"RogerN" wrote in message
...

Messing around with chemistry and such, would sometimes be nice to
be able to fabricate with the glass tubes. I can bend them easy
enough with just the alcohol lamp, propane torch does even better.

I can make a poor man's condenser using a small diameter tubing for
the vapor and a larger tube for the water cooling jacket, rubber
stoppers at each end of the larger jacket tube, 2 holes in each
stopper, one hole for the vapor tube that passes through and another
tube on each end for cooling water inlet and outlet.

This could be done neater if I could weld glass nipples onto the
cooling jacket, and neck down each end of the cooling jacket and
weld to the tube that runs inside. I've been playing with the glass
with a propane plumbing torch, seems difficult to work. When trying
to weld, too large of an area of glass gets too soft, I think I need
a flame that is more concentrated, heating to melting temp right at
the joint but not so much to the surrounding glass.

Anyone here tried working with borosilicate glass with metalworking
welding torches? I don't see why it wouldn't do what I want
(joining glass) but I don't have the tanks anymore. I don't mind
getting the tanks, but I would like for it to work before I lease
tanks and buy oxygen & acetylene (or propane). When I had tanks, I
had them for several years and hadn't used half of my gasses up yet,
that's why I took them back, I was paying monthly rental on
something I hardly ever used.

RogerN

Here are three results from Gutenberg:
http://www.gutenberg.org/ebooks/sear...+glass-blowing

IIRC in chemistry class we used natural gas to practice on soda-lime
glass. I never tried borosilicate, but I made miniature glass animals
in the dorm room with a candle flame and blowpipe, using the readily
available fragments of broken bottles, light bulbs and globes etc. The
milk glass globes in the bathroom turned mottled brown like the back
of a fawn if overheated with excess air.

It does take a lot of practice to get the hang of how hot glass
behaves, and wouldn't hurt to have someone show you the tricks which
are hard to describe in print.

Be SURE to anneal the piece so it doesn't shatter from locked-in
thermal stresses.

Don't apologize for the rubber-stopper condenser, it avoids the
problem of differential thermal expansion.

jsw