Cyanotypes

A cyanotype is a contact print created using light sensitive iron compounds invented by Sir John Herschel in 1842. Herschel was not a photographer, but rather a scientist seeking a method for copying his notes.

To create a cyanotype, a sheet of paper is coated with solution and left to dry away from exposure to light. An object or drawing is then placed upon the paper and exposed to light, leaving a white image underneath the object where light did not penetrate. The areas exposed to light turn a deep Prussian blue, and the paper washed to remove the remaining light sensitive iron compounds. The process is based upon the reaction of light with iron salts.

First called shadowgraphs, the images were eventually called cyanotypes for the brilliant color of the exposed paper. The process was used extensively to copy architectural plans, leading to the term "blueprints." It was used until the invention of mechanical methods such as copiers and computer printers.

Quick Facts

• Anna Atkins, a 19th-century botanist, was the first person to illustrate a book using cyanotypes exclusively. In 1843, Atkins published a book of 424 images of ferns and other plants, preceding Henry Fox Talbot's documentation of the calotype
• While developing the cyanotype method, Sir John Herschel conducted more than a thousand photographic experiments with dozens of materials. The experiments included using plant extracts, gold, and urine before settling on the iron-based solution in practical use
• Although relatively rare, a number of contemporary artists continue to work with cyanotypes. Notable among them is the artist Christian Marclay, who creates cyanotypes from deconstructed cassette tapes