The process was developed in 1842 by the English astronomer and natural scientist Sir John Herschel.
Unlike classic, analogue black and white photography, this process is not based on silver but on iron, which also produces the typical blue hue.
Historically, it was the third process to succeed in permanently fixing a photograph.
The natural scientist Anna Atkins is considered the first female photographer due to her early use of this process, in which paper is soaked in a chemical solution and made light-sensitive.  
She used the printing technique to document plants in detail.


Paper or fabric treated with a solution of potassium ferricyanide(III) and ammonium iron(III) citrate reacts photosensitively to sunlight and forms the dye Berlin blue (also Prussian blue, Parisian blue).