Colemanite in glazes is notorious for causing problems, spitting/blowing off the pot surface. I understand that this is due to rapid decomposition of the material when heated (is that right?).
So, is there a case for calcining colemanite to reduce this problem? If so, at what temperature?
I'd be happy to use a calcium borate frit instead, but don't have easy access to such a beast in my little European corner.
Anyone tried it?