Cracked from impurities?

[Mark Wright]

Wondering why the plate cracked? I fused an 8” x 8” plate 2 layers thick and it was great except a small piece of kiln brick was imbedded in the piece. I ground the kiln brick piece out with a diamond bit and put the plate back in the kiln with another piece. It cracked into two pieces with sharp edges, so it happened on the way down. The other piece is fine and I was worried about it because it had been fired multiple times. Maybe I did not get all of the fire brick removed?
I might mention this was a “make another one” of something I had done before with the same colors.

[Judd]

You're sure the glass was fusable glass? If you bought glass from Hobby Lobby thinking it was compatible - it ain't, and there's your problem.

If it was fusable, then perhaps you are cooling too quickly? You didn't post your schedule.

[Brad Walker]

Wondering why the plate cracked?Maybe I did not get all of the fire brick removed?.

This is my guess. I've seen cracks before that arise from impurities in the glass.