Photos will help--the nature of the break will often narrow down the possible causes.
Here's the before photo:
Could you list the style numbers of glass that you used? Was it all Bullseye?
It was all BE double-rolled glass. The flow slab was made from black and white 3 mm opalescent, sliced 6 mm thick. The border (seen in the photos) was 6 mm black. (Neither of the black pieces were stiff black. The top layer was 3 mm double-rolled crystal clear. I'll look up the style codes, but I think this description should be definitive.
What kind of kiln do you have? Describe the locations of the elements (top, sides, door, floor)
What size is your kiln?
Paragon Fusion 14, a top-fired 14" square kiln.
What did you use for dams?
Sawn pieces of kiln shelf, about 1/2" x 1" x 12" each. I used a narrow strip of 1/16 BE shelf paper inside of each dam.
How far are the dams from the elements?
The tops of the dams were about 3 1/2" from the lid, and the elements are recessed about 3/8 into the grooves in the lid. The glass was about 4" below the lid.
Also, if for some reason your kiln is not heating evenly, a longer anneal soak will not anneal the glass. You might need to run a "Knowing Your Kiln" test to see if there is a cold or hot spot in your kiln. (I'm not saying that this is the cause in your case. It is just one of the variables to check.)
While we have not run exactly that test, the kiln has seemed to fuse everything evenly, including when we have fused a number of small, similar pieces in different areas of the shelf simultaneously. The kiln is about 6 months old, and the elements are in good shape. I don't think uneven heating is the culprit.
I hope the photos provide some clues. Thanks for your help.
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