Cyanotypes are one of the oldest photographic printing processes. The cyanotype process was invented in 1842 by astronomer and scientist, John Herschel. The process has been used in botany to document plants, and to create copies of drawings and blueprints.

Cyanotypes are created when ferric ammonium citrate or ferric ammonium oxalate is mixed with potassium ferricyanide and becomes sensitive to UV light. After exposure to UV light, the stunning color of Prussian blue is revealed.