Large Bubbles - WarmGlass.com

Large Bubbles

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Cathy C
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Joined: Sun Nov 18, 2007 9:27 pm

Large Bubbles

Postby Cathy C » Sun Dec 16, 2007 10:03 am

I am new to the fusing world and have only had minor luck with any glass project. I have started to use fiber paper because kiln wash stuck to the back of the glass and I had large bubbles with break through. This was with single layer glass and frit or smaller pieces. I just tried my first piect with 2 layers of 11" diameter glass and fusing paint in between. I paint fused per the instructions. While full fusing I slowed my temp increase between 1100 and 1240 per all the info I have gathered. The result is a few large bubbles between the layers. Is there anything that can be done to salvage the piece? Like reheating, etc...

Any input will be greatly appreciated.

lucho/lachezar/
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Re: Large Bubbles

Postby lucho/lachezar/ » Sun Dec 16, 2007 10:16 am

Your firing program, please. And what type of enamels? Glass, too...

Cathy C
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Joined: Sun Nov 18, 2007 9:27 pm

Re: Large Bubbles

Postby Cathy C » Sun Dec 16, 2007 11:27 am

I used Spectrum 96 white with Glassline crimson paint for the bottom layer and clear spectrum 96 for the top layer. First I did a paint fuse @ 1100 degrees with no top layer per the instructions from the person who sold me the paint. My second firing schedule for this project was 350 to 1425, hold 20 minutes, 120 to 1050, hold 30, 100 to 750.
My kiln seems to fire hot. Previous firings I had fired 300 to 750 and full fire to 1425 with a 20 minute hold.
I have been reading the book Warm Glass and my kiln instruction manual and looking on this bulletin board to come up with a firing schedule.

Deb Lewis
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Re: Large Bubbles

Postby Deb Lewis » Sun Dec 16, 2007 2:07 pm

When I use glasslines I fire uncovered to at least a tack fuse temp, sometimes more. When I add the top glass I add a bubble squeeze as usual. You are probably trapping regular bubbles by going to fast. Your top glass is sealing at the edge before the bubbles can find a path out. Try slowing down from 1000 to around 1150 going at 50 degrees per hour and hold for 30 minutes at 1150. That should help the bubbles find a way out.

Your second schedule is all wrong. 300 to 1000 (or slower!) 50 to 1150 hold 30 AFAP to 1000 hold 8-10 (per Spectrum site) 200 to 950 hold 40 100 to 700 no hold (for brick kiln), off if your kiln holds heat well. (Many people skip the hold at 1000 with no problems.)

Uhh, I just saw your first schedule. Sorry, but it's needs some help. You don't need to hold at 750-go straight to 1000. Full fire from there is asking for problems, even with a single layer. With a single layer (you don't mention the size) I'd fire from 1000 at 300-400 per hour to top temp. Your top temp is ok if that works for you and gets the look you want.

This all, of course, is my opinion and I'm sure with time you'll see others. The best course is to try different things and keep good notes of what worked and didn't work. Eventually you'll have a nice set of programs that can give you what you want when you want it.
My goal in life is to be the kind of person my dog thinks I am.

Barbara Muth
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Re: Large Bubbles

Postby Barbara Muth » Sun Dec 16, 2007 3:04 pm

In the first firing with the single layer if you are getting any dogboning that may be why you are trapping air in the second firing. Read here in the archives about bubble squeeze schedules (I've written about them countless times). You need to slow way down between 1050 and 1250 if you want the air to escape before it is trapped.
Barbara
Check out the glass manufacturer's recommended firing schedules...
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