A – ferric ammonium citrate, a green-yellow powder
B – potassium ferricyanide, a red-orange powder
+ distilled water
-> Both powders must be handled with the usual precautions as in a chemical laboratory, in particular, isolate the work area, prohibit any food or drink, do not ingest the products or inhale them. At the end of the work, thoroughly wash the surfaces that have been in contact (including the body!). These two components and the cyanotype emulsion that will be produced can be put into the waste water circuit.
Ferric ammonium citrate is a food additive better known as E381 and potassium ferricyanide is a harmless version of cyanide, once used to paint tomatoes red. It is now forbidden to use it in the building industry because this paint reacts with bleach, and there yes, it has a harmful effect. On the other hand “ferri” is still used in photography and offset printing.
-> For safety: do not approach bleach, soda or any other ammonia derivative, even to wash surfaces and utensils before or after.
-> I buy these ingredients at Disactis, on the internet.
-> It is possible to use tap water but the result will be less well controlled: distilled water ensures that there is no chemical variation due to the presence of minerals.