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.
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