Though this is not an outstanding photograph, nevertheless you can see that something not good happened here. The sundae dish shattered, apparently during the firing (as opposed to "while cooling.") It was thrown of B-mix 10, glazed with Magic White, and what's worse, through my small opening, I can see two other pots with that combination, and both have either cracked or shattered.
My first thought is that glaze tension tore this piece apart. There is no applied glaze on the outside, but I thought the soda glass would exert sufficient tension to compensate. And perhaps it would have; this piece may have been ruined before I applied the soda. Magic White fluxes relatively early. I've used Magic White on B-mix before with no surprises, but I do remember thinking as I applied the glaze that it was mixed a little thick in the bucket. I could have added water, but I didn't think I really needed to. The sundae cups are thinner than most things that I make, because they are stretched vertically after throwing. Between these two variations -- glaze thickness and pot-wall thinness - I guess something had to give.
There are at least 10 more pieces similar to this one in the kiln. I suppose they will all have torn themselves apart in this manner. I can only hope they didn't take too much other stuff with them.