A couple small mugs (from a set of about 50) I tested glazes on. The kiln got way too hot, casing the glazes to turn out bad, drip, and the clay to shrink far too much. I hope the other mugs turn out better.
yes its a good idea to be cautious of any glaze. Generally it's the super bright ones though that can be the most problematic as they tend to have the heavy metals. I'm not too knowledgeable about glazes though, so I just check the recipe first to make sure.
anything w/ Barium is NOT functional. usually if it has less than 10% barium carbonate you can substitute Strontium carbonate. I have done this and there is not much of a color difference. and this comes directly from my instructor Louis Katz @ TAMUCC.