Glaze crystals cobalt blue expect the unexpected with these glaze crystals add to glazes prior to decorating bisqueware or sprinkle onto wet glazed surfaces for a more controlled area selection the final outcome of these crystals depends on the temperature of the firing the higher the firing temperature the more dispersed they become so the results can range from just dots to having the appearance of oil on water use sparingly for better effects lead free and non toxic firing range 1044