Bubble Squeeze Education

[Judd]

Please educate me. On the ramp up after a brief pause at 1000, I've seen this for the bubble squeeze:
50 to 1250 hold 60
I don't understand why that's adequate for a bubble squeeze. If the glass is textured, even after adding chads on the 4 corners, you'll still have bubbles. If the glass is flat, the bubbles would still be trapped because 1250 is too cold for the bubbles to rise to the surface. Putting chads on the 4 corners of flat glass would give your 4 bubbles on 4 corners.

Am I over-thinking this? Just curious. Thanks.

[Morganica]

Yes and no on the overthinking. The idea is not to have the bubbles rise THROUGH the glass, but rather to push the air from between the components and out the sides of the layup. (that's the "squeeze" part) That way, when the glass softens and comes together there's less air to trap and fewer (hopefully no) bubbles.

The idea with the chads is to elevate the edges so that they have farther to fall than the center. Therefore, the center glass pieces come together first, increasing the likelihood that they'll push aside the air and, again, it'll escape through the sides before they come together completely. A bubble squeeze may not fully remove the bubbles, but it certainly lessens them.

If the glass is textured, you may trap air where the highest points of texture touch down first, but again, the idea is that you're still giving the air escape routes prior to the glass fully touching. You can get bubbles around the chads, but more likely the problem is you change the color density where the chads contact the glass, so it looks a bit different.

If I'm that worried about bubbles I'll make my blank about an inch larger than the final dimension, chad it up and do a long bubble squeeze to remove air from the important part of the piece. After fusing I cut out the final shape, and remove any bubbles, discolorations, devit, whatever...because it's usually going to be at those edges.

[S.TImmerman]

So very helpful !!!!!