2 o 3 and or by increasing the proportion of the alkali metal oxides the fusion point can be reduced by increasing the proportion of b 2 o 3 cao and or the alkali metal oxides as between the two alkali metal oxides an increase in the na 2 o k 2 o ratio lowers the fusion point it is well within the skill of the ceramics art to apply these principles to make fine adjustments to the thermal expansion coefficients and fusion temperatures other materials can be employed in the glazes of the invention for instance mgo and or bao can be used in place of some of the cao some li 2 o can be used in place of some of the na 2 o and or k 2 o especially if fusion point reduction is desired small amounts of zirconia and zinc oxide can be added to th glaze and conventional pigments can be added in small amounts usually less than one weight per cent to tint the glaze such pigments include transition metal compounds such as vanadates manganates and chromates glazes were made having the compositions set forth below in table ii from silica tabular grade alumina potassium carbonate sodium carbonate calcium carbonate and boric acid the raw materials were blended ball milled for two hours and then transferred to a dense.