thermal shock issues
Posted: Wed Apr 21, 2021 7:05 pm
I've been using the same firing schedules for similar projects all year, but lately things are cracking in. half.
I had a 12 inch 6mm piece I was slumping. I made same thing last week and it slumped fine. lastnight I did another one but when opened kiln this morning it was brokej in half.
my firing schedule is basically 5 hours to get to 520 degrees c. then rest then slowly ramp until 680.
. not near my computer to write the exact schedule.
but I'm. wondering why same project cracked today but didn't last week.
could the kiln need recalibrate.
also I noticed during cool downs it reduces temperature from 800 degrees to 300 degrees in about 4 hours but takes 10 more hours to get to 50 degrees. is there a reason it's not cooling more consistent.
it used to hold temperatures more evenly. I didn't need to anneal before because it stayed at 500 degrees range for 2 hours on its own. but now if I don't anneal around 510- 520 it cracks also.
I'm. not sure if there is an insulation issue, a heating calibration issue, if it's the heating element, therkal couple, the programmer. just seems strange that the same schedules I've used for 2 years don't work anymore
I had a 12 inch 6mm piece I was slumping. I made same thing last week and it slumped fine. lastnight I did another one but when opened kiln this morning it was brokej in half.
my firing schedule is basically 5 hours to get to 520 degrees c. then rest then slowly ramp until 680.
. not near my computer to write the exact schedule.
but I'm. wondering why same project cracked today but didn't last week.
could the kiln need recalibrate.
also I noticed during cool downs it reduces temperature from 800 degrees to 300 degrees in about 4 hours but takes 10 more hours to get to 50 degrees. is there a reason it's not cooling more consistent.
it used to hold temperatures more evenly. I didn't need to anneal before because it stayed at 500 degrees range for 2 hours on its own. but now if I don't anneal around 510- 520 it cracks also.
I'm. not sure if there is an insulation issue, a heating calibration issue, if it's the heating element, therkal couple, the programmer. just seems strange that the same schedules I've used for 2 years don't work anymore