Cyanotype

About

Cyanotype is one of the oldest monochrome processes that do not use silver salts.

19 rue Blanche (9e arr.) ; architecte F. Delmas, album photographique Les Constructions nouvelles (50 photographies), Société des Ingénieurs civils de France, cyanotype monté sur carton dans un album, 27,5 x 22 cm (épr.) ; 41 x 31 cm (sup.)

Historical period of production and use

Invented in 1842 by English scientist John Frederick Herschel, the process was a late success: its deep, intense blue and pictorial results did not appeal to photographers of the time, who were seeking a more realistic rendering. It was used at first essentially for documentary purposes, such as copy making, architectural plans, and industrial drawings. In the 1840s-50s, however, it did draw the attention of two main photographers: the English botanist Anna Atkins, who used it to produce photograms of dried plants, and the French artist Henri Le Secq, for his work on the gothic monuments of Paris and his still lifes. The process finally became popular in the late 19^th century. It was valued by the pictorialists, particularly Paul Burty Haviland, who were keenly interested in its aesthetic qualities. Today, cyanotype is used by many contemporary artists, such as Nancy Wilson Pajic, who has contributed to its revival.

Manufacturing

Based on the reaction of iron salts to light, it is a relatively quick, simple, and low-cost implementation. A solution of ammonium iron citrate and potassium ferricyanide is applied onto the paper, which is then allowed to dry in a dark place. The print is then made by contact with the negative matrix. Exposure to natural light can last up to fifteen minutes, depending on the brightness, resulting in a change in the composition of the iron salts. The paper is then rinsed with water to dissolve the unexposed iron salts, and dried. The characteristic Prussian blue pigment is formed during this drying process.

Identification

The Prussian blue colour is the main clue for identifying a cyanotype. However, cyanotypes may be toned and take a warm brown hue similar to that of salted paper. They can then become difficult to identify.

Deterioration

Cyanotype is a chemically stable process. The cellulose in the paper support can often degrade faster than the photograph itself.

Credits

Visual Glossary of Photographic Processes © ARCP / Mairie de Paris, 2023

Glossary