The blueprint [[process]] is essentially the cyanotype process developed by the British [[astronomer]] [http://en.wikipedia.org/wiki/John_Herschel John Herschel] in 1842.[1] The photosensitive compound, a solution of ferric ammonium citrate and [http://en.wikipedia.org/wiki/Potassium_ferricyanide potassium ferricyanide], is coated onto paper. Areas of the compound exposed to strong [[light]] are converted to insoluble blue ferric ferrocyanide, or [http://en.wikipedia.org/wiki/Prussian_blue Prussian blue]. The soluble [[chemicals]] are washed off with water leaving a light-stable [[print]]. | The blueprint [[process]] is essentially the cyanotype process developed by the British [[astronomer]] [http://en.wikipedia.org/wiki/John_Herschel John Herschel] in 1842.[1] The photosensitive compound, a solution of ferric ammonium citrate and [http://en.wikipedia.org/wiki/Potassium_ferricyanide potassium ferricyanide], is coated onto paper. Areas of the compound exposed to strong [[light]] are converted to insoluble blue ferric ferrocyanide, or [http://en.wikipedia.org/wiki/Prussian_blue Prussian blue]. The soluble [[chemicals]] are washed off with water leaving a light-stable [[print]]. |