Physico-chemical characterization and conservation issues of photographs dated between 1890 and 1910

The characterization of the conservation status of photographic materials is usually assessed through visual analysis or optical microscopy. However, a small percentage of these materials cannot be completely characterized by the simple visual-optical inspection and needs a more quantitative investigation. In this contribution, a survey of photographic literature, in particular Italian manuals and periodicals published around 1890–1910, is a primary source. In order to get to a better comprehension of this subject, we adopted a characterization procedure relying both on the analysis of the photographs’ materials and on the knowledge of the techniques and the materials used. Micro-invasive and non-invasive investigations were performed and evaluated in order to understand the chemical and physical degradation processes of photographs from the period around the end of the nineteenth century. We studied two sets of photographs obtained with different techniques but stored under the same environmental conditions. The two sets showed different degradation processes that can be easily attributed to the different photographic techniques used.