An analytical study on an early twentieth-century Italian photographs collection by means of microscopic and spectroscopic techniques

Italian photographs, dated between 1890 and 1930, on simple or treated paper support, chosen to be faithful to Italian photographic tradition of those times, were studied with non-invasive techniques. A first investigation by optical microscopy in reflected light put in evidence the surface peculiarity of each different photo types, characteristics and deterioration of the fibres and vegetable biodeteriogens morphology. The study of coatings and supports composition, carried out with Fourier transform infrared micro-spectroscopy in attenuated total reflectance, allowed to recognize the presence of proteinaceous binder and inorganic salts. Moreover, stereomicroscopy, optical microscopy (in reflected and transmitted light) and scanning electron microscope were used for more detailed study of biodeterioration phenomenon. These instrumental techniques have been useful to evaluate cause of chromatic differences on the surface, allowing the identification of different fungi species, and, particularly, a class of them never documented on photographic materials has been detected. Materials identification, deterioration knowledge and formulation of hypothesis on the causes of deterioration are of primary importance to act the better choice for adequate preservation and conservation process. This study shows how non-invasive techniques are completely applicable on photographic materials, field in which diagnostic analyses are still not fully overworked.