What are the chemicals in solargraphic paper?

[amuderick]

They sell paper with a blue coating in kids stores. It comes in a black bag. You put it in the sun with various things on top of it and where the sun hits (UV-light), it turns white. When you wash the paper in water, the reaction becomes fixed. What is the formula?

 

[Photo Engineer]

Sounds like cyanotype. Formulas for that are all over the photo sites. The Formulary sells kits.

PE

 

[psvensson]

Yup, the solargraphic kits seem to be the very simplest form of cyanotype: potassium ferricyanide plus ferric ammonium citrate. They're nearly harmless and easily mixed from scratch.