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Little Smith Torch Disposable Tanks


#1

My next comment is for the question about propane and the disposable
tanks for the Little Smith torch. I have the same system, however, I
use MAPP gas because the oxygen lasts a lot longer. (I have
excellent ventilation). If you can smell gas, there is a leak and can
be very dangerous. As I can afford it, I want to replace the
regulators and use standard size tanks. Can I replace one at a time,
i.e., replace the oxygen regulator and tank, but continue to use the
pre-set regulator for propane/MAPP at the same time? (When I replace
the second regulator I plan to switch to acetylene). I purchased my
torch through a website called cyberweld.com Their prices for the
Little Smith and other Smith regulators were the best I found on the
web.

Priscilla Fritsch
LuckyDog Designs, Inc.


#2

To your question about going to refillable O2, yes you may. In fact,
one kit configuration I offer has disposable fuel cylinder plus
refillable O2. Those little disposable O2 cylinders are brutally
expensive, but handy for small spaces, travelling and such like.

On the fuel front, you may certainly also change over to acetylene
instead of LP gases. Here’s the catch. Acetylene is “dirty”,
especially for platinum work, yet you can use smaller torch tips with
acetylene.

Best of, uh, luck to you at LuckyDog Designs

Dan at I.J.S.


#3

Hi Everyone:

Here's the catch. Acetylene is "dirty", especially for platinum
work, yet you can use smaller torch tips with acetylene. 

I’m very sorry, I know this has been brought up before. I am still
not understanding the term “dirty” when applied to acetylene. I spent
my first 8-class semester working with acetylene/air on fine and
sterling with no problems. We practiced on copper, no problem. I
spent my second 8-week semester working with the same on fine silver
and saw others working on 22 karat. I saw no problems. What becomes
dirty?

Thanks
Kim Starbard


#4

It has a high free carbon content. The free carbon reacts with
platinum at welding and melting temperatures and can make it
brittle. This is not a problem with other precious metals as they
don’t react with carbon. It is also dirty in that it is very sooty
when it is burned without proper mixing with air or oxygen as when
lighting it in an oxy acetylene torch. This is not normally seen with
prestolite type torches as long as the tips are not damaged.

Jim

James Binnion
@James_Binnion
James Binnion Metal Arts


#5

Kim, the problems with acetylene are unique to working with
platinum. Air/acetylene is a wonderful fuel to use with silver, and
for many things where the soft reducing flame of that type of torch is
useful, with gold too. oxy/acetylene has the drawback of being a very
hot flame. With larger tip sizes, it simply is much too easy to
rapidly overheat a piece in many cases. but torches with very small
tips, like the little torch or it’s copies, using oxy/acetylene, can
give you very tiny flames that can be quite useful in many
situations.

However, here’s the problem. Acetylene burns, especially when not
supplied with an excess of oxygen, with a somewhat sooty flame.
Normally, with silver and gold, this excess carbon in the flame acts
as a wonderful deoxidizer, part of why these torches are so nice with
silver fabrication. The metal tends to stay nice and clean with an
air acetylene flame. But with an oxygen/acetylene flame, as an
example, turn off the oxygen so it’s just the yellow acetylene
flame, and you’ll see lots of floating little bits of actual carbon in
the air. Burned with a bit of oxygen, those visible carbon floaters
go away, but there will still be unburned carbon in the flame. Until
you’re using an actually oxidizing flame, one that’s sharp and
hissing and VERY hot, there will be this higher level of carbon
available in the flame.

And that carbon is the problem with platinum. At the temperatures
needed to melt platinum, or the higher grades of platinum solder, the
carbon can cause contamination and brittleness in the platinum. The
old conventional wisdom is that the carbon is actually absorbed into
the platinum, much as carbon can be absorbed in iron to make steel
(platinum is quite close to iron in the periodic table, so
similarities can be expected). But with platinum, the carbon does
not form beneficial alternate structures, but rather simply makes it
weak and cracky. I’ve seen an alternative explanation for this that
frankly makes sense to me. That is that at the temperatures involved
with melting platinum, carbon becomes an exceptionally active
reducing agent (this part is of course true), and the explanation
suggests that silicon dioxide, the common silica found all around us,
can be reduced at these temps by carbon, to silicon metal. Metallic
silicon would then alloy with the platinum, and this is what causes
the brittleness. This mechanism would explain why the contamination
problem is sometimes sporadic and unpredictable. Sometimes it
happens, sometimes not. But silicates are all around a goldsmiths
bench. The soldering blocks we usually use for platinum are fused
quartz, or silicon dioxide, for example. Fluxes contain silicates in
various forms. Even house dust contains silica. Thus the need to
simply not allow platinum at melting/soldering temps to come into
contact with carbon, as it risks contamination, whether by the carbon
itself, or from reduced silicon. I don’t know which scenario is the
case, but I and any other platinum smith can tell you the situation is
one to be avoided. It ruins the platinum and makes it cracky and
unworkable.

For the other traditional jewelry metals, air/acetylene is
wonderful, and with small torch tips, oxygen/acetylene can be very
useful. The main drawback to oxygen acetylene is the difficulty of
lighting and extinguishing the torch without going through at least a
short time span with just the yellow sooty acetylene flame spewing
little carbon floaters into the air, and from there, all over
everything…

Note that all hydrocarbon fuel gasses, natural gas and propane, also
contain carbon. So with them when working platinum one also needs to
be sure to use an oxidizing flame for most purposes. But there’s less
carbon, and it’s much less of a problem and risk.

cheers
Peter Rowe


#6

When I was in Jewelry class during casting week we had to have a
special clean up- during the melting phase of the process you could
see a cloud of little black soot particles produced floating around
the area. Metal in crucible was fine, just the area acquired a layer
of sooty bits.

Betsy


#7

Kim

Acetylene burns with a sooty flame when the mixture is fuel rich.
This is sometimes referred to as a carburizing flame. I light the
torch at this setting. When oxygen is added, the light green outer
cone inside the flame disappears. I feel that you get the best flame
for welding or heating metal for bending when there is an almost
equal amount of Acetylene and Oxygen at the tip. While adjusting the
flame, a considerable amount of soot is given off. Even at the
neutral level, there may still be some soot. This gets all over the
place, but much of it is right around the weld. The way to eliminate
the soot is to add more Oxygen. Unfortunately, in my opinion, this
ruins the flame as far as the welding or metalworking I do is
concerned. The heat oxidizes the metal rather than melting it. I
think that the only thing an Oxygen rich flame is good for is cutting
metals which will oxidize easily.

I have not worked with Platinum, but it presents a completely
different problem from Copper or Silver. I understand that Platinum
acts in a way that is similar to Aluminum. By the time you get the
area you are going to weld hot enough, the surrounding metal will
become brittle from the carbon and oxidation at the edge of or in the
cooler area of the flame. There is some debate regarding the
chemistry involved, but I believe that the problem varies with the
impurities present.

Komowkwa