A cyanotype is a photographic process founded in 1842 by Sir John Herschel mainly as a way of reproducing documents known as blueprints. About a year later, Anna Atkins famously used the cyanotype process to document physical algae specimens and became the first person to illustrate a book using photographic images.

Cyanotypes are created using a 1:1 ratio of ferric ammonium citrate and potassium ferricyanide. Once combined they become reactive to the sun.