My question is: if I'm not planning on working with platinum
is there really any advantage for me to use Oxy/fuel as opposed to
straight acetylene? I work mostly with silver, sometimes gold. I've
used the Prest-O-Lite torch many years ago and it seemed pretty
good aside from the soot when you spark it up. It's also quite a
bit cheaper than any setup using oxygen.
While the Prest-O-Lite torch is fine for silver and brass, an
oxy/propane torch will be much easier to use when working just on
gold. Unlike silver, you don't have to heat the entire piece to get
the solder to flow on gold. You can, if you wish, still do
acceptable work with a Prest-O-Lite torch on gold. It is not
impossible, just harder to control.
Platinum is different. Platinum and acetylene do not like each
other. The Prest-O-Lite torch will not have a hot enough flame to
weld platinum, and platinum is welded, not soldered. An
oxy/acetylene torch will contaminate your platinum at the
temperatures needed to weld it. That sooty stuff you described will
ruin your metal, and the metal ain't cheap!
White gold doesn't like acetylene that much either. As long as you
work with the yellow alloys, the Prest-O-Lite torch will be fine.
You will also find 18k easier to work with than 14k, since it
doesn't oxidize as readily and looks great with silver.
When you become more comfortable working with gold, you will
probably want to add an oxy/propane (or oxy/natural gas) torch to
your bench. Don't get an oxy/acetylene setup.
In the meantime, you may want to clean the mixer in your torch.
That's probably why you are getting so much soot when you light up.