We fuse a lot of bottles at the studio, and no matter how they got set up they would roll, evrything is lever, our ceramice guru and I have checked it twice, we decided it the heat inside the bottles making them roll, it sounded good anyway!
There wher two bottles in there, different colors, company etc thet rolled into each other and wheer still intact until someone dropped them (threw them).
I asked my girlfriend to check her bottles and she said they where still fine, but have been in a box getting ready for the movers and the plate I made got broken on one side when it got knocked, she took it to a pick and paint store and they fir polished it (full fuse) for her and it came back in pieces.
I fired some recycled window glass. A lot of homes in Hawaii have long panes of glass about half an inch thick, I cut them up and put the in the kiln on a fire polish, I set them on a plate mold just to control them and they looked amazing after, the glass was really old and rather nasty looking. Now it looks great, the green tint is gone and is is bright and sparkling. It fused together but I am going to break it up again and re-fire it. I did the same thing a coupe of years ago with float glass and it shattered in the kiln.
Sometimes things work and sometimes they don’t.