Re: Design Question
Posted: Sat Jan 26, 2008 6:02 pm
It's probably worth testing a few times to see what works best for what you have in mind. You can most certainly make pieces with a single 3mm layer of glass--I do it all the time--or even with a single layer of thin glass. This piece, for example, is 20 inches in diameter, made on a single layer of 3mm topped with pieces of thin glass, stringer, powder, and confetti. It varies in thickness from 3-4mm.
HOWEVER...I also carefully controlled the firing and stayed at "process temperatures" for as short a time as possible, heading back quickly to the anneal soak down the minute I saw it had flattened sufficiently. This piece is about 7 years old and I don't have any firing notes, but I suspect that the top temp was around 1440F. I was also (deliberately) doing this on BE White, a relatively stiff glass, with thin, quickly melting components.
The longer the glass sits at fusing temperatures, the more it's going to draw in on itself, trying to become 6mm thick, and that's when you start having problems with bubbles, holes and what's called "dog-boning," i.e., the piece pulls in less at the corners than in the middles, going from a perfect square to more of a star-shape. In the piece above, the glass HAS pulled in a bit, to do what I call "lipping," slightly thickening the edge for a really nice finished look. Had I left it any longer it probably would have thinned enough to open some holes in the center of the piece.
If you have sufficient decoration on a single layer of 3mm glass to make a total fused height of 6-7mm, without thin spots, you're probably OK--but generally there are gaps between pieces or not enough frit, and if you do a standard full-fuse you'll probably wind up with holes.
It's all about volume control, and Bullseye has a wonderful tech note on their site discussing volume and bubble control, and another about heat and glass, which would probably help you immensely. (In fact, if you're just starting out you might want to head straight to http://www.bullseyeglass.com/education/ and download all the documents you find there...then study them.) And welcome!
The longer the glass sits at fusing temperatures, the more it's going to draw in on itself, trying to become 6mm thick, and that's when you start having problems with bubbles, holes and what's called "dog-boning," i.e., the piece pulls in less at the corners than in the middles, going from a perfect square to more of a star-shape. In the piece above, the glass HAS pulled in a bit, to do what I call "lipping," slightly thickening the edge for a really nice finished look. Had I left it any longer it probably would have thinned enough to open some holes in the center of the piece.
If you have sufficient decoration on a single layer of 3mm glass to make a total fused height of 6-7mm, without thin spots, you're probably OK--but generally there are gaps between pieces or not enough frit, and if you do a standard full-fuse you'll probably wind up with holes.
It's all about volume control, and Bullseye has a wonderful tech note on their site discussing volume and bubble control, and another about heat and glass, which would probably help you immensely. (In fact, if you're just starting out you might want to head straight to http://www.bullseyeglass.com/education/ and download all the documents you find there...then study them.) And welcome!