ABOUT CYANOTYPES
Cyanotypes were discovered in 1842 by a chemist named Sir John Herschel, who found that mixing two chemicals together resulted in a solution that turned blue when exposed to sunlight. The cyanotype formula is made by mixing Solution A (25% Ferric Ammonium Citrate in water) and Solution B (10% Potassium Ferricyanide in water) together in a 1:1 ratio.
When a plant or other opaque object is placed on the surface of coated paper, it blocks sunlight during exposure, which prevents the covered solution from turning blue. To set or fix a cyanotype print, it is rinsed in running water, washing away any unexposed chemistry and stopping the exposure. The resulting print is a stunning Prussian blue and white negative of the item used during printing.
Herschel introduced the discovery of cyanotype to his friend, Anna Atkins, a botanist. Atkins had an impressive collection of plant specimens (which she later donated to the British Museum). Atkins quickly got to work using the cyanotype process to document the algae, ferns, and other plants in her collection. The process was faster and more accurate than drawing. In 1843, Atkins published her (and the worlds!) first book of photographs, called "British Algae" which was a hand-printed and bound book of cyanotype prints, each labeled in text that Atkins made from seaweed.
You may have seen cyanotype prints without even realizing - blueprints earn their name from the way they are made - contact prints on a surface coated with cyanotype solution! Blueprints are (unfortunately) no longer made using the cyanotype process. But, many people use digital negatives printed on transparency sheets or even hand drawn sketches on acetate to create prints that emulate a similar feel to the original blueprints.
