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bubbles

Posted: Thu Oct 29, 2015 10:34 am
by AJK25
I am getting bubbles between layers of glass when I fuse Bullseye glass. I have tried a "bubble squeeze," but it hasnt helped. Just wondering if anybody has any thoughts or suggestions.

I am fusing 3 layers of glass -- Bullseye Clear Reed on top, and then either aqua tint, white or black as the bottom 2 layers. I think that the problem is occurring because the glass isnt completely flat (because it's hand rolled). And thus, is causing bubbles to occur between the layers. These bubbles really look bad in this design. I believe Spectrum glass is machine rolled, and thus, flatter, and this might solve the problem. But they dont make Reed glass, so i can't use their glass.

Re: bubbles

Posted: Thu Oct 29, 2015 10:48 am
by linn keller
bullseye glass manufacturing does not automatically = bubbles. so, the question becomes what is...
if you post schedule, layup, pics (before and after are good), you'll likely receive answers that will be helpful.
without something more than "bubbles" accurate diagnosis is really not feasible.
linn

Re: bubbles

Posted: Thu Oct 29, 2015 12:26 pm
by Valerie Adams
Spectrum (or any completely smooth, flat glass like Uroboros Machine Rolled) is more prone to bubbles if you're not using a good bubble squeeze because lack of texture means there's no room for air to escape.

You'll need to post your schedule so people can help trouble shoot.

Some people find sifting a single layer of powder between layers helps to minimize bubbles. Bullseye has a tip sheet about this called Powder Power:
http://www.bullseyeglass.com/methods-id ... power.html

Re: bubbles

Posted: Thu Oct 29, 2015 7:25 pm
by DonMcClennen
We can't help you when we don't have your schedule and build-up. There was a recent poster who thought a bubble squeeze was simply holding at 1250F. Do you use chads?? do you slow down to 50F degrees per hour from 1100F up 1250F ... help us help you!

Re: bubbles

Posted: Fri Oct 30, 2015 12:37 am
by Peter Angel
I've had a lot of luck sprinkling a few grains of clear powder frit between the layers of glass, especially the corners. You get fewer bubbles. But only a tiny sprinkle of frit - less is more. Pete

Re: bubbles

Posted: Sat Oct 31, 2015 3:02 pm
by Morganica
And posting a picture of your layup before fusing, and the result after, will also help. There are MANY reasons for bubbles, and a few different types of bubble formation as well. There are also many ways to do a "bubble squeeze," so simply using the terms isn't really going to help us figure out the problem--we need a whole bunch more information and images.

So...let's start with how you set up your piece, and what the piece actually looks like first. Then we'll get into how to fix it, and whether or not a particular brand/color/style of glass is the culprit. Usually there's a way around most of those things.

Re: bubbles

Posted: Mon Nov 02, 2015 5:00 pm
by AJK25
I am so incredibly sorry for not responding. In the past, whenever somebody responded to me, it sent me an email telling me so. And i didnt receive any emails this time, so I assumed that nobody responded. I just logged on to warmglass.com today just to make sure, and i saw everybody's responses. Thanks to all of you.

This is the firing schedule that i used:
500 degrees/hr to 1100 degrees. No hold
300 to 1175. Hold 25 min
300 to 1390. No hold
AFAP to 960. Hold 1.5 hrs.
75 to 750. Turn off kiln

Attached are photos (post fire). It's just one layer of Bullseye Clear Reed on top of a layer of Bullseye aqua tint, on top of Bullseye light peach cream. Bubbles are between the clear reed and aqua tint.

Thanks!!

Re: bubbles

Posted: Mon Nov 02, 2015 5:18 pm
by Brad Walker
AJK25 wrote:I am so incredibly sorry for not responding. In the past, whenever somebody responded to me, it sent me an email telling me so. And i didnt receive any emails this time, so I assumed that nobody responded.


At the bottom of the box when you post are a bunch of check boxes. One of them says "Notify me when a reply is posted." If you check that box, you'll get a reply when someone posts.

Re: bubbles

Posted: Mon Nov 02, 2015 7:16 pm
by AJK25
thanks Brad. It's actually checked. Not sure why they aren't coming through. But no worries. I can just logon and check myself.

Re: bubbles

Posted: Tue Nov 03, 2015 12:46 am
by Morganica
Thanks. First, are you putting the reeds (the raised lines) to the inside or the outside of the layup?

BTW, there's an exceptional Bullseye tech note about just this subject that you should read: http://www.bullseyeglass.com/images/stories/bullseye/PDF/TechNotes/technotes_05.pdf I think that will give you quite a bit of information.

I think that, more than likely for your kiln/schedule/layup, your schedule is either too fast or your piece is too close to the elements in the kiln. It looks as though the edges of the piece are sagging and sealing over long before the air has been pushed out, so the piece traps bubbles.

What you're really trying to do with a bubble squeeze is to slow the rate at which you're putting heat energy into the glass way down so that it's heating up very evenly. That way the glass starts to sag from the open, unsupported areas first, pushing out the air until it escapes out the edges. Sometimes, to ensure you give the air enough room to get out, you can also "chad" the edges, i.e., prop them up on small squares of scrap glass to ensure that the air has extra-large escape tunnels.

So...1175 is within the bubble squeeze range, but it may not be hot enough in your kiln, at that schedule. You've got 500dph to 1100, then 300 to 1175 with a 25 minute hold. I tend to do my bubble squeezes around 1200-1225F, hold for 30 minutes to an hour, depending on what I'm after, and that's after I've come up from 1100F at 150dph. I'm giving the glass quite a bit more time to heat up and get soft.

You might experiment a bit with slowing down the temperature after you hit 1100, trying a little a little hotter temp, etc. Depending on how close the piece is to your kiln's elements, you may also need to "baffle," i.e., use dams and fiber paper to insulate the piece. In a smaller kiln where you can't avoid getting the glass very close to the kiln elements, bubble squeezes can be more difficult.

And if you really have trouble, try chadding or clear powder (or some of the other suggestions in that tech note).

Re: bubbles

Posted: Tue Nov 03, 2015 10:23 am
by AJK25
the reeds are on the outside of the layup.
Thank you so much Morganica. I will try these suggestions. Very helpful!!!