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I think there's some interesting points made in this discussion
by Peter Rowe (rec.crafts.jewelry newsgroup moderator).
refer to:
http://users.lanminds.com/~drewid/jewelry%20techniques%20page.html
(United Artworks) for other interesting articles.
Q: I've used an oxygen/natural gas torch to solder silver and
gold and for brazing. I know that one needs the extra heat of
oxygen/acytelene for welding steel- is it good for platinum as
well?
A: The principal advantage to acetylene setups is their
availability, ease of setup, and portability. Although the
oxy/acetylene flame's maximum temperature is much hotter than
propane or natural gas, the total heat output isn't much higher.
With oxy/acetylene, most of the heat is concentrated at the tip of
the inner cone of the flame, while the outer envelope of the flame
is relatively cool. (It's a great flame for accidentally burning
holes in your gold and silver while trying to get the whole piece
hot enough to melt the solder. )
With natural gas and propane, the heat is much more evenly
distributed throughout the flame, and though the peak temperature
is lower, the overall heating ability of the flame is just as
good. Oxy/acetylene can burn in a much smaller tip than
oxy/natural gas or oxy/propane, making flames smaller than a
pinhead possible if you need them. But acetylene tends to burn
with excess carbon.As well as making the flame much too hot at
the tip, that carbon will not only contaminate some gold alloys
(white golds can form carbide inclusions on melting with
acetylene), but it can be absolutely deadly to platinum.
Now it's somewhat possible to work platinum with oxy/acetylene
if you're always careful to use a sharp oxidizing flame with an
excess of oxygen, although it's still hotter than you need. But if
the flame is at all reducing, or even neutral, that carbon
contaminates the platinum, permanently ruining it. This
contamination makes it brittle as hell. Most quality
platinum-smiths work with either propane, natural gas, or
hydrogen fuels, not acetylene. Sometimes, expecially in repair
work or in working with fine wires, it can be handy. But in
general, oxy/acetylene is better suited to shipyards, muffler
shops, and the blacksmith's studio.
Oxygen and natural gas or propane are much better and cleaner
gasses for working with platinum Hydrogen may actually be the best
gas for this, since it has no carbon at all. It is used in "water"
torches, but the flame is hard to see, and takes some getting
used to. The excess carbon from the acetylene is not all bad- it
can sometimes help provide a deoxidizing atmosphere for working
with silver and gold, especially when burned in acetylene/AIR
torches like those made by Prestolite, Goss, or Smith. These are
quite useful, and work very well as silversmithing torches.
However, few commercial jewelers, working in retail or wholesale
jewelry stores, are likely to be using an air/acetylene torch.
Even with the smallest tips on the Smith, you'd have a difficult
time retipping prongs on a diamond ring, or doing a clean job
repairing a fine chain. Perhaps with practice and enough skill
you could do make it work, but it would be slower than with a tiny
flame on a Little Torch or similar model. But it does make a best
first torch for general hobby metalwork. The Smith air/acetylene
is certainly my torch of choice for most silversmithing. The broad
soft flame makes evenly heating the whole piece much easier, and
avoids much of the uneven expansion and warping that can occur
with larger sheet metal pieces when you try to use a very small
hot flame instead of heating everything gently.
For things like silver constructions, fabrication of whole
pieces of jewelry from sheet and wire, in silver or in gold, or
for similar tasks, the broad soft heat from an air/acetylene
torch is better than the smaller torches usually found on
commercial jewelers benches. But the capabilities of that torch
are much less suited to the commercial jeweler who may often be
repairing existing jewelry, working around stone-set jewelery,
and generally needing to get into and solder tiny isolated details
on an existing piece without messing up what's already there. A
person highly skilled with a Smith air/acetylene torch can
probably get it to do much of this stuff in a pinch. But it's the
difficult way to go.
If you're going to be doing lots of soldered wire work, making
jump rings or chain for example, then the Smith Little Torch is
going to be far superior. Just make sure to feed it with propane
or natural gas if you want to work with platinum at all. For
general gold work, I guess I use my Meco midget most of all. I
much prefer the Meco to the Hoke torch, which is similar. They
both work with natural gas (or propane) and oxygen. I prefer to
hold a torch in my left hand, leaving my dominant right hand to
work with solder, pics, tweezers, etc. The valves on the Hoke are
difficult to work when held in the left hand, whereas the valves
on the Meco- being on top, rather than on the side, of the body-
are equally reachable from either side. Also, the Meco is lighter
and more comfortable, in my opinion. But it may just be that I'm
used to it...
Peter Rowe
Regards, Laurie Veska.
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