Main Page | See live article | Alphabetical index Cyanotype is an old photographic procedure which typically admits a cyan-blue colour. The English scientist and astronomer Sir John Herschel discovered this procedure in 1842. It uses two chemicals: Ammonium iron (III) Potassium ferric cyanide They result in an photo-sensitive solution when solved in water, which is used to coat a material (usually paper), then a positive image can be produced in by exposing it to a source of Ultraviolet light (such as sunlight) with a negative. The developing of the picture takes place by flushing it with flowing water. The water-soluble Iron (II) salts are washed away, while the non-water-soluble Iron (III) salt crystalls remain in the paper. These give the picture its typical blue color. See also: Photographic processes This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.