Slumping problem.

[Sherry R]

I'm wondering if someone have a suggestion of what I could do to salvage a piece.
I full fused a 6 1/2 piece with 2 pieces of 96. Then I slumped it into a 6 1/2" square mold. It was a mold with about a half inch drop and a 1 1/2" lip. My slumping schedule was:
300 - 1100 - .20
150 - 1250 - .25
9999 - 950 - .60
150 - 700 - .00

When I opened the kiln this morning, the left side of the piece pulled in but the rest of the sides were straight. I slumped with the top element, so it should have had the same heat for the piece. If I reslumped it, what would that do?

I took a picture with my cell, but the file is too big to download. I have used this schedule before and no problems.

[Morganica]

If I had a dime for every time someone said "I used this before with no problems...." I'd spend about half of it on a 1957 Ferrari Testarossa and a really good-looking Italian mechanic...

There are a lot of reasons why a schedule might have worked last time but didn't do what you expected this time. Usually it's because the two situations aren't really identical:

--The glass could be different--different colors, thicknesses and forms of glass can behave differently with the same schedule
--The mold could be very slightly uneven--if one area of glass gets a headstart slumping in the mold it tends to throw everything else off
--The mold could be differently shaped or sized--smaller molds can be more difficult to slump in (well)
--The glass could have been positioned slightly off-center on the mold, or possibly jostled when the lid closed
--The mold might not have been exactly centered under the elements

Personally, I don't like to go much faster than 200dph on the ramp up in a slump--the slower heat-up seems to be gentler on the glass. I don't really see the need to hold at 1100; instead of doing that I'd probably go 200dph to your slumping temp and stay there.

But I don't think your schedule was out of line. I think I'd look at the other possible factors I mentioned, see if any of them could be the cause.

[Bert Weiss]

If I had a dime for every time someone said "I used this before with no problems...." I'd spend about half of it on a 1957 Ferrari Testarossa and a really good-looking Italian mechanic...

Love that Cynthia, we could have a road race!

Another interesting factor is that a full sheet of 96 glass is not a uniform thickness. The sheets tend to be thinner in the middle. So, if you happen to use 2 thinner than 3mm pieces of glass, the tendency to dogbone will be much greater. It is even possible that one side of your construction is thicker than the other. 96 sells by the square foot, and this is one of the hidden factors why, even though it costs less than other glasses, there are reasons why it is worth less.