Alternative Process : Cyanotype

Brian Young

In 1842 Sir John Herschel invented the cyanotype in 1842, it is the first permanent non-silver process. The 2 chemicals used are potassium ferricyanide and ferric ammonium citrate green, which you brush onto the paper. Then you expose it to the negative and process it in the sun. The picture really shows up when you wash it in cold water. The cyanotype became widely used in the late nineteenth century for engineering (blueprints).