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Platinum prints, also called platinotypes, are photographic prints made by a monochrome printing process that provides the greatest tonal range of any printing method using chemical development.

Unlike the silver print process, platinum lies on the paper surface, while silver lies in a gelatin or albumen emulsion that coats the paper. As a result, since no gelatin emulsion is used, the final platinum image is absolutely matte with a deposit of platinum (and/or palladium, its sister element which is also used in most platinum photographs) absorbed slightly into the paper.

Chemistry
The process, which has remained unchanged to this day, is based upon the fact that certain ferric salts can be reduced to the ferrous state when exposed to light rich in ultraviolet radiation, and these ferrous salts can further reduce the platinum salts to metallic platinum. Thus, paper coated with an aqueous mixture of platinum chloroplatinite (and /or sodium palladium chloride) and ferric oxalate, is allowed to dry and the paper then contact printed beneath a negative of the same size as the desired image under sunlight or an ultraviolet light source. The ferric salts become ferrous in proportion to the densities of the negative. The print is then developed in aqueous potassium oxalate which causes the platinum to be reduced to the metallic state. Any light sensitive ferric salts remaining in the paper are dissolved out with very dilute hydrochloric acid and the image which remains consists of pure platinum metal on a substrate of paper fibers, the paper usually being composed of 100% alpha cellulose. Since platinum is extremely inert to any atmospheric pollutant - archivally the print will last as long as the paper upon which it is made.