Cyanotype is a photographic printing process that gives a cyan-blue print. The English scientist and astronomer Sir John Herschel discovered this procedure in 1842. It was Anna Atkins who brought this to photography. Unlike photographs set in silver, like in black and white photography, cyanotypes are using a solution of iron compounds.
Cyanotype is a very simple process. It involves treating a surface with iron salts that reacts to UV light.
The cyanotype is made up of two solutions:
Solution A: 25 grams Ferric ammonium citrate (green) and 100 ml. water.
Solution B: 10 grams Potassium ferricyanide and 100 ml. water.
A thin coat of mixture is applied on the surface (paper or fabric) and an object or a negative of a photograph is exposed for minimum 20 minutes in the sun after which it is rinsed in cold running water. Further it is dipped in hydrogen peroxide solution for 5 minutes before leaving it to dry.
Prints obtained by exposing objects.
Prints obtained by exposing negatives of photographs.