Overview of fungal isolates on heritage collections of photographic materials and their biological potency

Despite controlled relative humidity in archives and private collections, fungi are a
widespread cause of biodeterioration of cinematographic films and historic
photographs, which represent a significant cultural and historic loss to society.
Photographic emulsions and coatings are organic and hygroscopic in nature and
represent a good and easily accessible source of nutrients. Because archives hold
whole stacks of these materials, they subsequently contain more fungi in comparison
to other enclosed spaces. This in turn generates a need for a systematic
microbiological evaluation of fungi isolated from photographic documents in order to
pinpoint the potentially biodeteriorative fungal species and increase awareness and
control readiness when these species are encountered. With this aim, we have
decided to collect data regarding fungal isolates and their biological potency from the
following originating materials: gelatin cellulose triacetate or cellulose nitrate films,
albumen or gelatin paper photographs, cellulose nitrate negative films, gelatin glass
plate negatives and positive paper prints. In addition, the most efficient biotic degraders
of gelatin binder are presented and the degradation of cellulose based supports as well
as the occurring microbial interactions and the impact of inhibitory silver salts are
reviewed. Lastly, based on the origins of fungal contamination and the occurrence of
fungi related to allergenic and toxicogenic diseases, prevention and control measures
are suggested.