This green-colored salt is one of the two components needed to prepare the liquid cyanotype mix.
The liquid resulting from the dissolution of Ferric Ammonium Citrate is usually known as Solution A. The name of solution B commonly corresponds to that made by Potash Ferricyanide.
Ferric Ammonal Citrate is a chemical that is very susceptible to environmental humidity, it should be protected from humidity. It has a limited conservation (being able to lose properties) and once opened its state must be checked before using as it has a tendency to cake and harden. Both chemicals for cyanotype preparation can be purchased separately or together in a kit.
There are many recipes and formulas to achieve a strong and stable cyanotype solution. The best thing is to do tests and draw conclusions, but here we leave you one that has worked for us:
25 grams of Ferric Ammoniacal Citrate diluted in 100 cc of distilled water
15 grams of Potash Ferricyanide diluted in 100 cc of distilled water
As for the papers, a whole world of possibilities opens up. We recommend choosing papers that have at least 200 gr. and that allow to be bathed under water. Papers for intaglio engraving or lithography are usually a very good option. If they are too absorbent, the cyanotype liquid will be absorbed by the fiber of the paper, generating images that are fainter than desired. To avoid excess absorption of the paper, we must look for papers that have a minimum of glue or correct the pore using, for example, rabbit glue.
A brief addition of hydrogen peroxide in the water during the wash will increase the intensity of the cyano blue characteristic of this technique.