Cyanotype - is a photographic printing process that produces a cyan-blue print. Engineers used the process well into the 20th century as a simple and low-cost process to produce copies of drawings, referred to as blueprints. The process uses two chemicals: ammonium iron(III) citrate and potassium ferricyanide. http://www.tino.ca/index.php?/photography/blue/
Gum Bichromate - photographic printing process based on the light sensitivity of dichromates. It is capable of rendering painterly images from photographic negatives.