A photographic process which uses iron salts (Prussian blue) to produce monochromatic bluish prints with white lines.
Cyanotype technology was developed by British photography pioneer Sir John Herschel (1792-1871) in the early 1840s and is notable for not requiring silver halides. Instead, iron salts - typically a mixture of ferric ammonium citrate and potassium ferricyanide - are used. Cyanotypes were commonly used for printing blueprints in the days before photocopiers and laser printers (xerography).
In fact, the first known published book to be illustrated photographically contained photograms created using the cyanotype process. The book, British Algae: Cyanotype Impressions Part I, was written by British botanist Anna Atkins (1799-1871) and was published in 1843.
cf. photogram, silver halides.
Entry last updated 2002-04-25. Term 304 of 1487.
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