On Friday, August 31, 2012 10:29:41 AM UTC-10, Stanley Schaefer wrote:
On Aug 29, 4:07*pm, "RogerN" wrote:

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



I did it many moons ago as part of a chemistry course. Natural gas

was the fuel, the torch was more than just a bunsen burner. Pyrex

behaves differently than soda lime, you have to stay with it all the

time or it sags and then freezes, not much time between soft and then

hard. There are several books you can get out there on lab

glassblowing, some are on archive.org. It's one of those things that

it's hard to pick up from a book, you'll have a lot of failures until

you get the skills. For some things, you need a cross-fire torch

array, not exactly a common-place thing. The annealing kiln is a must

for anything but small tubing joints. You can use crossed polarizers

to see the strains in your joints.



Stan

You can make a torch out of 1/2" copper pipe T with an end cap with a hole drilled in it. Make an eye dropper shape out of glass tube and put it through a cork and stick it in the other end of the T. Gas goes through the glass tube pointed at the hole in the copper end cap. O2 or air goes through the bottom of the T and out the hole in the end cap. Adjust gas and air so it burns clean.
Karl