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The case study

Microbial deterioration is a common problem in photographic collections, and has been considered a major cause of deterioration. However, few studies have been carried out on this topic. Indeed, most of the literature is concerned with biodeterioration of archival documents in general, and this includes both micro and macroorganisms. The environmental factors that promote this type of deterioration are well known and most of the published information is about prevention and control. There have been no detailed studies on the interactions between microorganisms, environment and the composition of photographic material. This study is focused on microbial deterioration of gelatin emulsion photographs, especially related to fungi. It was part of a global study of three collections in Lisbon, Portugal. The first part is a quantitative study on the microbial contamination of the Horácio Novais collection. The second is about induced contamination experiments of gelatin emulsion photographs. At the end these data will be analyzed taking into account the hypothesis that color materials are more susceptible to microbial deterioration than black and white ones. This hypothesis is based on the observations of several professionals working with photograph collections who report that, at least in plastic base supports (negatives and slides), color materials are frequently more contaminated than the black and white ones.