glass breaking

[AJK25]

i have been fusing small pieces of glass for many years now (1.25" square, between 3 and 5 layers of 3mm Bullseye fusible glass). I've had no problems until recently. Some of my glass has started to break off, and i'm not sure why. Somebody told me that it may be because of the thickness of my kiln shelf, but i am using the same shelfs that i've always used (5/8" thick). I am thinking that maybe my firing schedule is the culprit...although it seems strange that i've never really had a problem in the past.

My firing schedule is:
500 degrees/hr to 1400 and hold
AFAP to 960 and hold for 1.5 hours
180 degrees/hr to 750 and turn off

Am i going too fast in my last firing phase? Someone suggested I slow it down to 45 degrees/hr to 700.

Drew

[Warren Weiss]

Drew,
I would go 350 d/hr to 1000, then 500 to 1400 (or 1450 if you want a full fuse.)
afap to 900 (Bullseye recommended annealing temp.)
Hold for 1.75 hrs (especially for 5 layers.)
Go 100 d/hr to 750, then off
Warren

[rosanna gusler]

check to see if your thermocouple has degraded. your temps could be off. r.

[AJK25]

thanks for your suggestions, Warren and Rosanna. I appreciate it.