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I built three panels approximately 19 inches by 24 inches and approximately .25" to 3/8ths inch thick. The firing schedule I used is:
150 500 20
150 800 20
150 1100 20
50 1250 10
9999 1470 20
9999 960 4 hours
100 700 1 hour
I cold worked the panels. the client installed the panels into a window in MN.... As you'll be able to see in the pictures I have cracks in two out of three of the panels... I thought my anneal was long enough... are there other things to consider - hot - cold - stress from installing this way? Do you think the anneal is the culprit? Thank you so much for your thoughts!

Brad, not sure how to "Just ask Brad" but, I'd be very interested on your thoughts.

Hi kdd,

Beautiful panels. Your schedule is very conservative and should be fine. At most, you may want to drop your anneal drop temp. to 80 or 90f/hr. I would examine the mounting frame with a steel straight edge to look for a high spot near the middle. If there is, and the glass is pressed tight on the sides, it is inviting a stress fracture most likely to show up with a variation in temperature. I couldn't see the fracture in the top piece, but the bottom one looks like what one could expect in the circumstance described. Good luck.

Warren

Thank you Warren