is how hig do I have to fire to break the bubble??? Or any other suggestions, please... Yes I have checked with the archives. Thanks in advance ,Pam,bubble problems
Moderators: Brad Walker, Tony Smith
bubble problems
Another problem with my beautiful blue/purple opal glass. I fused the broken cirlcle with cut out pieces of a large Kokopelli playing his flute to a dicro. moon. I filled in the broken line with frit. Well, it worked but needed to fill in one small point. I got the great idea to cap this baby with clear, what I got was one giant bubble at the edge of the moon. I fired 300dph to 1250 held for 3o minutes, AFAP to 1375 held for 1 hr. , ASAP to 960 hold for 30 minutes. My guess is I ramped to fast, didn't hold long enough.... and go big bubbles. My is how hig do I have to fire to break the bubble??? Or any other suggestions, please... Yes I have checked with the archives. Thanks in advance ,Pam,
is how hig do I have to fire to break the bubble??? Or any other suggestions, please... Yes I have checked with the archives. Thanks in advance ,Pam,About a year ago someone posted that they always ramp 300 d/h to the end temp in order to avoid bubbles. I usually do so, and rarely have any bubbles. Recently, I tried a schedule exactly as listed from Spectrum, which had a slow ramp to about 1000F, then AFAP to fuse temp, etc. and this gave me a ton of bubbles on my pieces. I then re-fired the two pieces (6 inches square with 2.5 layers) using my more typical schedule, in this case 300F d/h to 1425F hold 30, AFAP to 955 hold 30, 200F d/h to 750F. This levelled the bubbles in both pieces.
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Jerry
Bubbles
Suzan is onto something.
Do what you need to so that you get to about 1100 degrees and then SLOW DOWN! That's where the bubbles will form if you go too fast. Another element to consider should you go to 1500 or so is the thickness of your piece. Thin pieces will bubble while thicker ones typically do not.
In any case, above about 1100 degrees, if you go fast you are in danger of bubbles forming regardless of what Spectrum believes.
Jerry
Do what you need to so that you get to about 1100 degrees and then SLOW DOWN! That's where the bubbles will form if you go too fast. Another element to consider should you go to 1500 or so is the thickness of your piece. Thin pieces will bubble while thicker ones typically do not.
In any case, above about 1100 degrees, if you go fast you are in danger of bubbles forming regardless of what Spectrum believes.
Jerry
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Cynthia
For smaller bubbles, Suzan has the right fix. If your bubble is rather large, pea sized or larger, I think you have a few more issues. If you break it and re-fire, you will still see where it was (it will leave a scar). If you try to fire high enough that it bursts, you still see where it was. To do that you will want to go to 1550 perhaps, watch it and see when it bursts. The other problem with that though is that you will bring other bubbles to the surface and now you have another set of problems.
You can try to incorporate the bubble boo boo into the design. Sometimes you can break the bubble, cut out the bubble area, add new design elements to that area and refire. Dependent upon your design and where the bubble is will determine if that can be done. You can try to fire out the bubble and recap the top to see if you can obscure the scar. Lots of fix options, but only testing them out will tell if they succeed.
From now on, fire as the others have suggested if you want to decrease trappin air bubbles in the glass. Don't ramp AFAP to a full fuse, but ramp up at 300 to 500 dph to full fuse. Full fuse will be the temp you reach when the piece is fully fused (different in your kiln, different glasses)...then no soak and down to anneal. Watch and record your firings and schedules and you'll learn what that top temp will be.
Good luck.
You can try to incorporate the bubble boo boo into the design. Sometimes you can break the bubble, cut out the bubble area, add new design elements to that area and refire. Dependent upon your design and where the bubble is will determine if that can be done. You can try to fire out the bubble and recap the top to see if you can obscure the scar. Lots of fix options, but only testing them out will tell if they succeed.
From now on, fire as the others have suggested if you want to decrease trappin air bubbles in the glass. Don't ramp AFAP to a full fuse, but ramp up at 300 to 500 dph to full fuse. Full fuse will be the temp you reach when the piece is fully fused (different in your kiln, different glasses)...then no soak and down to anneal. Watch and record your firings and schedules and you'll learn what that top temp will be.
Good luck.
The one above the moon is about the size of a quarter. I'll try and post a photo. Pam-
Geri Comstock
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- Location: Northern CA
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Squeeze technique
To minimize the bubbles in your glass, you need to use the squeeze technique...I believe it's called that because glass blowers started doing something they call "squeezing" glass to remove the bubbles.
I think Gil Reynolds coined this term in an article he wrote for Spectrum about the process.
Anyway, the exact "recipe" for doing this depends on the glass you're using and your kiln.
For BE glass, in my kiln, with a clear machine-rolled base plate and a number of smaller pieces in a combo of transparents and opals on top, I "squeeze" the glass at 1180 for 30 minutes. That just means to heat the glass to 1180 at your normal ramp rate and hold it there for 30 minutes.
This "squeeze" eliminates many of the bubbles I used to get...it's not completely bubble-free, but the bubbles are very small and barely noticeable.
Others that I've given my squeeze schedule to have had to adapt it to their kiln and the glass they're using, which have been different from mine. But this should give you a starting place for experimenting. People have told me they've had to raise or lower the squeeze temperature and increase the hold time in their kilns to get the results they want.
Others, like Brock, use the "chad" technique, where they position small pieces of glass on the edges between two layers to allow the air to escape. I've never used this technique so I can't describe it. A search in the archives for "chad" and "bubbles" should find some posts that explain the details of the process.
Good luck!
Geri
I think Gil Reynolds coined this term in an article he wrote for Spectrum about the process.
Anyway, the exact "recipe" for doing this depends on the glass you're using and your kiln.
For BE glass, in my kiln, with a clear machine-rolled base plate and a number of smaller pieces in a combo of transparents and opals on top, I "squeeze" the glass at 1180 for 30 minutes. That just means to heat the glass to 1180 at your normal ramp rate and hold it there for 30 minutes.
This "squeeze" eliminates many of the bubbles I used to get...it's not completely bubble-free, but the bubbles are very small and barely noticeable.
Others that I've given my squeeze schedule to have had to adapt it to their kiln and the glass they're using, which have been different from mine. But this should give you a starting place for experimenting. People have told me they've had to raise or lower the squeeze temperature and increase the hold time in their kilns to get the results they want.
Others, like Brock, use the "chad" technique, where they position small pieces of glass on the edges between two layers to allow the air to escape. I've never used this technique so I can't describe it. A search in the archives for "chad" and "bubbles" should find some posts that explain the details of the process.
Good luck!
Geri
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Tony Smith
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- Joined: Sun Mar 09, 2003 5:59 pm
- Location: Massachusetts, USA
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If the bubble is thin, you can try breaking the bubble out then covering the area with clear frit and taking it back up to a full fuse. Hold at 1480° until the frit levels out... probably 20 minutes or so. Keep the area under the bubble as clean as possible (this means no sandblasting or grinding or toolmarks) otherwise you'll see the scar.
Tony
Tony
The tightrope between being strange and being creative is too narrow to walk without occasionally landing on both sides..." Scott Berkun
Bubbles
I have found that as much as I hate to slow down it is the only way to go. Mu current schedule is uuslly 400 to 1100 soak 10 min. 60dph to 1280 soak 25 min then 400dph to final temp. Since doing this rather conservative schedule I have not had any bubbles at all. I usually put a small chip under the bottom layer to allow air to escape from the shelf and the glass. I hardly ever fire on paper anymore. Tom I tried what Tony suggested with poping the bubble and put clear frit in. It worked but you could see a slight ring mark where the bubble was. Tom 
Good new,at least it looks that way. Thank-you all for your advise. I popped the bubble by scoring it and soing a little tapping. Refired very, very slow, and this morning before leaving for school I took a peek. The area where the big bubble was looks fine, at least for now, kiln at 700. Guess, I've learned my lesson. I'll sitll try and take a photo tonite to let you all see my plate. Thanks again. Pam 