The cyanotype process was introduced by Sir John Herschel in 1842 and has not changed since then. As early as October 1843, Anna Atkins began issuing published folios of her photograms, “British Algae: Cyanotype Impressions”. Her botanist father, John Children, was a friend of Herschel and they lived just 30 miles apart in Kent. Both were members of the Royal Society when Herschel announced his discovery of the cyanotype in 1842. The first commercial use was in 1876 at the Philadelphia Centennial Exhibition for schematic blueprint drawings for builders and engineers.
There are two chemicals employed in a traditional cyanotype formula, mixed together in equal parts. These are a 25%w/v solution of Ferric ammonium citrate and a 10%w/v solution of Potassium ferricyanide. The paper is coated in subdued light and the negative placed in contact and exposed to UV light, usually the sun. A wash in water completes the process.
These images below are not true cyanotypes, they have been produced digitally to replicate a cyanotype effect.
“…only a vandal would print a landscape in cyanotype.” – Peter Henry Emmerson (1856-1936)