It is one of the oldest photographic printing processes, having been invented by Sir John Herschel in 1842. The essence of Herschel’s discovery was that paper impregnated with certain iron salts was light sensitive: a Prussian blue image being formed when exposed to light. Anna Atkins used it for botanical studies in 1850’s. Engineers and architects used this process for reproducing technical drawings and continued to use ‘blueprints’ until quite recently.
The cyanotype is a contact printing process i.e. the negative and image are the same size. Prints can be made on a variety of acid free watercolour papers, some rice papers and fabrics such as silk and cotton. Images can be further enhanced by toning, handcolouring or superimposing over or under other printing processes such as gum bichromate to give another dimension.
