Somehow my earlier comment ended up in a discussion about band saws, hope I get it right this time.

What is the cause of surface pitting?  Some of my 1x1 tiles get it, other times not.  Seems like there are so many variables! Frit size, kiln temps?

I thought I was getting dialed in on a tile making project I have been doing but intermittently my 1 x1 tiles have some surface pitting.  What causes surface pitting?  Even tiles with no apparent bubbles sometimes get it.   I am using a fairly fine frit.   Is it true that the finer the frit  the worse the bubbles?