Iron chromate (FeCrO3) is a brownish powder that creates darker colors when added as a colorant to engobes, slips and underglazes. As a colorant, it typically produces grays, by itself. Iron chromate can produce additional colors when mixed with other chemicals, as well, as is detailed below:
Iron chromate + cobalt or magnesium = blacks
Iron chromate + tin = pinks, reds
Iron chromate + zinc = browns
Suggested concentrations of iron in slips and glazes are as follows:
0.5 - 8% in slips
up to 15% in glazes
Iron chromate is highly toxic if absorbed through the skin, inhaled or ingested. Please use protective coverings when working with this chemical.