Relationship between mould growth and recent changes in paper-making

In 2008, documents made of recently manufactured office paper were recovered from a flood in the basement of the Department of Foreign Affairs building in Canberra. The material had been wet for many months but surprisingly showed no mould growth. According to research by the National Archives of Australia (NAA) on 20th century paper quality there is evidence that, in 1994, paper manufacturers in Australia moved away from acidic materials such as alum (aluminium sulphate) in their paper-making processes, replacing them with alkaline chemicals, such as calcium carbonate (CaCO3)1. This has resulted in more alkaline papers being produced, and it is hypothesised that the alkaline environment reduces mould growth on these newer papers.

The aim of this project was to confirm if there is a difference in mould resistance between recent and older papers, and therefore whether the pH pf papers could be used as a factor in triage decisions for the effective storage and salvage of paper collections. Office and newspaper samples from each decade between 1960 and the 2010s were held in high relative humidity to assess the onset and progression of mould growth for each sample. Additional experiments looked at mould growth in agar gel plates containing respectively alum and CaCO3.