Observations from the Analysis of the Gelatin Silver Emulsion Layer of Glass Photographic Inter-Positive Plates from Eadweard Muybridge’s Animal Locomotion Series at the National Museum of American History

ABSTRACT The Photographic History Collection at the Smithsonian’s National Museum of American History houses the largest collection of glass photographic plates from Eadweard Muybridge’s Animal Locomotion series. These images are the immediate predecessor to moving pictures and serve as an invaluable research tool for those seeking to better understand Muybridge’s process and place in the history of photography. As part of a survey of the condition of this collection, analysis of the materials and deterioration products found on these plates was conducted. This paper focuses on observations made during the analysis of the image-bearing gelatin emulsion layer of these objects, as the deterioration and loss of this layer is the most compromising to the identity and significance of the objects themselves. The analysis was performed on image plates and fragments that have become disassociated from their original composite panels. The results of the analyses included: the identification of the gelatin and image forming materials, new information about the photographic processes used in the production of these plates, namely the use of mercury intensification, and significant insights into the various mechanisms of deterioration found on these objects including silver mirroring, water damage, and gelatin cracking, which threaten the long-term stability of this collection.