Paper, the carrier of our written heritage, decays within a relatively short period of time mainly due to its acid content and the influence of air pollution. More than 50% of the records of our libraries and archives are already at risk. Mass deacidification allows this problem to
be counteracted by significantly slowing down the deterioration of paper and thereby prolonging its life span. An overview of all relevant mass deacidification methods is given. As it was found that the 'papersave' method was the most suitable to meet Swiss requirements, a plant using an optimised
version of this method was built and put into service in March 2000. Thanks to this optimisation, not only books and loose sheets but also documents in archival boxes could be mass-deacidified for the first time. Due to the necessity to analyse not only test papers but also original documents,
new non-destructive testing methods had to be developed. Findings of basic investigations regarding treatment effects as well as results of routine quality control turned out to be very satisfactory.
Routine physico-chemical quality control in the papersave swiss process takes place according to defi ned quality standards. Measurements on test books as well as on original material are carried out non-destructively and show homogenous and complete treatment with regard to the accumulated alkali quantity and distribution over the sheet surface. Treatment intensities can be varied and are adapted to the material. The infl uence of treatment intensity on the effi cacy of deacidifi cation was examined. The selected treatment concentrations for the archive and library program leads to an average effi cacy coeffi cient of four. Taking the advantages and disadvantages into consideration, higher or lower treatment intensities are not to be recommended.
The German National Library (Deutsche Nationalbibliothek, DNB) and the Berlin State Library (Staatsbibliothek zu Berlin, Stiftung Preußischer Kulturbesitz, SBB) applied mass deacidification processes using the Papersave™ , the Libertec™ , and the CSC Book Saver™ process to parts of their collections from 1994 (DNB) and from 1998 (SBB) until now. The sustainability of mass deacidification was scientifically evaluated by analysis of 443 deacidified books from both libraries. pH, alkaline reserve and the molecular structure of cellulose were investigated to assess if and to what extent the treatment had improved the overall stability of the paper. This first part of the paper includes results of surface pH measurements and discusses how surface pH, with all its known limitations, can be used as an easily accessible and valuable parameter to determine whether mass deacidification of books was effective. Books treated in the period from 1994 to 2006 were analysed; about 80% of them had a surface pH of ≥7. No distinctive trend by year of deacidification could be discerned except the years 2005 and 2006 which showed a comparatively lower pH. Comparing the pH measured in 2009 with the values measured directly after deacidification, indications of natural re-acidification could be observed in books treated during earlier years. Especially the surface pH measured in older books was found to be slightly lower and more varied.Zusammenfassung/résumé at end of article
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