G E H L I M A G I N G

Alternative Photo Processes

Cyanotype is a non-silver process invented by Sir John Herschel in the 1840s. A mixture of ferric ammonium citrate and potassium ferricyanide is coated on sized paper and allowed to dry. It is contact printed using ultraviolet light and oxidized in a hydrogen peroxide solution. This is the blueprint process which was used for many years. The image tends to fade over time, especially when exposed to sunlight.