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Bubble squeeze?

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chgriffin
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Joined: Thu Apr 04, 2013 8:33 pm

Bubble squeeze?

Postby chgriffin » Sun Apr 07, 2013 9:08 pm

I am working with a project that I cannot seem to get all my air bubbles out. The project is an 11 inch bowl. So, I fire my "blank"..... I have a flower in the middle with three small flowers spaced equally around the edge. I am working with Bullseye and capping with Tekta - so three layers. Here is my firing schedule:
300dph - 250 - 20min
300dph - 500 - 30min
300dph - 750 - 40min
300dph - 1215 - 65min
400dph - 1410 - 20min
9999dph - 960 - 45min
I have too much air around the middle element(flower)......and too much around the three on the edges. Suggestions?
Thanks!!
chrys

Morganica
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Re: Bubble squeeze?

Postby Morganica » Sun Apr 07, 2013 9:43 pm

Photo would help.

First, slow down a bit. Instead of speeding from hold to hold on the way up, do 200dph to about 1225 and hold there for an hour. You shouldn't need any holds before then.

Second, without seeing a photo can't say for sure, but the first thing you want to do is make sure your design provides exits to the edges for all components under another piece of glass. if you don't, the bubble squeeze won't matter much.

Third, if you're still having trouble you can chad the edges of your stack--cut some small pieces of glass the same color as the edge of your piece, and place them at the very edges of your piece, in the corners and (if it's long) in the middle). The idea is that the edges will remain elevated until the center has softened and dropped, pushing the air out ahead of it.

If you have a real issue with bubbles, for example because your design is trapping air, you can stack two chads on top of each other for extra elevation.

The trouble with chads is that they distort the edges of the glass so that you may have to do some coldwork to straighten things out again. And they can sometimes leave a mark because they change the volume of the glass at that point, which in transparent glasses can change the color. If I need to chad something, I usually make my piece a bit bigger than the desired final size, so I can trim that stuff away.

Probably the best thing you can do, though, is see if you can fire the base glass with the decoration first, without the capping Tekta. Fuse that flat, and THEN cap and fire again. The piece will be much less likely to trap air.
Cynthia Morgan
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http://www.morganica.com/bloggery
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Laurie Spray
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Re: Bubble squeeze?

Postby Laurie Spray » Sun Apr 07, 2013 10:02 pm

Is there a reason you are not putting the decoration on top of the blanks??? Did I miss something?
Laurie Spray

New website!! Http://bonnydoonfusedglasstools.com
Maker of stainless steel rings,pattern bar formers, pot melt pots, and Bottomless Molds
glass: http://lauriespray.blogspot.com

chgriffin
Posts: 7
Joined: Thu Apr 04, 2013 8:33 pm

Re: Bubble squeeze?

Postby chgriffin » Mon Apr 08, 2013 7:35 pm

Thanks for the suggestions...especially about 200 to 1225. I thought I had allowed space and temperature progression for the air.....but I will give your suggestion a try.

As to why I don't want the elements on top.......ummmmm, just because? :)
thanks again!
chrys

Laurie Spray
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Re: Bubble squeeze?

Postby Laurie Spray » Mon Apr 08, 2013 7:58 pm

Try putting your elements on top.....still do a good bubble squeeze from 1100 to 1250 at 50 degrees an hour

50 degrees an hour 1100/1250 hold 45

Putting the elements between sheets will always cause some bubbles.....



Tryit you'll like it!!
Laurie Spray

New website!! Http://bonnydoonfusedglasstools.com
Maker of stainless steel rings,pattern bar formers, pot melt pots, and Bottomless Molds
glass: http://lauriespray.blogspot.com

RachelM
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Re: Bubble squeeze?

Postby RachelM » Mon Apr 08, 2013 8:57 pm

Cynthia....

Just started laughing when I read your comment starting with "the trouble with chads..." This being said by a Florida girl. :lol:

Very informative answers from you and Laurie. Thanks to both of you!

Rachel Malakoff
Imaglassydiva@aol.com

Morganica
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Re: Bubble squeeze?

Postby Morganica » Mon Apr 08, 2013 9:09 pm

chgriffin wrote:Thanks for the suggestions...especially about 200 to 1225. I thought I had allowed space and temperature progression for the air.....but I will give your suggestion a try.

As to why I don't want the elements on top.......ummmmm, just because? :)
thanks again!
chrys

You can get a bit of depth and magnification if the elements are under a clear cap, it's just a design choice.

The air will expand as it gets hotter, yes, but since the glass isn't going to soften or move much until it's past 1100f or so, holds before then wouldn't help anyway. What you're trying to do with a bubble squeeze is have gravity and the weight of the glass cause the softening glass to gradually come down, pressing the air out of open spaces slowly, before things fuse together. It can't do that if the glass isn't moving.
Cynthia Morgan
Marketeer, Webbist, Glassist
http://www.morganica.com/bloggery
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"I wrote, therefore I was." (me)

LAF
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Re: Bubble squeeze?

Postby LAF » Wed Jun 05, 2013 8:14 am

Laurie, I used your schedule to eliminate the problem with bubbles and it worked great, but I ended up with devit? Any suggestions? Lou Ann

Laurie Spray
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Re: Bubble squeeze?

Postby Laurie Spray » Wed Jun 05, 2013 12:21 pm

Great!!! as for the devit it can be caused by quite a few things....kind of glass, how you clean, using shelf paper with teak, holding too long in the 1300 range......
Laurie Spray

New website!! Http://bonnydoonfusedglasstools.com
Maker of stainless steel rings,pattern bar formers, pot melt pots, and Bottomless Molds
glass: http://lauriespray.blogspot.com

Tracy Fries
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Joined: Thu Jun 14, 2012 7:14 pm

Re: Bubble squeeze?

Postby Tracy Fries » Wed Jun 05, 2013 3:15 pm

Laurie Spray wrote:using shelf paper with teak.....



laurie........what does 'with teak' mean? I probably should know, but.........I don't! Thanks!

Laurie Spray
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Re: Bubble squeeze?

Postby Laurie Spray » Wed Jun 05, 2013 3:23 pm

I meant Tekta clear glass from Bullseye. We do not use it......but if you do .........
sorry I was typing too fast for my own good!
Laurie Spray

New website!! Http://bonnydoonfusedglasstools.com
Maker of stainless steel rings,pattern bar formers, pot melt pots, and Bottomless Molds
glass: http://lauriespray.blogspot.com

Tracy Fries
Posts: 41
Joined: Thu Jun 14, 2012 7:14 pm

Re: Bubble squeeze?

Postby Tracy Fries » Wed Jun 05, 2013 4:16 pm

Laurie Spray wrote:I meant Tekta clear glass from Bullseye. We do not use it......but if you do .........
sorry I was typing too fast for my own good!



Ahhh - interesting. I've been having some devit issues of late - been through the whole rigamarole of possibilities, cleaning processes, type of cleaner, type of rags, firing schedule, opals vs. transparents, la-de-da...........never realized my thin fire/tekta combination might be the culprit??? Hmmmmm..........

Thanks!

BTW....What do you use rather than tekta?

Morganica
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Re: Bubble squeeze?

Postby Morganica » Wed Jun 05, 2013 5:15 pm

It's not so much a Tekta problem as a fiber paper problem. Fiber paper burnoff apparently gives off residues that land on the glass and promote devitrification. I haven't found Tekta to be that much worse than, say, a pale pink opal in this regard.

The way you resolve it is to only use fiber paper in a kiln when you're planning to coldwork the result. Or to remember to vent the kiln until at least 800F to allow the offgassing to escape (i.e., after the paper has turned brown, come back to white and been that way for a few minutes. Or to use fiber when you're going to refire the result with some kind of cap, either more sheet glass, or a thin layer of clear powder.

Or any combination of those three.
Cynthia Morgan
Marketeer, Webbist, Glassist
http://www.morganica.com/bloggery
http://www.cynthiamorgan.com

"I wrote, therefore I was." (me)

Laurie Spray
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Re: Bubble squeeze?

Postby Laurie Spray » Wed Jun 05, 2013 11:47 pm

We use Uroboros rolled clear for 90 fusing...no problems with bullseye shelf paper there!
spectrum clear for 96
Laurie Spray

New website!! Http://bonnydoonfusedglasstools.com
Maker of stainless steel rings,pattern bar formers, pot melt pots, and Bottomless Molds
glass: http://lauriespray.blogspot.com

Tracy Fries
Posts: 41
Joined: Thu Jun 14, 2012 7:14 pm

Re: Bubble squeeze?

Postby Tracy Fries » Thu Jun 06, 2013 11:03 am

Thanks, ladies. I'll be making some adjustments.


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