It happens to all of us sometimes, but man, it can be so frustrating - - wasted torch time.
This happened to me last night. I was going to work on more turtle beads (which I must post later, they're so darn cute!) for Beads of Courage, but I decided to make another complex flower murrini instead (big mistake!).
Everything was going fine until my last petal layer when I heard the distinct sound of glass cracking. You other glass artists out there know what I mean - - that high-pitched, make-you-cringe, tinking sound. Ugh! Yep, my huge (about 3" round) murrini cracked in an underlayer.
I proceeded to heat the begeezus out of it and was hoping it would heal. If anyone out there has made murrini before, they know the whole mass of glass needs to be heated to pull out into a usable rod size anyway, so it was heated thru-and-thru for that part also.
I pulled it into a 4-foot long rod of about 8-10mm thick, and everything seemed fine, until it cooled. Then the cracking began - - little tinks here and there. I was working on a turtle bead then, looked over, and half my murrini rod split in 2, lengthwise. Oh boy.
I decided to test the remaining, un-cracked rod, and proceeded to make one test murrini bead which seemed fine. I went to test a second bead and the rod just kept exploding in my flame, pieces of pretty pink and yellow flower murrini glass all over my workbench.
So much for 3 or so hours at a hot torch, what a waste of time, glass and electricity. But, it happens sometimes, to all of us.
Here's a picture of the little glass chunks all around my torch and 3 pieces of split-in half murrini - ugh!