ABSTRACTTwenty‐five synthetic fluxes composed of ceramic materials, compounded in their eutectic proportions and fused to clear glasses, were added to a body of the semivitreous type in varying amounts, and their effect on vitrification was studied. It has been found possible to reduce the feldspar content of such a body to 8% and, by an addition of 2% of auxiliary glass, to develop almost any desired degree of body vitrification between 0.5 and 7.0% at a temperature as low as cone