I ordered some casting molds and made these:
I thought when I bought these molds that I would be able to make a bunch of these with one process. This is what I have learned:
*The best pieces I made so far of the wine glass mold weigh 0.7 oz. Putting more or less glass in returns less than optimal results.
*The best pieces I made so far of the butterfly mold weigh 1.3 to 1.4 oz. Putting more or less glass in the mold may cause problems.
*Not enough glass results in the hole being incomplete and the glass not reaching all the way into recesses of the mold.
*Too much glass closes over the cone that is supposed to form the hole and could result in breaking the mold.
*Primo Primer works much better than regular kiln separator. I have not tried Boron Nitride spray--it seems expensive and you need to spray it on the molds outdoors while wearing a respirator. And once you use the spray, you cannot go back to using a liquid kiln separator.
*The first couple of pieces I made I used regular kiln separator in the mold. The opaque pieces of glass picked up the kiln separator. All these pieces are also unpleasantly rough on the bottom. I'll have to use my lap grinder to finish them.
*The firing schedule was *very* hard to find. So, here it is:
250 to 1100 hold for 5 minutes
250 to 1360 hold for 20 minutes
350 to 1470 hold for 10 minutes
full to 960 hold for 60 minutes
100 to 700 no hold
*Every piece I made required cold working with at least the grinder and a fire polish. After the first firing, each piece came out of the molds with jaggy edges.
*These molds are meant to be fired with the design face up.
*I used fine clear frit in the first couple of wine glasses I made and there were a lot of bubbles.
*The pieces do not easily pop out of the molds. You have to give the molds a couple of sharp whacks on a hard surface to remove the cast piece.
*These pieces seem to look better with lots of transparent glass.
I think the results are great, but there is definitely a learning curve involved. And I'll have to price these a little higher than what I initially thought due to the extra processes.