Platinotype is a monochrome photographic printing process, based on the light-sensitivity of Ferric Oxalate.

Ferric oxalate is reduced to ferrous oxalate by light. The ferrous oxalate then reacts with platinum (II) (or palladium II) reducing it to basic platinum, which builds up the image.

William Willis discovered the process in 1873 and the first platinum paper reached the market in 1881, produced by the Platinotype Company, a firm founded by Willis in 1879.

When Willis invented the process, platinum was relatively cheap, but it quickly became more costly starting in 1906. In 1907 platinum had become 52 times more expensive than silver. Eastman Kodak and most other producers stopped fabrication of the paper in 1916. Russia controlled 90% of the world platinum supply in World War I and all available platinum was used in the war effort.

Due to the shortage of commercial paper and high cost, photographers experimented with palladium paper and platinum-palladium mixes. Platinum paper has continued in use until the present, interupted only by the world wars.

Characteristics

• An absolutely non-reflective surface of the prints, compared to modern-day glossy prints
• Very delicate, large tonal range
• The prints, not being coated with gelatin, do not exhibit the tendency to curl
• The darkest possible tones in the prints are still lighter than silver-based prints
• Very stable process, platinum prints are far less succeptible to deterioration than silver-based prints

See also: Palladiotype, Photographic processes