Making black using metal oxides normally involves cobalt oxide, manganese dioxide, copper oxide and iron oxide. Combined they typically comprise 10-15% of the recipe. Using the Alberta Slip GA6-B base recipe, only 4% Mason 6600 black stain is needed to get a jet black! These blacks were applied in varying thickness on a porcelain and buff stoneware before having the white second layer applied. The black glaze on the top-right tile only has 3% stain. The overglaze is a gloss white with increasing amounts of tin oxide added (4-7%). Beyond 5% there appears to be no advantage.
GA6-B - Alberta Slip Cone 6 Amber Base 2
An amber-colored glaze that produces a clean, micro-bubble-free transparent glass. Works well on brown and red burning stonewares.
A mottled glaze created by double-layering glazes of different melt fluidity and color
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