English Scientist Sir John Herschel experimented and invented the cyanotype process, the first photographic process that did not use silver. The two chemicals used in cyanotypes are ferric ammonium citrate and potassium ferricyanide. Most historical accounts of cyanotypes give the origin as the early 1840s, but Herschel was experimenting with his process, many years earlier, probably in the 1830s when Daguerre and Fox-Talbot were experimenting with their photographic processes.
The cyan-blue prints produced by Herschel, were vivid and interesting, he found that by varying the chemicals and reagents as diverse as wine, tea and cat urine , he could produce other colors too. His first choice however was cyan-blue. Other colors exist in photographs and are quite rare; red, yellow, orange and green.
Although the process did not find popular use for decades, the subtleties of the cyanotype are delightful. Toward the end of the nineteenth century, the process was widely used to produce blueprints for large architectural and mechanical drawings.