Blistering in a high gloss cone 6 glaze fired at cone 7R

Thursday 20th October 2016

The boron and zinc fluxes make the melt of this glaze highly fluid at cone 7R. That comes with consequences. Notice the Al2O3 and SiO2 in the calculated chemistry. They are at cone 04 levels. The significant ZnO increases surface tension of the melt, this helps bubbles form at the surface (like soap in water). Al2O3 and SiO2 could be added (via more clay), this would stiffen the melt so the large bubbles would be less likely to form (this glaze melts so well that it could accept significantly more clay without loss in gloss). A drop-and-soak firing is another option, in this case a drop of more than 100C might be needed (see the link below to learn more).

Pages that reference this post in the Digitalfire Reference Database:

Blistering in a cone 6 white variegated glaze. Why?, Melt Fluidity, Fluid Melt Glazes, Cone 6 Drop-and-Soak Firing Schedule

This post is one of thousands found in the Digitalfire Reference Database. Most are part of a timeline maintained by Tony Hansen. You can search that timeline on the home page of