Cyanotype

1842–present

Prussian blue photography — iron-based process producing vivid blue images. Anna Atkins used it for the first photo-illustrated book.

Paper coated with iron salts (ferric ammonium citrate + potassium ferricyanide). UV exposure creates Prussian blue.

1 artist6 colors

Cyanotype Process

British

Invented by Herschel in 1842. Anna Atkins' botanical cyanotypes are the first photographs used for scientific illustration.

Iron-based, not silver. Prussian blue (ferric ferrocyanide) is the image substance. Architectural blueprints use the same chemistry.