I hate it when things go wrong. It sucks.
But it's also a learning experience (I have to reluctantly admit).
This is what came out of my kiln last week one day:
This was going to be a bowl. So I had painted onto a round piece of glass, but fired it without frit behind the paint. I have done this technique before with no issues. I fired 2 other pieces at the same time, both with frit over them. One of them had some cracking in the paint like this, but after another firing, it was very barely noticeable and still an acceptable finished piece.
But there was no coming back from this. I am going to have to remake it. So, the only thing I can think of that caused this is a reaction between the paint and the metals in my water. The majority of the cracking was where I used or mixed in some yellow paint. The yellow can be tricky anyway, but there must be something in it that was very unhappy with my water. I usually fill my paint water bottle from my kitchen sink or refrigerator. Both of these sources are filtered water. We have an older home with metals in the water, including lead.
The last time I filled the bottle, I used the bathroom sink. I am hoping that is what the problem is - I am sure I will find out if my theory is correct. The paint manufacturer recommends using distilled water. I may get a bottle if I end up with anything similar to this disaster again.
Wish me luck!