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Investment cast & torch, too


#1

Hi, Dave. I can field some of this, anyway. If you are just
fiddling around at the moment, you can do some work with a propane
torch (there are hose/handle fixtures available) That’s the
cheapest, but it’s not very hot, the gas is expensive, and it’s
dirty (and smelly). To work silver, not only do you not need
oxy/acetylene, it’s too hot, and promotes oxides in unskilled hands.
The silver/turquoise business in the southwest LIVES on what’s called
"Prestolite". That’s a brand-name handle that fits onto an
acetylene “B” tank, which is 35 cu’, about 18" high. It is
acetylene/air-the handle mixes air and gas, and there’s only one
hose. The handle/hose/regulator is not expensive, and you can rent
tanks if you don’t want to buy. There are only two kinds of wax-hard
wax, and soft wax. There are thousands of variations, but you only
"need" what YOU think you need. Soft waxes are either like putty or
clay, or if you melt them they get watery quickly. As a woodcarver,
I could say outright- use Ferris File-a-wax. (formerly Carvex) You
carve it with files, burs, chisels, just like wood - it is the
industry standard. I prefer blue - green is very hard, some like
purple -
it’s a matter of preference.


#2

Wow! Thanks to Don and John for the helpful torch recommendations!

I have a recommendation too: Get the Rio Grande and Frei & Borel
catalogs. They have tons of torch The Rio Grande is very
helpful with great pictures but Frei & Borel carries a greater
variety of torches.

Here’s my question:

Don said “Acetylene …creates a sooty carbon by-product and can
contaminate metals such as platinum.” I will not be working with
platinum. So will acetylene contaminate silver and gold? If it does
contaminate silver and gold can this be remedied by using a certain
type of flux? I do not want to blow this one drawback out of
proportion if I will not be working with platinum. (I will use the
torch in an area where I am not concerned about the soot dirtying the
work area.)

    • Would a Blow-pipe torch be as effective for small type jobs as
      a Little Torch? (bellows are cool!)

Thanks in advance!
Dan


#3
Acetylene ...creates a sooty carbon by-product and can contaminate
metals such as platinum." I will not be working with platinum. So
will acetylene contaminate silver and gold? 

Hello Dan, Don was right that platinum and carbon don’t mix well and
acetylene does produce a nasty soot that can cause you problems in
extreme cases with platinum work besides just being generally messy.
Fortunately Gold and Silver alloys both contain copper and copper
loves to be treated with carbon. Carbon is used as an oxygen
scavenger to protect copper containing alloys and to reduce copper
oxides back into metallic copper. Now if you crank up the oxygen on
your torch to some blazing hot degree, then all bets are off. I
prefer propane for no other reason than it is not so hot, it is less
sooty (messy), and if my grill runs out of gas, I can grab the tank
that feeds my torch and finish off the meat on the grill.

Best Regards,
J. Tyler Teague
JETT Research


#4

First, #2-Using a blowpipe. Such an adventurous spirit will be
rewarded in time. Never knew anybody who’s actually used one (that
they’ve told me). Have heard they have extraordinary control for
tiny-tiny work, like chains.

Depending on who you talk to, platinum should be worked in the
opposite methods of someone else that you talk to. Don’t use
acetylene because it is dirty, it adsorbs (sic) gases, so use
hydrogen, even though it adsorbs hydrogen, and oxygen, too (that’s
why it’s in a catalytic converter, it strips the oxygen out of carbon
monoxide). Not arguing with anybody, there’s just a lot of
conflicting info out there. However, if someone’s getting sooty
deposits with oxy/acet., they need to TURN UP THE O2, immediately. I
use aceylene entirely, and 80% of my business is platinum - I have no
problems related to gas. Your question, though - It is really just
too hot for silver - I do it, because I have it, but if you are
buying a torch for silver work, it is too much. (though it is
versatile - I also braze and weld). Gold requires a boric
acid/methanol or denatured dip no matter what torch you have, and
after that the question of Which torch? is mostly a question of heat
capacity. Bottom line- I’ve always found, in this business, people
who will say “That’s not supposed to work” (“The Book”). Me, I just
pick up a hammer and go “Thwack!”, and it’s done----


#5
Acetylene ...creates a sooty carbon by-product and can contaminate
metals such as platinum." I will not be working with platinum. So
will acetylene contaminate silver and gold? If it does contaminate
silver and gold can this be remedied by using a certain type of
flux? I do not want to blow this one drawback out of proportion if
I will not be working with platinum. (I will use the torch in an
area where I am not concerned about the soot dirtying the work
area.) 

I believe that the soot only occurs when the acetylene is used in
combination with oxygen. If you are using a PrestoLite type setup,
there will be no soot. If you are primarily going to work with
silver, acetylene / air is the best to use. If you are going to do
gold work, then you should consider something like the Little Torch
which combines oxygen with the gas. I have a blowpipe that I
experimented with and it is difficult to keep blowing. I bought it
because it was in the catalog (kinda like climbing the mountain
because it is there :slight_smile: ) and I was curious.

Marilyn Smith


#6

Acetylene/atmospheric air torches such as Prestolite, Goss and Smith
don’t produce the sooty “floaters” because the acetylene is mixed and
burned w/ oxygen (from the air) as soon as it is lit and doesn’t
have a chance to burn on its own. The flame produced is always a
neutral, well balanced flame where the gas is fully burned without
an excess of oxygen. This is a relatively clean burning flame whose
maximum size-- flame volume-- is governed by the tip used and whose
character-- the shape and nature of the flame, from cigarette
lighter, fuel only, to hot, pin point- hissy- overly oxygenated-- is
preset: The ratios in which oxygen and gas are mixed is factory set
and non alterable. This is fine for general silversmithing.

The trouble is, when you want to step out into the world of jewelry
repair and more innovative smithing and fabrication, such as spot
welding or fusing, spot solder jobs, heat texturing etc. The preset
prestolite simply doesn’t give me the range that I need.

I use a Hoke jeweler’s torch, w/ oxy/propane. The propane is plenty
hot enough when mixed w/ oxygen (I find oxy/acetylene way too hot),
it is clean burning (although acetylene is nice for sooting up ingot
molds) and is available from almost anywhere from gas stations to
Home Depots.

I also cast w/ it-- I have a “Y” splitter on my regulaters and so
run two torches off one tank set. Truth be told, I used to cast 70
dwt (3.5 oz) sterling bracelets w/ the #4 tip on my Hoke. It is a
versatile torch.

Some people prefer the Mecco Midget type or the Smith torch
oxy/propane torch body since they don’t like the knob position of the
Hoke. I’ve used the Hoke for years. I’ve also seen people do
amazingly fine and impossibly delicate work w/ what I would consider
a blunt instrument , the Prestolite-- really, it’s whatever you’re
most comfortable with.

I don’t own the Little torch and have rarely even used the micro
tips available for the Hoke. But I’d still go w/ oxy/ propane for
the Little torch as well (even though you can’t use the two smallest
tips w/ it).

Hope this helps, Andy


#7
  Fortunately Gold and Silver alloys both contain copper and
copper loves to be treated with carbon. 

there ARE, however, exceptions. Too high a carbon content in your
torch flame with some gold alloys, especially with nickel based white
gold, can lead to carbide formation. The result is little hard spots
in your metal that remain as raised bumps when you try to polish the
metal. Acetylene flames can be reducing enough to introduce such
levels of carbon. It’s pretty hard to get a propane or natural gas
flame to both be reducing enough to do this, and also be hot enough
to melt the metal. Also, the situation with acetylene and
platinum deserves clarification. From what I’ve read (most of the
following is gleaned in bits and pieces from various articles in the
platinum guild past publications, as well as from past Santa Fe
symposium publications) Carbon itself actually contaminate the
platinum by itself. But at the melting points for platinum alloys,
carbon becomes an exceptionally active flux/ reducing agent, able, at
those temps, to reduce a common metallic oxide, Silicon dioxide, or
quartz, to it’s metallic form, just as a reducing flame can, at
lower temps, reduce copper oxides back to copper. Silicon metal,
when introduced to platinum, causes embrittlement at very low
concentrations. The thing is that silicates (silicon dioxide, and
other silicon based compounds, are ubiquitous in the metals shop.
All our fluxes contain borosilicates (borax, boric acid),
fluorsilicates, and many of the soldering or melting surfaces we
might use with platinum, such as wesgo crucibles and the like, are
made of fused quartz, silicon dioxide. the result is that it’s
difficult to keep platinum work sufficiently away from sources of
silicon dioxide or silicates, so that a high carbon environment won’t
risk silicon contamination of the platinum. It’s this somewhat
complex mechanism for 'carbon contamination" of platinum that leads
to the way you sometimes have no trouble at all, and other times,
ruin the metal. 46or example, if you’ve a solder joint held up in the
air in clean carbide or tungsten tweezers, the metal is clean, the
solder is clean, and the solder paillon is just balanced on the joint
to be melted, then a bit of carbon in the flame won’t likely hurt
anything. But let a little bit of flux from your tweezers stay on
the paillon, and you can then get a brittle joint…

Peter Rowe