2023-02-01
Cyanotype is a photographic printing technique that uses light. Key to the cyanotype is the use of light sensitivity of iron salts. With this technique, the result is a blue monochrome image.
The cyanotype method was invented in 1842 by an English scientist, Sir John Herschel, who used it to copy notes and engravings. However, this technique did not gain popularity until 30 years later, thanks to which cyanotype began to be used to copy documents and to make copies of plans (blueprint). Cyanotype was also used to create photograms – images that were made without a camera, using only sensitized paper on which were placed, for example, plants.
Professional photographers also used blue prints, but because of the lower cost and simplicity of making them, it was initially treated as an inferior technique. It was rediscovered in the 1960s as an alternative to the gelatin-silver technique. "Prussian blue" tonalisation was also learnt, resulting in new colors for prints and a more permanent image.
To make a cyanotype, the unexposed portion of the iron compound must be washed out. In this traditional photographic technique, iron is used instead of silver salts, which has light-sensitive properties. Potassium ferricyanide and water are applied to paper or other material in a darkroom to form a photosensitive layer, which is then allowed to dry. Then the paper is exposed by direct contact with the negative and sunlight.