The recipe contains 6% red iron oxide. The chemistry is high alumina (from 45 feldspar and 20 kaolin), zero silica silica (4:1 Al2O3:SiO2 ratio) and 20% calcium carbonate. The remainder is a little talc and calcium phosphate. The reduced iron is fluxing what would otherwise be a very matte surface. Reducing the iron percentage to 4% produces a yellow mustard color.
|Materials||Iron Oxide Red|
|Oxides||Fe2O3 - Iron Oxide, Ferric Oxide|
|Oxides||FeO - Ferrous Oxide|