I almost hate to ask these questions, but if I don't I'll never know. So here goes!
I want to fuse scraps of glass (yes I know it has to be compatible COE) and cut and form the resulting piece for slumping into a prepared mold. I don't know what keeps the glass from flowing all over the shelf--or does it have a natural tendency to make a free form puddle? Is there a form or some structure I need to put these scraps in first?
The same question would go for millefiori--what keeps the pieces in a recognizable form?
Glass will flow all over the shelf (and possibly drip off the edge) if the average thickness exceeds 1/4". The surface tension of glass tries to keep the thickness 1/4" so it will pull in the edges or spread out to make 1/4" thick. One way to alter this fact of nature is to use dams along or around the edges to keep the glass from spreading and if there is enough glass inside the dams, the resulting glass will end up thicker than 1/4".
Tony
The tightrope between being strange and being creative is too narrow to walk without occasionally landing on both sides..." Scott Berkun
I've used a number of things for dams. The easiest are stainless steel molds made at a metal shop. Mine are about 1" high and I had them formed into circles/squares. It's critical that you line the inside of each mold with 1/8" fiber paper to prevent glass from sticking and cracking. I've had others tell me they've had a problem with glass cracking when they've used the ss, but (if I haven't jinxed myself) I've not had this happen.
You can also take a kiln shelf and have it cut into strips (tile shops can do this if you don't have a tile saw). Form your mold from the cut strips, line the inside again with fiber paper, and place kiln posts along the outside edges to prevent the things from slipping.
Took my new handy dandy MK tile saw and cut up a kiln shelf to make some 8" strips for a dam. I then kiln washed the strips and lined them with fiber paper to make doubly sure. I then loaded all my bullseye scrap into the resulting 2" wide and 8" long box.
Be sure to support the dams on the outside or you will be sorry - I certainly was! The glass leaked out the corners of the dams and stuck to the sides of the kiln - nothing too horrendous but not what I wanted to happen, as it removed a portion of the brick when I removed the glass. Fortunately I had put the dams on top of a fully kiln washed shelf so the kiln bottom was not damaged.
I then had a sizeable 2" x 1 1/2 inch x 7" high fired glass block - great fluid cranberry pattern though, which I am in the process of cutting into sizeable (read useable) chunks for jewelry ...
