1137 amber problem - WarmGlass.com

1137 amber problem

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Terry Ow-Wing
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1137 amber problem

Postby Terry Ow-Wing » Tue Dec 09, 2003 3:08 pm

Has anyone had problems with 1137 amber?

THis is a picture of a plate design that I have been making for at least 2 years. I have now 4 cracked plates. I have used this design in two different kilns and the amber always cracks. I have the same exact design but without the amber glass and have fired it at the same time and the other platters always made it. It is cracking before my kiln reaches 500 degrees. I am ramping up at 450 degrees / hour. the size of the plate is 15" x 15". The batch on one of the sheets is 80403. The other sheet of glass I do not have the information. Of course I have my last show of the year this weekend and a huge commission where I need it.....ahhhhh! :cry:

http://www.acga.net/terryow-wing/1137.html
Last edited by Terry Ow-Wing on Tue Dec 09, 2003 4:08 pm, edited 1 time in total.
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Barbara Muth
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Postby Barbara Muth » Tue Dec 09, 2003 3:29 pm

Terry that sounds a bit like what happened to me this summer. All of a suddent he schedule I had been using forever with some of my glass wasn't working. I say schedule because I looked at everything else. It has to do with the dark glass absorbing the heat faster than the light glass. Anyway, I was ramping up at 300. Now I ramp at 200 and no more cracked pieces. At BE they told me that I had been lucky thus far and my luck had run out. I was probably working at the limit of what the glass would take. Try slowing that ramp down.

Barbara
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Check out the glass manufacturer's recommended firing schedules...
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gone

Postby gone » Tue Dec 09, 2003 3:48 pm

Hi Terry,

450 degrees/hr isn't fast at all for a first firing. It does seem like your amber is "touchy", especially since you've been doing the design for 2 years without problems. Did you contact Bullseye already? They're good about solving problems like this. Maybe you could still ramp very slowly and have it survive. As for the current piece, the cracks are in a cool pattern. You could fill the gaps with frit and have a nice piece for the show.
Sorry this happened to you, the timing is terrible!

Terry Ow-Wing
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Postby Terry Ow-Wing » Tue Dec 09, 2003 4:04 pm

and you know this only happens right before a show!! The other design was the clear with stringers in the middle part and I fired it in the same kiln at the same time with the amber design and they are fine....oh well it's in the kiln again at 200

crossing my fingers! :roll:
Terry Ow-Wing Designs
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Terry Ow-Wing
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Postby Terry Ow-Wing » Tue Dec 09, 2003 4:07 pm

Els VandenEnde wrote:Hi Terry,

450 degrees/hr isn't fast at all for a first firing. It does seem like your amber is "touchy", especially since you've been doing the design for 2 years without problems. Did you contact Bullseye already? They're good about solving problems like this. Maybe you could still ramp very slowly and have it survive. As for the current piece, the cracks are in a cool pattern. You could fill the gaps with frit and have a nice piece for the show.
Sorry this happened to you, the timing is terrible!


Yup have my question into BE but their tech person will not be in till 3:00. I've done the fill in the gap design and I actually really like it but since I have a huge cutom order coming up I want to be sure of what is going on.Right now I'm going into my 5th show in a row and I'm dead tired - just even turn down a visit by aclient to my studio - I'm running on fumes now....
Terry Ow-Wing Designs
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Lani McGregor
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Postby Lani McGregor » Thu Dec 11, 2003 4:53 pm

Terry,

I absolutely LOVE that the internet lets us actually SEE the problems. I read yours and scratched my head a bit, then opened the image and bingo.

This is a textbook example of thermal shock:

Unless I'm not reading the picture properly, your base glass is a 15" x 15" sheet of 1137 amber transparent.

On top of that you've placed a border of opaque irid.

Glass is an insulator. The center part of your base amber sheet is getting heated DRAMATICALLY differently (more rapidly) than the areas that are covered by the insulating (and reflecting - even worse) border glass.

I am STUNNED that a 450F/hr heat up has ever worked for you. The kiln goddesses must ADORE you. I'd be afraid to fire this kind of a lay-up faster than 100F/hr... but every kiln is different and if this has ever worked for you, your kilns a much more blessed than ours.

Sorry for the problems.... sleep also helps..... -Lani

Terry Ow-Wing
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Joined: Sun Mar 09, 2003 3:21 pm
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Postby Terry Ow-Wing » Thu Dec 11, 2003 6:29 pm

Lani McGregor wrote:Terry,
....

Glass is an insulator. The center part of your base amber sheet is getting heated DRAMATICALLY differently (more rapidly) than the areas that are covered by the insulating (and reflecting - even worse) border glass.

I am STUNNED that a 450F/hr heat up has ever worked for you. The kiln goddesses must ADORE you. I'd be afraid to fire this kind of a lay-up faster than 100F/hr... but every kiln is different and if this has ever worked for you, your kilns a much more blessed than ours.

Sorry for the problems.... sleep also helps..... -Lani


What really stunned me is that I've been doing this for at least two years and 2nd I have the same design fired side by side with the amber - but using the clear with black stringers - it has been fine. I knew it was some kind of themal shock - but it caught me by surprise. The only other detail I can think of is that on the amber the irid is on top while with the clear with black streamers the irid is on the bottom. Oh well - did the same design with the amber and slowed it down to 250/hour and it's fine. Just for reference I have a 9" deep coffin style kiln and a 20 x 20 paragon front loader.

Guess those speedy ramps catch up sooner or later.
Terry Ow-Wing Designs
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