
The technique was invented in 1841 by astronomer and scientist Sir JohnHerschel, and was popularised by photographer and botanist Anna Atkins. Her book ‘Photographs of British Algae: Cyanotype Impressions’, published in October 1843, is considered the first photographically illustrated book.
Mainstream photography eventually adopted cyanotype as a copying technique and this became known as a “blueprint”. This blue, called Prussian Blue, was used in reproductions of large architectural and mechanical drawings.

Variations of the original formula involve different ratios of the following chemicals:(1) Potassium ferricyanide and (2) Ferric ammonium citrate(green). Too much potassium ferricyanide in the solution will lower printing speed; too little may cause the blue color to bleed into the lighter areas. Basically equal volumes of the two solutions are used.

Caring for your cyanotype: HERE