I have fooled with a blowpipe a little. Bought it from jewelry
supplier for under $5US, so didn’t see a need to make one. The
blowpipe itself is just a piece of tapered brass tubing with
enough length (12 to 15"?) to keep the flame off your eyebrows
and a right angle turn at the end to allow you to position where
you can see what’s going on. The end of the tubing does have a
sort of thickened nozzle at the end of the tubing, I guess to
protect it from dings and heat damaging the thin metal. You
could rig a nut on the end of a homemade version.
One uses some flame source and blows air to direct and sharpen
and intensify the flame. The most typical flame comes from an
alcohol lamp with a bottle with facets on it which will allow the
wick to be postioned at a 45 degree angle or even horizontally.
If you arrange your soldering block & etc. right you can direct
the flame downwards to the work.
In practice you puff out your cheeks to provide a reservoir of
air and you can get a steady stream if you practice, since when
you close the back of your throat and breath in through your
nose, the cheeks, like a bellows, continue to provide air for the
brief period you are inhaling. Takes some doing, but you can
learn to do it by watching the flame and keeping it steady.
There is a little material on this in Allen Hardy’s book on
Jewelry Repair. Fun to play with, provides a real small flame
for little chain, & etc. if you don’t have a Little Torch or
similar. Heat output somewhat limited. Maybe could get bigger
flame with other flame sources, as older British texts mention
using a “mains gas supply” and a blowpipe hose to the gas-air
torch for general jewelry work. Wouldn’t want to have to cast
that way, tho’!! I think Platinum is out with this technique.
Would be interested in what you are able to do with this.