Vince’s Decorating Slip with recipe for Black
Just to build on Mason Stain Best Black #6600
Chemical Name: Iron Cobalt Chromite Black - Spinel
Chemical Formula: (Co,Fe)(Fe,Cr)2O4 but also includes some Nickel as a modifier.
Spinel is a composite mineral classed as Magnesium Aluminate and has the formula MgAl2O4, when made artificially it requires temperatures of around 1800C to melt all components in the mix including metallic oxides responsible for making it black, so because the colourants are bound by the high amounts of alumina and magnesia they are not able to be released into the glaze matrix and not allowing cobalt to be liberated thus not staining the glaze blue.