Sun Print Paper

This light-sensitive paper changes colour from white to a very vibrant blue when exposed to UV light, and can be used to create photographic reproductions of objects or documents, known as cyanotypes or ‘blueprints’. 

Whereas black and white and modern colour photography both use light-sensitive silver compounds in the production of photographic negatives, cyanotyping relies on the light sensitivity of iron salts, typically a solution of potassium ferricyanide and ferric ammonium citrate, to create a ‘contact print’ in a process similar to photocopying. These ‘sun-print’ sheets are brushed with an iron salt solution, and dried in the dark. The object you want to reproduce is placed on top of a sheet, and it’s placed in direct sunlight for about two minutes, until the parts of the paper exposed to sunlight turn blue. The object - which can be anything from a plant specimen to a drawing or negative - will stop the light from reaching selected parts of the paper, and a white impression of the subject will be formed on the blue background. The paper is then washed in water, which oxidises the iron salts producing the brilliant blue, or cyan, print that gave the process its name.

The images below show homemade sun print paper being used to make cyanotypes with light artist Angela Easterling at our Light Public Open Day in 2015.