Exposed but not developed Cyanotype Print

A sheet of exposed cyanotype chemical paper with the fern that blocked the UV light. Exposure to UV light has caused the chemicals to turn blue. The next step would be to wash the print in water. In this process an object is placed on the ultraviolet sensitive chemically treated paper and exposed to a strong UV light source – in this case sunlight. The object is then removed and the print washed in cool water to remove the unreacted chemicals. Cyanotype is a photographic printing process that produces a cyan-blue print. Engineers used the process well into the 20th century as a simple and low-cost process to produce copies of drawings, referred to as blueprints. The process uses two chemicals: ammonium iron(III) citrate and potassium ferricyanide. The English scientist and astronomer Sir John Herschel discovered the procedure in 1842.

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Filename: K14-cyanotype-7.jpg
Copyright: Ted Kinsman / Science Source Inc.
Image Size: 5008x3744 / 10.3MB; calotype cyanotype first science photo use history of photography history of science photograph photographic photography scientific photography ultraviolet UV sensitive UV sensitive indicator uv indicator ferricyanide Sir John Herschel Herschel John Herschel fern sequence
Contained in galleries: science

A sheet of exposed cyanotype chemical paper with the fern that blocked the UV light. Exposure to UV light has caused the chemicals to turn blue. The next step would be to wash the print in water. In this process an object is placed on the ultraviolet sensitive chemically treated paper and exposed to a strong UV light source – in this case sunlight. The object is then removed and the print washed in cool water to remove the unreacted chemicals. Cyanotype is a photographic printing process that produces a cyan-blue print. Engineers used the process well into the 20th century as a simple and low-cost process to produce copies of drawings, referred to as blueprints. The process uses two chemicals: ammonium iron(III) citrate and potassium ferricyanide. The English scientist and astronomer Sir John Herschel discovered the procedure in 1842.