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Using two torches with different gasses for melting?

Jewelry Discussion
#1

Hello Ganoksin community!

I have a casting class coming up this fall, and I would like to be
as prepared as possible before hand. I have done plenty of casting
in the past and am very familiar with the mechanics of molds, sprues
and melting metal. I teach a basic fabrication class, but until this
season we have always had a different instructor teach casting.
Because of his failing health I have stepped into the role, so I
wish to clear out any remaining questions in MY head prior to
dealing with the questions the students will pose!

My question stems from the issue of melting bronze, and occasionally
larger amounts of silver. We will be doing a number of models and
casting techniques, and I want the students to be able to work in
bronze if they wish, to economize. Inevitably there is one person in
the class that wants to make a heavy project or wax tree, and this
leads to the problem I need to solve.

I have one Oxy-Propane Smith Little Torch with a rosebud tip, which
will be sufficient to melt 3 oz of silver. I also have two
Acetylene-Air torches that we use in the general soldering processes
in class. In the past we have used both A-A torches to melt larger
amounts of silver, but it takes a LOT of gas. In the past we have
had to refill tanks (B tanks) half way through the session when the
use was heavy. However, bronze (Herculoy) is a different animal, and
takes a lot of heat to reach pouring temperature (1975-2100F). I
imagine 3 ounces of that stuff would be very challenging to melt!

I just bought the O-P setup to alleviate some of this issue, but if
someone in class decides to make a heavy belt buckle or cuff
bracelet I want to know the limit of our melting power in advance so
I can provide proper guidance.

My question: If I need extra heat to melt larger amounts of metal,
can I use both Oxy-Propane AND Acetylene-air torches to heat the
crucible, or will the mixing of the flames create an unsafe
condition?

Thanks in advance for any helpful input!
Jean pSmith, Oxnard Gem & Mineral Society

#2

Jean- About two years ago we had to do a largish bronze casting in
our shop. We used both a natural gas and oxy as well as a propane
plumber’s torch to melt. No problems.

Have fun and make lots of jewelry.

Jo Haemer
timothywgreen.com

#3

Hi Jean

You should be able to use both the oxy/propane torch with a rosebud
tip and the acetylene/air torches for casting. When it comes to
melting metal, I find I have to use both torches just to get the
metal hot enough to pour into ingot molds. I have oxy/acetylene,
oxy/propane and multipleacetylene/air torches in my studio, and I
use them all. I find I must use oxy/propane or oxy/acetylene torch
along with my acetylene/air torchwhen I’m melting silver for ingot
pouring. Acetylene/air torches take forever to melt metal and it’s
just not hot enough. Go ahead and use the torches you have in the
studio.

Joy

#4

Interesting! I can melt fairly small amounts of any silver in a well
glazed crucible with a butane torch! I suppose the most I have ever
melted and poured is about 7.5 grams, it doesn’t take long if the
crucible is pre-heated and since I use mostly fine silver (as opposed
to sterling or other alloys) the temperature only has to reach
1751-1763 F (the range has to do with the ambient temperature in the
studio on a given day in a given season!). I use Bernzomatic butane
torches and they reach around 2400 F-3000 F. I like the ST-2200T
model with a removable base. I have used them for many years and keep
them in the student kits for classes, However, I don’t like their
pencil or cylindrical models- in particular their ST200 “3 -in-1
Micro Torch” is problematic, as is their ST500K : of 3, 500K’s all
leaked after just a few uses due to an inappropriate gasket/o-ring
that is exposed to wear with every use and all adjustments while in
use- it just gives out far too fast - on the other hand it is under
15 bucks so as a source of instant fire for camping, in a workshop
dealing with freeing screws and bolts, or stained glass work etc.,
read: infrequent use- OK., it could be a good thing, but its not for
serious studio use for jewelry repair and fabrication).

If you need an Oxy/fuel torch and are exploring the art and craft of
making jewelry the Bernzomatic OX 2550 is a great handy complete
torch kit with a pinpoint flame and will do any melt and pour of any
metal, in any quantity up to about 12 ounces and even cut through
1/4"cold rolled steel- for 50 bucks and the sheer convenience if you
have to take it away from the studio, say, for a craft show or
teaching, it is ideal: athe regulator is pre-set and attaches to the
disposable cylinders of Oxygen and the gas of choice (their
Proprietary MAPP or Acetylene are capable of a bit more than standard
propane) the single-most drawback is the Oxygen consumption of the
torch (at least 2:1) and the environmental impact of disposable
cylinders however you can attach it to a refillable tank but then its
less portable. Nonetheless, for an accessible (practically any
hardware or home store carries them) affordable first Oxy/fuel torch
when you aren’t interested in taking the plunge just yet to a
permanent studio torch solution this is ideal for melting and
pouring, scrap reclamation and just about any other task you would
use a torch for in the shop, studio or around the homestead!! And
having the butane torch for more precision work, like soldering and
repair or filigree work, for less than 75 bucks you can do anything
you can dream up! So, no I don’t work for bernzomatic and have just
used them in addition to the 5 other torch set ups I have (from the
Okai 'hydroflux welder" and a recently acquired Aquaflame water
torch", a trusty Hoke torch that hasn’t failed in 35 years, a
blowpipe set up and an air acetylene torch) the Bernzomatic portable
acetylene/Oxygen torch is versatile- I teach a lot of groups
cuttlefish casting and it is perfectly portable, the disposable tanks
are an issue but for melting silver, gold, alloys, and other large
amounts with a torch instead of an electro-melt furnace, for the
money it can’t be beat…

Oh, apologies for the treatise- this began as a quick comment !!!
…rer

#5

Cool! Glad to hear from some folks experienced. Thanks to you all
for your help!

Jean

#6

Better to use one big torch to melt metal for casting. The longer it
takes, if some metal is molten and the rest takesmore time, the
metal is sucking in gasses. Porosity might be a problem.

#7

Yes I agree. I wish I had one. It’s not in the budget at this time.

Jean