The process for making platinum prints was invented in 1873 by William Willis. The process depends on the light sensitivity of iron salts to create an image. Chemical reactions exploited during developing, however, dissolve out the iron salts and replace them with platinum.

Platinum images are among the most permanent graphic images in any medium. This process involves mixing small amounts of platinum and palladium with a light sensitive solution containing ferric oxalate. This mixture can then be spread onto the surface and is left to dry. After the emulsion is dried, the paper is placed in contact with a negative the same size as the final print and is exposed to ultra-violet light or sun light. Finally the exposed print is processed. Then it is cleared by washing out the ferric oxalate with several successive baths of hydrochloric acid. It’s finished by washing in water and dried.