A Classical Photographic Process | Cyanotype
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The cyanotype process was invented by the astronomer and chemist John Frederick William Herschel.
The name cyanotype was derived from the Greek name cyan, meaning “dark-blue impression.”
The inorganic pigment Prussian blue (hydrated iron hexacyano ferrate complex), which is the image-forming material of cyanotypes, was prepared first by Heinrich Diesbach in Berlin between 1704 and 1710.
The cyanotype process was seldom used until the 1880s, when it became a cheap proofing process for collodion, dry gelatin plates, and gelatin roll film before the final printing, which used more expensive silver- or platinum-based photographic processes. From the 1870s until about the 1950s, when it was replaced by diazo- based reprographic processes, the cyanotype process and its variants were the primary processes used by engineers and architects to copy plans.
The cyanotype process, together with a number of other, older photographic processes, was revived by contemporary photographers in the 1960s. The older processes were considered alternatives to the silver gelatin process using commercial photographic material.
It is interesting to note that today, as digital photography replaces all applications of classic “chemical” photography, the silver gelatin process itself will soon be considered an alternative photographic process.
The cyanotype process was one of the first non-silver technologies used to
create photographic images. Originated in the 1840's, it was not utilized in mainstream photography and was adopted as a copying technique, becoming known by the term "blueprint", with its blue background reproductions of large architectural and mechanical drawings.
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To begin the process, two solutions are prepared for the two-part sensitizing process. Material sensitized with the solution is then printed by ultraviolet light. The process was introduced in the 19th century. Unlike the silver process used in traditional black and white photography, cyanotype photographs are made using a solution of iron compounds that react to UV light. Images can be taken with a camera or made by placing objects directly on the paper.
The relative simplicity of the cyanotype printing makes it a great introduction to those new to alternative process printing, while the beautiful tonality and artistic flexibility also recommends it for serious fine art practitioners.
The cyanotype process is relatively non-toxic (although rather messy so wearing old clothing is recommended), and printing techniques can be carried out in normal ambient light, which makes this printing technique ideal for a home workshop or studio.
Unlike photographs set in silver, like in black and white photography, cyanotypes are using a solution of iron compounds.
The paper is coated with 2 chemicals called potassium ferricyanide and ferric ammonium citrate. Once exposed to a source of ultraviolet light, such as sunlight, a chemical reaction occurs forming ferric ferrocyanide, a blue dye known as Prussian blue. When objects are placed on treated surfaces, they block the sunlight from reaching the paper in those areas, so they remain white. Exposed areas will turn blue.
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The photograph can be taken with a camera, like a digital camera, and the resulting photo turned into a negative that can be used to make a cyanotype. The basic cyanotype recipe has not changed very much since Sir John Herschel introduced it in 1842. The cyanotype process is over 160 years old.
It was used for the first photographically illustrated book, and later became popular with some pictorialists, for whom a commercial paper, called ferro-prussiate, was marketed.
Being simple, cheap and fairly permanent, it also enjoyed an extended period of commercial success as the blueprint process for copying drawing-office plans, until it was made obsolete by the invention of dry, plain paper photocopying. The word 'blueprint' still persists in our language, however, with an expanded meaning.
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