Dom wrote:

Fire polishing ???? I did some old bottles years ago with an old
phonograph turntable and a torch ..

Take care ...Tom in Belle Vernon PA- Hide quoted text -



Tom, what sort of flame did you use? I have tried using my oxy-
acetylene, but the glass cracked, and threatened to explode! Will the
type of glass make a difference?

The type of glass makes a significant difference. Common soda glass has
a COE which is significant and you are not likely to be successful
unless the glass is quite thin, like 1mm, or you warm the whole piece
carefully. A common process in production wine glass making is to blow
the piece, score the bowl, then crack off the upper section with a flame
which then fire polishes the rim leaving the finished edge, the thin
section allows this to work. Borosilicate glass has a much lower COE so
the internal stresses built up due to heating are much lower and so
thicker sections can be heated locally without breakage.