Cyanotypes

One of the earliest photographic processes is the cyanotype, invented in 1842 by Sir John Herschel. He discovered a process by which he could make color photographs on paper in great detail but only in the shade of blue. The invention was based on the reaction of certain iron salts to light, and he named it the cyanotype (after the Greek cyan, meaning "deep blue"). One of the advantages of the process was its simplicity: Only a few chemicals plus water and sunlight were needed to yield visions of startling beauty.