Mass de-acidification

The German National Library’s collection is under threat from one source of damage in particular, namely the accelerated ageing of cellulose, the basic component of paper, under the influence of acid. The papers from the period between around 1850 to 1990 are affected by this phenomenon to varying degrees, depending on the manufacturing process involved. Damages such as brittleness and yellowing therefore occur to varying degrees of intensity.

For this reason, we have been outsourcing the de-acidification of our collections since 1994. Using a so-called mass de-acidification process, the acid in the paper is neutralised and an alkaline reserve introduced. In this way, several tons of library holdings are de-acidified by a contractor every year, in combination with internal quality controls.

In the “Sustainability of mass de-acidification of library holdings” project, we evaluated the sustainability of mass de-acidification via scientific analyses. The project was based around the holdings of the German National Library in Leipzig and the Berlin State Library – Prussian Cultural Heritage, which were de-acidified between 1994 and 2006 and between 1998 and 2006. The chemical analyses were performed by the Department of Chemistry at the University of Natural Resources and Life Sciences, Vienna. Alongside the pH-value and alkaline reserve, an artificial ageing process was used to examine the long-term behaviour of the de-acidified papers. This yielded the important insight that the effect of de-acidification is all the more effective the less damaged the paper is at the start of the treatment. In a best-case scenario, the paper’s degradation can be slowed down by a factor of three using de-acidification – however, it cannot be be stopped entirely.

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