JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. ABSTRACT-The Stieglitz Colloquy in May 1993 drew attention to the deterioration of platinum and palladium photographs, even though the former is considered to be among the most "permanent" photographic techniques. The chemical composition of the two types of photographs is clarified to aid the conservator in distinguishing the prints and determining the types of deterioration they might be subjected to in the future. The prints are chemically characterized by three means: by searching the available literature for references to processes, beginning in the 1850s; by re-creating the processes according to the recipes; and by developing a method using energy dispersive x-ray spectroscopy to carry out elemental analysis of the metals used in the processes, thus allowing the chemical compounds that might have originally supplied the raw materials for the processes to be inferred. 1856; Photographic Notes 1856; Gwenthlian 1859). Old sources often use the terms "toner" and "intensifier" interchangeably. Platinum and palladium treatment of iron, mercury, silver, and uranium prints is more properly viewed as intensification. William Willis is widely credited with having created the platinum printing process. However, the first mention in the literature of a sensitizer based on platinum cites the experiments of a Mr. Merget, in which paper is coated with platinic acid, ferric JAIC 34(1995):11-32 This content downloaded from 195.34.79.207 on Tue, 10 Jun 2014 21:57:32 PM All use subject to JSTOR Terms and Conditions 12 ADAM GOTTLIEBchloride, and tartaric acid, then exposed, and developed using mercury vapor (British ournal of Photography 1873; Abney and Clark 1898). From this departure point, William Willis designed and patented the first successful platinum printing process using a ferric oxalatepotassium tetrachloroplatinite sensitizer. The oxidation-reduction chemistry of these two ingredients, whereby iron is reduced upon exposure to ultraviolet light, then oxidized by a developer with concomitant reduction of platinum, and finally cleared using hydrochloric acid, remains the basis of platinum and palladium printing. The terms "fixing" and "clearing" are used interchangeably in old and current sources alike. "Clearing" is used to distinguish platinum and palladium processes from silver printing. Whereas many firms, including Willis Platinotype Company, mass-produced platinum printing papers, the process survives today as it was created, with hand-coated papers.Features of Willis's initial process that have since been changed include the use of the oxidizing agents lead nitrate and silver nitrate in the sensitizer to prevent ferric oxalate from being reduced prior to exposure and to produc...