The cyanotype or sun print is an alternative photographic printing process that produces a rich Prussian blue print using a photo sensitive solution of iron salts rather than silver salts. These prints are made on 100% rag watercolor paper or Kozo paper hand coated with cyanotype solution (Potassium Ferrocyanide and Ferric Ammonium Citrate) and allowed to dry in a dark room. The cyanotype is then exposed to the sun or an ultraviolet light using lace, stencils, negatives, objects or drawings on a transparent surface. After exposure, the unexposed solution is washed off the paper and the image if “fixed” with water. Each print is unique.

British chemist & astronomer Sir John Herschel invented the cyanotype process in 1842 as a means to copy letters. It was later used to make camera-less photograms, notably of botanical specimens, by Anna Atkins.

Because it is one of the easiest and simplest photographic printing processes to use, it was often used by early photographers to make proof prints. It also found widespread use in architecture and engineering firms as a way of copying drawings and plans, called “blueprints”.

I am frequently surprised how this chemical process transforms tattered and yellowed textiles into worldly photographic images.