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I've done alot of bottles in my old kiln but now that I have a larger one I wanted to try a BIG bottle. I tried a bar sized Grey Goose bottle that has the thick bottom and THOUGHT everything was ok, but the bottoms keep breaking off. The break is where the bottom flops over and is thicker. I'm sure it must be an annealing issue so how long should I hold it?
I usually hold at 1025 for 30 minutes.
I've checked the archives but couldn't find anything to do with thick bottomed bottles.
Thanks for the help
Diane

How thick are the bottoms after slumping? I think 30 min may be too short.

Diane wrote:I've done alot of bottles in my old kiln but now that I have a larger one I wanted to try a BIG bottle. I tried a bar sized Grey Goose bottle that has the thick bottom and THOUGHT everything was ok, but the bottoms keep breaking off. The break is where the bottom flops over and is thicker. I'm sure it must be an annealing issue so how long should I hold it?
I usually hold at 1025 for 30 minutes.
I've checked the archives but couldn't find anything to do with thick bottomed bottles.
Thanks for the help
Diane

At the bottom, the thickness is at least 0.6 inches thick.
hold for 45 min. and then 100 deg/hr down to 800 deg.

Jim

Diane,
I just did a finlandia bottle last night.
I usually drop to 970 and hold for 40
then cool to 875 hold 40, then 775 for 40 and off.
This is probably not all needed but it doesn't give me any problems.

Give it a try


Michael
Happy slumping

Diane wrote:I've done alot of bottles in my old kiln but now that I have a larger one I wanted to try a BIG bottle. I tried a bar sized Grey Goose bottle that has the thick bottom and THOUGHT everything was ok, but the bottoms keep breaking off. The break is where the bottom flops over and is thicker. I'm sure it must be an annealing issue so how long should I hold it?
I usually hold at 1025 for 30 minutes.
I've checked the archives but couldn't find anything to do with thick bottomed bottles.
Thanks for the help
Diane

Diane

I never slumped a bottle. If your heavy glass is 1/2" thick I would hold it for 2 hours at soak and take 2 hours to go down 100º 1.5 hr the next 200º and 1.5 hr the next 400º.

The soak temp is determined by a slump test. Soak 100º below slump temp. I have no idea what that temp is, but I can tell you that if you are spending time at the wrong temp it is totally wasted.

To do a slump test on a bottle, you would have to saw a 1" wide strip up to 12" long and stick it between 2 bricks. Place another brick at the end so you can see when it moves. bring the glass up to a temp below slump, hold for 20 - 30 minutes and go up 10º. Do this until the strip moves.

Follow that procedure and you are good until your thermocouple craps out.

This test works for all kinds of glass except for low expansion borosilicates that are more forgiving.

I recently fired two wine bottles, 2 different firings. I had the same type bubble at exactly the same place in both bottles. I fired 600 to 1200, held 30 mins, fast to 1500 on one and 750 to 1500 on the other firing. Any suggestions? Linda

Linda, wine bottles with a shoulder (rapid widening) below a narrow neck always get a bubble between the layers of glass in the shoulder area when the neck seals off before the body of the bottle flattens. Bottles with a gradual taper from bottom to top without a shoulder under a neck do not have this problem.

Best wishes,
Tom in Texas