WarmGlass.com

Thanks. I'm on a mission to solve and will report back.

Interesting, never thought about the shelf or wash. I have two shelves but I haven't correlated whether it happens on a particular one. I have switched my brand of wash, that might be a factor. I'll try experimenting, just hate wasting the materials.

I have over 900 firings in this kiln and lately the large pieces have developed a large bubble while doing a full fuse -- a schedule that has worked well for years. Could it be the coils, heat, what???? I'm anxious for suggestions. I can return it to the manufacturer for an overhaul if push comes to...