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Old 04-01-2019, 12:23 PM
Mike Kaplan Mike Kaplan is offline
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Glass is slumping.... why???

Im using Crystallica. I have a clear glass rod that i pulled. I place it in a kiln when its solid and wait to see if it slumps and it does! Why does it slump if the annealing temp is 950F I have two thermal couples on two completely different reading units. Both units are spot on 920F
When the temp goes up as it will go higher to compensate for when i open the door it never gpes higher than 945
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Old 04-01-2019, 12:57 PM
Shawn Everette Shawn Everette is offline
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I've never had Cristalica slump at 950, and although it's not unheard of, a batch off by that much is unlikely to be the culprit. Any time I've had slump issues it's been a kiln malfunction. Bad thermo, bad wire, bad sending unit, bad controller; there are numerous things that could go wrong on a kiln.

Are there any other kilns you can test it on? Any other glasses you can test? What controller are you using?
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Old 04-01-2019, 01:51 PM
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Pete VanderLaan Pete VanderLaan is offline
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you left out bad placement.
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Old 04-01-2019, 05:22 PM
Mike Kaplan Mike Kaplan is offline
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My thermocouple is about 5 from the elements agianst the walls. I have the glass rod in the center of kiln. 1-1.5 feet from the elements.
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Old 04-01-2019, 05:24 PM
Mike Kaplan Mike Kaplan is offline
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I have teated this on more than crystallica with same supposed annealing point and get same results! Im so confused!
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Old 04-01-2019, 05:26 PM
Mike Kaplan Mike Kaplan is offline
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what difference would it make if i use a different kiln if the 2 different thermo reading are the same on this kiln? But i will try that.
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Old 04-01-2019, 06:33 PM
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Pete VanderLaan Pete VanderLaan is offline
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Put the rod on a cantilever in the center of the kiln. Run it up, increasing fifty F at a time once past 900F. Wait 20 min between increases. once it slumps hard, subtract 50 F from that number. Reasonably, that should be the annealing point to use.
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Old 04-01-2019, 07:17 PM
Mike Kaplan Mike Kaplan is offline
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Soonds good
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Old 04-01-2019, 07:28 PM
Rick Wilton Rick Wilton is online now
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The thermocouple wire from the controller all the way to the thermocouple has to be the correct type of wire. You CANNOT use just any kind of wire you may have lying around.

Someone I know recently rewired their annealer with the wrong wire and slumped pieces was the result.
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Old 04-01-2019, 07:55 PM
Eben Horton Eben Horton is offline
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Could have been a high gravity day.
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Old 04-02-2019, 08:43 AM
Shawn Everette Shawn Everette is offline
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Quote:
Originally Posted by Mike Kaplan View Post
what difference would it make if i use a different kiln if the 2 different thermo reading are the same on this kiln? But i will try that.
Usually you are running each kiln on a separate controller, therefore it would give you an indication if something is wrong with that specific kiln vs. the glass being a problem. It sounds like you are trying to run your kiln off a rheostat/thermo readout configuration, and in that case good luck getting any kind of reliable annealing cycle out of it. You can't treat blown glass like boro or moretti and expect great results.

If you are getting the same result from multiple glasses it's definitely the kiln. Without knowing what your actual set up is, it's really hard to diagnose any further than the wire, thermo, or controller is bad. And by bad I mean something is wrong; could be loose connections, could need calibration, could be broken. You placement, without seeing it, for the most part sounds fine.

Also, Eben e might be right. Make sure to take barometer readings and have your shrine to the glass gods pointed due East.
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