Many years ago when Silver Southwest jewelry was popular I found a
way to get large silver pieces like bracelets hot enough to solder
with smaller torches. I was using an air acetylene torch - I think
it was a Prestolite brand. I went to the local thrift store and
purchased an older type hot plate designed for a coffee pot. It had
an exposed heating wire and a porcelin insulator. I placed the piece
on the hot plate insulators (making sure that the piece didn’t come
in contact with the heater element) and turned it on until the
heater element glowed red. At that point I applied the torch and
completed the soldering.Sometimes the hot plate would work too well
and start to overheat the piece. By turning it off at that point
there was enough residual heat to complete the solder joint. It also
worked well for large, thick flat pieces.
Bob Rush