CHEMISTRY AND CONSERVATION OF PLATINUM AND PALLADIUM PHOTOGRAPHS
In May 1993, photograph curators adn conservators gathered at the National Gallery of Art in Washington, D.C., to discuss paper base discoloration in prints by Alfred Stieglitz. This Steiglitz Colloquy drew attention to the deterioration of platinum and palladium photographs, the former until recently considered “permanent.” As a first step toward developing a science of conservation specific to platinum and palladium photographs, this study aimed to identify their chemical composition. The goal of chemical characterization of prints is twofold: to enable conservators to care for or repair them and possibly others that are thought to have been made like them, and to illustrate the chemical changes that a print prepared in a certain way will undergo over time. Three interrelated approaches were used to achieve this goal. First, an extensive list of chemicals mentioned by periodicals between 1856 and 1940 for use in platinum and palladium printing and intensification was compiled. Second on the basis of this list, the palladium printing process was re-created in order to determine the effects of different chemicals and printing techniques on the appearance of photographs and so to provide a reference bank with which to identify, using visual information only, how a given print was made. Finally, a method to identify the chemicals used to make a given print was developed using elemental analysis provided by energy dispersive x-ray spectroscopy (EDX) and historical information to infer the compounds the elements could have come from.