Red Iron Oxide

Red iron oxide, hematite, Fe2O3, produces a wide range of earthy glaze colours – yellow, brown, rust and near-black in oxidation firings, and blue/green celadons to black in reduction firings. Actual effects depend on oxide concentration, purity, particle size, degree of solution, glaze chemistry, temperature and firing atmosphere. Variability is due, in part, to the different oxidation states that develop during firing. 

For more information on red iron oxide, see the Digitalfire.com Reference Library of ceramic materials.