SupplyCobalt Oxide, Tricobalt Tetroxide(XCo2O3·YCo3O4). A consistent, reliable, and stable, black oxide powder which used to give a brilliant blue/black color glaze and enamel. It can be applied through brushwork, decals, or other surface decorating techniques in ceramic glazes and underglazes. It can be also added to porcelain or stoneware clay.