RJ wrote:
During the 70's hobbyists were cutting bottles
to make glasses, vases, bowls, etc...

Tie heavy twine around the cut line.
Soak in lighter fluid, light, let burn,
then plunge into a bucket of cold water.

The bottle should part right at the string line.
Then use a Dremel tool to smooth the cut.

You've got lots of bottles...experiment !

I seem to recall that one could use nichrome wire
to do that, with better results. (Cleaner edge,
less cleanup.)
The wire is wrapped tightly around the bottle to
be cut. An isolation transformer drives
your Variac which powers the nichrome.
The wire creates a very localized strip of hot
glass. Dipping the bottle in water causes a
clean fracture at the heat line.

Grind the lip of the glass for a flat surface
and rounded corners.

Use all safety measures, like eye protection and
gloves!


--Winston