aqueous process on the market. However, in contrast to Papersave, the effective chemicals are suspended rather than dissolved. The CSC-Booksaver procedure developed in 2001 involves mass de-acidification like the Battelle and Bookkeeper procedure just without the use of water.

By contrast with the Battelle and Bookkeeper method, the "Bückeburger procedure" is performed in Neschen (Lower Saxony) on an aqueous basis but can treat only individual sheets of paper. At present, it is not possible to use this method for bound books and documents, as is the case in Wimmis.