Week 1 - Cyanotypes

Week 1 - Cyanotypes

History
Cyanotype is a printing process that produces a blue print. Engineers used this as a simple and low-cost way to produce copies of drawings, named blueprints. The chemicals used are ammonium iron(III) citrate and potassium ferricyanide.

Process

Equal amounts of an 8.1% (w/v) solution of potassium ferricyanide and a 20% solution of ferric ammonium citrate are mixed and painted on to paper and dried in a dark place. We pulled the curtains down in the class and placed our paper with the solution under a dark spot under the desks to dry. Once dried we gathered up the paper and placed objects on top of the dried solution and set it down in direct sunlight for 7 minutes. After 7 minutes the dried solution turned a slate grey colour on the paper.

We removed the objects from the paper and submerged the paper in a shallow tub of water and washed away the yellow unreacted solution. Once done the paper became blue and white.