Improper Annealing-Can this piece be saved?

[Carrie Loosz]

After a piece I made was fully fused, I discovered that I had mistakenly entered the wrong information in the annealing segment. So, even though the piece hasn't cracked yet, I think it most likely will at some point. Is it possible to refire it so that it can be saved? It's now 1/4" thick, so if this can be done, what type of firing schedule would be appropriate for System96 glass? Any advice would be appreciated.

[Morganica]

What did you enter and what were you supposed to enter?

[Bert Weiss]

Given that your piece is only 1/4" thick, chances are the annealing from a simple shut-off will suffice. If you worry about it, you can give it a conservative reheat and reanneal. The only anneal that matters is the last one you did. Once the glass is heated above the strain point, all stresses are gone. You anneal to deal with the new stresses that get set up as the glass cools.

[Carrie Loosz]

Thank you so much, Bert. I am relieved that it can be refired, as I had spent a lot of time designing and preparing this piece as a special gift.

Morganica, I'm embarassed to say that I mistakenly entered 60 degrees F instead of 950 degrees F for the annealing segment. The full rapid decent from the processing temp. of 1460 degrees F caused the kiln to fail and shut off at some point, so the annealing segment, hold time, and cooling segments were completely lost. My kiln has thick fire brick and takes all night to cool to room temp., so there must have been just enough heat to keep this piece from shattering. Lesson learned ~ don't program a firing schedule when over-tired and suffering with a throbbing headache. I usually double check and sometimes triple check my programming, but this time I didn't. I welcome any tips you might add to Bert's for a successful re-firing.

[bob proulx]

Thank you so much, Bert. I am relieved that it can be refired, as I had spent a lot of time designing and preparing this piece as a special gift.

Morganica, I'm embarassed to say that I mistakenly entered 60 degrees F instead of 950 degrees F for the annealing segment. The full rapid decent from the processing temp. of 1460 degrees F caused the kiln to fail and shut off at some point, so the annealing segment, hold time, and cooling segments were completely lost. My kiln has thick fire brick and takes all night to cool to room temp., so there must have been just enough heat to keep this piece from shattering. Lesson learned ~ don't program a firing schedule when over-tired and suffering with a throbbing headache. I usually double check and sometimes triple check my programming, but this time I didn't. I welcome any tips you might add to Bert's for a successful re-firing.

I hope you don't think your the first to hit a wrong button while programing, your not, we have all done the same thing. With Bert's advice all will work out, the piece is not lost.
bob

[Carrie Loosz]

Thanks for your kind words, Bob. I feel much better knowing that.

[Bert Weiss]

When I visited Murano, I went to several glass factories for their tour. I was very surprised to see that in every factory, they used a "garage" for an annealer. This was a large brick chamber that sits all day around 900ºF At the end of the day, they shut off the heat, and everything anneals overnight with no added power.

There is a significant difference between the work made there and what we do. There only a small percentage of each glass piece is sitting on a shelf, Most of the piece is open to the air. This is a much simpler anneal challenge than a flat slab of glass sitting on a shelf, where half of the surface are is either in contact with a hard shelf or an insulating shelf.

I have a math formula for figuring out relative soak times for different thicknesses. The time the formula yields for 1/4" is so short, that I add a bit of time for my practice.

This is why I think you will be OK.

[Carrie Loosz]

That's very interesting, Bert, and good to know your thoughts regarding your math formula for 1/4" thick fused glass. I followed your advice in your earlier reply and opted to go ahead and fire the piece again. I decided to slowly take it up only to fire polish temps this time as it's already fused flat. With proper annealing, I won't have to worry about it suddenly breaking in my friend's home. If this wasn't a gift, I would have just let it sit in my studio to see what would happen down the road. Thanks again.