Fusing glass to texture mold without bubbles forming - WarmGlass.com

Fusing glass to texture mold without bubbles forming

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Fusing glass to texture mold without bubbles forming

Postby Ladyphoto » Mon Oct 28, 2013 2:55 pm

Forgive this long post, but I need help fast.

I'm relatively new to kill forming. I've got an art exhibit opening the Friday night and things coming out of the kiln have bubbles. I'm in a panic. Specifically, one texture mold in particular is creating lots of bubbles that when I slump the piece in a slump mold, they burst and make craters.
I'm using a Fleur d'Lis mold that is 7" X 13". I put a piece of Bullseye amber glass on the bottom, and have tried two different types of COE 90 clear glass on top. Both made bubbles, but the Uroboros glass (90 COE supposedly compatible with Bullseye) that a salesperson told me didn't make bubbles as badly as Bullseye clear made even larger bubbles. I think the texture tile is made by Creative Paradise, so I used their firing schedule below:

Rate 1 - 300 Temp 1 - 1360 Hold 1- 20 minutes
Rate 2 - 300 Temp 2 - 1465 Hold 2 - 1- minutes
Rate 3 -9999 Temp 3 - 960 Hold 3 - 60 minutes
Rate 4 - 100 Temp 4 - 825 Hold 4 - 0 Minutes

I'm thinking that the mold is the problem in that it has so many ups and downs - it is tiled with a number of raised fleur d'Lis'.
One other fusing onto a tile with patterns not nearly as high seemed to do fine.
The problem is that I live in Saints territory and I think that these trays would do well, and besides, I really like it. Plus, the first mold broke so I use half of it for small plates and bought a new one for larger trays. I've got quite an investment in those molds. They would be so pretty if they didn't have holes and if I knew what I was doing.

Does anyone have any ideas as to what I could do to reduce or eliminate these large bubbles? Also, with the piece that has the bubbles that haven't popped into craters, should I drill them and hope that the glass slumps back into the craters while slumping on my slump mold?
photo 3.JPG
Photo of slumped tray with bubbles that burst when slumping. I think it also devitrified, whatever that means
photo 2.JPG
Close-up of bubbles
photo 1.JPG
Full tile with huge bubbles

Brad Walker
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Re: Fusing glass to texture mold without bubbles forming

Postby Brad Walker » Mon Oct 28, 2013 3:19 pm

Prefire the two pieces of glass together, using a full fuse schedule. If you don't already, add a bubble squeeze (30 minute hold on the way up) at around 1250F. You'll get small bubbles, randomly spaced.

Then put the pre-fired piece on the mold and fire again. No new bubbles, just the small ones, which shouldn't ruin the appearance of your final piece.

Valerie Adams
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Re: Fusing glass to texture mold without bubbles forming

Postby Valerie Adams » Mon Oct 28, 2013 5:35 pm

You'll get fewer bubbles using Bullseye's Tekta instead of Uroboros clear, which is machine rolled and very smooth.

The slight texture of the Tekta allows air to escape, resulting in fewer bubbles. I've got side-by-side comparisons which show larger, irregularly shaped bubbles with Uro and nice, tiny champagne bubbles with Tekta.

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Re: Fusing glass to texture mold without bubbles forming

Postby Morganica » Mon Oct 28, 2013 8:12 pm

I would prefire the blank also, with the bubble squeeze. Depending on your kiln you might want to make it a little bit lower than 1250F (in my kiln, for example, 1250F is too hot, it needs to hold around 1230). I'd also slow down the upramp from about 1000 degrees on, to something like 150/200 dph, to give the glass a little more time to settle.

You're still liable to trap bubbles in that tile, especially if there are ridges or furrows between the rows (as it looks like there might be). Try a test with a prefired 6mm blank and see.

If you still get bubbles around the fleur-de-lys shapes, try chadding the corners. IOW, place small squares of glass right under the corners so that the glass is suspended about 3mm above the mold. When the glass softens on the upramp, it will drop at the point farthest from the chads (i.e., the center) and spread out towards the chads, pushing the air ahead as it goes. That will reduce bubbles. Try it, and see if it works better for you.

Are you planning to cut these into individual tiles?
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Re: Fusing glass to texture mold without bubbles forming

Postby tbach » Tue Oct 29, 2013 7:39 pm

I purchased two other texture tiles from Creative Paradise - haven't had the slightest problem with them using either 6mm thick piece of glass or prefired 6mm blank (two 3mm pieces of Bullseye or Uroboros 90 that I fire to full fuse with 45 minute bubble squeeze at 1250°- I also have found that I can effectively control the size of between layer bubbles by sifting a very fine layer of clear glass powdered frit between my two layers. I don't think it changes the amount of bubbles . . . that's just part of fusing . . . but it definitely makes those bubbles smaller, and I hardly ever get those nasty surface bumps when I remove fully fused blank from the kiln. Since I often screenprint designs on glass surface, it needs to be as flat as possible.

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