A platinum print is a monochrome process based on the light sensitivity of iron and platinum salts. The process was patented in 1873 by British inventor William Willis. In 1879, he founded the Platinotype Company, the first firm to market pre-coated papers, which achieved a great deal of commercial success, mainly in England and the United States. However, their popularity was cut short in the 1910s, when platinum prices soared in the lead-up to World War I.
In the platinotype process, a sheet of paper is coated with a mixture of ferric oxalate and potassium chloroplatinate, then dried. The paper is exposed through a negative under bright light. When the image is developed in a bath of potassium oxalate, it dissolves the ferric oxalate and reveals the image by reducing the platinum to a metallic state. Finally, it is cleared with a solution of hydrochloric acid and then washed with water.
The images that result from this process are formed directly in the fibers of the paper, offering a matte appearance and subtle shades of grey that can range all the way to deep black. The tone of a platinum print can be adjusted by using a warm bath to develop them or adding mercury salt to the developing solution. These modifications produce brown or sepia tones.
Thanks to its aesthetic qualities and extreme stability, the platinotype process drew the attention of such major photographers as Stieglitz, Steichen, Strand, and Weston, and appears in the works of Manuel Alvarez-Bravo, Irving Penn, Mary Ellen Mark, Robert Mapplethorpe, and Isabelle Muñoz, among others.
Visual glossary of photographic techniques
© ARCP / Mairie de Paris, 2013