Same glaze, same kiln, same clay: The right one crystallized. Why?

Tuesday 11th July 2017

Well, actually they are not exactly the same. This is 80% Alberta Slip and 20% frit. But the frit on the left is Ferro 3195 and on the right is 3134. By comparing the calculated chemistry for these two we can say that the likely reason for the difference is the Al2O3 content. Frit 3134 has almost none whereas 3195 has 12%. Al2O3 stiffens the glaze melt, that impedes crystal growth. But it stabilizes the melt against running during firing. Frit 3195 has more boron, so the one on the left should be running more. But it actually runs less. Why? Again, because the increased Al2O3 is stiffening the melt.

Pages that reference this post in the Digitalfire Reference Database:

Ferro Frit 3195, Ferro Frit 3134, Al2O3, GA6-A - Alberta Slip Cone 6 Amber Base Glaze, Crystallization

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