Of the 2 pieces we had that were stuck in the molds – one was overcooked. Whatever the cooling temp was set at, it was too low, as the kiln fired for… (now I’ve forgotten) somewhere around 12 or 24 hours just for the cooldown. That made the glass stick. I’m assuming that the jewelry pieces that were stuck in a mold just didn’t get enough kiln wash. Or, the person firing them didn’t realize that kiln wash was a necessity.
When I heated these to release the glass, I heated to slumping temp – 1250F. The bottle was still not flexible when it released, as the bottle cracked when it hit the kiln shelf. Also, since that one had wrapped a bit around the edge of the mold, I had on taller stilts. Probably the 1" one we’ve got back there. Shorter stilts probably would’ve been okay. I had the jewelry rounds on shorter stilts, and they didn’t break. I can tell that the piece fell before it hit slumping temps, because the pieces changed shape after falling.