Annealing failure

[Franzeska]

The wind-up: I tried to change the RTC100 program on the fly but (of course) somehow confused the controller. After restarting the program and skipping the completed ramp phases to get back to the fast drop to 950, I got an error message (E A) and the controller refused to work. I made a couple of stabs at getting it to work again with the same result. Since it was around 3:30 a.m., I gave up and the kiln proceeded to cool naturally from 1025 deg, so of course there was no soak at 950. At 6:30 a.m. the temperature was around 560. My kiln cools veeeerrrryyy slowly when it gets to around 600 (2-3 degrees per minute, and even slower the cooler it gets). This was the second full fuse for this piece because I was attempting to cure a case of chicken pox (bubbles).

The pitch: What special care should I take when reheating this piece so that I can anneal it properly? Please recommend a firing schedule if special care is needed to anneal it properly. The schedule I was using was slow because it had already been fused:
100 300 10
150 1100 15
150 1250 60
400 1480 10
9999 950 60
150 800 10
300 100 0

Should I ramp up at 100? 150? Stop for a soak at 300? 1100? All of the above? Anneal soak longer than usual (60 min)?

Thank you for your generous help.

Franzeska

[Bert Weiss]

Franzeska

You don't mention how thick your glass is, or what sort of kiln you are firing in. 6mm glass can anneal with a shutoff, in some situations.

If all you want to do is be sure of a good anneal. Heat slowly to anneal soak temp, soak, and anneal.

Remember that stress is cumulative. If you have compatibility stress and you add thermal stress, you will see a problem develop sooner than a situation with no compatibility stress. Just because 2 glasses are compatible, doesn't mean they are stress free.

[Franzeska]

The kiln is an Olympic 1814GFETLC (or whatever they call their glass fusing clamshell).

The glass is System 96. There are two 11.5 inch discs. One is transparent, the other is Blackberry Opal Art. It will eventually be slumped into the seder plate mold with the deep cups.

I'll just go slowly and see what happens.

Thank you.

[Bert Weiss]

The kiln is an Olympic 1814GFETLC (or whatever they call their glass fusing clamshell).

The glass is System 96. There are two 11.5 inch discs. One is transparent, the other is Blackberry Opal Art. It will eventually be slumped into the seder plate mold with the deep cups.

I'll just go slowly and see what happens.

Thank you.

Diameter is pretty much irrelevant to annealing schedules. What counts is thickness, and whether or not the thickness is uniform or varies. I use the same annealing schedule for a 4" square as I would a 40" square, as long as the glasses are the same thickness. (By the time you get down to pendant size, you can go faster)