A nonsilver photographic printing paper that used sodium or potassium tetrachloroplatinite as the light sensitive compound. Platinum was first used for photography in 1856 as an intensifier for silver prints. In 1873, William Willis patented the process for platinum printing in which paper is coated with a mixture of oxalic acid and potassium chloroplatinate. The iron is reduced with exposure to light then oxidized with a potassium oxalate developing solution with the concurrent reduction of fine-grain platinum. The prints are then fixed with a clearing solution containing ammonium hydroxide ammonium chloride, oxalic acid, sodium chloride, and sodium hyposulfite. Platinum prints have a clear gray tonality, fine black details and a matte surface. They were discontinued by World War I due to the extremely high price of the metal.
Synonyms and Related Terms
platinotype; platinum print; potassium chloroplatinite paper
A.Gottlieb "Chemistry and Conservation of Platinum and Palladium Photographs" JAIC 34:11-32, 1995.
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- The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998