To minimize bubbles between
To minimize bubbles between layers of glass:
1) Usually, smooth side to textured side gives the best results.
2) Include a hold 1225F. This is called a “bubble squeeze” and it allows the glass layers to sag and settle against each other before they get “sticky”. This forces out much of the air. When minimizing bubbles really matters to me, I typically hold it hear for 2+ hours (depending on the glass). Thirty minutes to an hour might be more practical and still provides real benefit.
3) If your kiln has side elements, create a heat baffle with kiln furniture/fiber board to reduce the possibility of side heat sealing your edges shut ahead of the rest of the glass fusing together.
4) Consider “chads” – small pieces of frit every few inches around the edge of the bottom piece of glass. Rest the top piece of glass on top of these spacers. When fired, the center of the top sheet will sag first and the area of contact between the two sheets will spread from the middle — pushing the air out as it goes. Make sure the bits are right at the edge – otherwise they will actually cause bubbles as the glass falls around them.
Helios Kiln Glass Studio