Hydrogen vs natural gas for platinum

Jewelry Discussion
1

I am preparing my shop for platinum casting and repair. I need
as to which fuel to go with. Currently I am using
propane & oxygen, which will not work well with platinum. Can any of
you platinum casters out there tell me which is the better choice,
hydrogen/oxygen or natural gas (with a torch booster)/oxygen. I know
the hydrogen is highly volatile and will need some extra safety
precautions, but which provides more heat, better casting, less
porosity and better torch capabilities?

Complete Jewelry Metalsmithing
Gary L. Mills

2

HI Gary:

I use a hydrogen torch for normal gold/siver casting. Being a
school, we don’t do any platinum.

It’s a great torch, but definitely takes some getting used to. With
a normal torch, you can see the flame to tune the chemistry. Not with
hydrogen. It’s nearly invisible. You end up doing it by ear. Entirely
possible, but it takes some practice to develop the reflexes. I found
it useful to blast some bronze casting grain to start out. You can
see the oxidization state of the bronze very easily, so that makes it
easy to get a sense of how reducing the flame is for a given distance
and ‘sound’. Sheet copper would probably work pretty well too. (The
bronze grain wasn’t a deliberate thing at first, I just had to do
some bronze, and noticed that it made a handy telltale.)

As far as safety’s concerned, we’re not doing anything special with
it. The bottle’s in a locked cabinet in a semi-exterior section of
the shop, right next to the O2. The fire marshall’s been OK with it
for the past 10 years. The good thing about H2 is that it rises and
dissipates very quickly. It’s not going to lurk along the floor of
your shop until it finds the water-heater.

For whatever that all’s worth.
Brian.

3

Gary,

Gary, Why do you think propane/Oxygen will not work? In my
experience

Propane/Oxygen works fine with platinum. Here are the temps for fuel
gas / oxygen combustion temps.

Propane/Oxygen 5,111 F
Hydrogen/Oxygen 5,082 F
Methane(Natural Gas)/Oxygen 5,037 F

Any of them will work. There are those that claim hydrogen is better
but I think this is just personal preference. Unless you really want
an additional fuel cylinder or gas compressor I would stick with
propane.

Jim
James Binnion
James Binnion Metal Arts

4

From what I know, Hydrogen is better for plat. casting because you
need a hotter flame and it will definitely be a hotter flame than
propane or natural gas.

5

I actually prefer propane/oxygen, simply because you can see the
flame. And it’s cheaper, I think.

The big reason I was always told hydrogen might be preferred is that
it eliminates the potential contamination problems that can exist if
the flame has free carbon in it. That can cause problems with
platinum. Normally, simply using an oxidizing flame with the propane
avoids the problem nicely.

Frankly, I’ve never been quite sure what the exact problem with
carbon and platinum is. The proximity of platinum to iron on the
periodic table suggests there might be some similar actual absorbtion
or interaction between the platinum and the carbon, but I tend to be
sceptical of that, what with platinum’s renowned chemically inert
nature.

I did hear one theory once that makes sense, and I tend to believe
it. The idea goes that at platinum melting temps,carbon is an
exceptionally effective reducing agent. enough so that at those
temps, it can reduce even silicon dioxide back to metallic silicon.
Silicon dioxide, or quartz, or silica, is a staple in jewelry from
the fused silica blocks often used to work or melt platinum upon, to
the silicates in fluxes, to the silica just in dust, etc. If there is
silica in contact with the platinum, as well as carbon that can
reduce the silica to silicon, then that silicon will alloy with the
platinum, and THAT produces a very brittle mix. This whole model for
how carbon contaminates platinum nicely explains why it’s so variable
and unpredictable. It needs the combination of both the carbon and a
silica of some sort, before the carbon causes a problem.

cheers
Peter

6

steve - have you found someone in ohio that will set you up for
hydrogen, i inquired about it once and was nearly hauled in under the
patriot act

goo

7

From a previous post:

Selecting the proper fuel to cast platinum is of utmost importance.
Do not use acetylene, since it has a very high carbon content and
expels carbon in the flame. The platinum will absorb the carbon,
leading to contamination and brittle castings.

Although propane, or LPG, is also a carbon-based fuel, it does not
have the high carbon content that acetylene does, and therefore can
be used for platinum casting. Be aware, though, that even when mixed
with oxygen, propane does not burn as hot as hydrogen and thus
requires more time to melt the platinum. This longer melting time can
lead to porosity caused by gas absorption or debris - a direct result
of keeping the metal in the melting crucible too long. If you do use
propane, pay particular attention to the flame: It should be no
larger than 6 inches with a high oxygen setting. A sample regulator
setting would be 5 lbs. of propane with 40 lbs. of oxygen.

The most efficient way to melt platinum is with hydrogen combined
with oxygen. This fuel is carbon-free, and the high heat created by a
proper hydrogen/oxygen mix melts platinum in seconds. But even with
hydrogen, a proper flame is crucial: If it’s too big, the flame will
heat the surrounding crucible, adding to the melt time-and creating
the same problems as those with propane. Use as much oxygen as
necessary to make a relatively small but oxidizing flame. A sample
regulator setting here would be 50 lbs. of hydrogen and 50 lbs. of
oxygen.

All fuel gases are dangerous, and you should have a professional
install your torch systems and fuel tanks. In addition, the regulator
on the fuel tank should have a directional flow restrictor, which
allows gases to leave the tank but not re-enter. For safety, use only
regulators designed for the fuel you’re using.

It’s good practice to install hard pipes near the casting machine,
so you don’t have gas tanks close to the heat of the flame. You can
then attach rubber gas hoses from the hard pipe to the torch. These
hoses should be inspected regularly for leaks and wear. Also, always
turn off your regulator and bleed your hoses after use.

This is especially true if you’re using hydrogen; the molecules are
small enough to seep through even a new hose, causing a fire hazard.
Also, when using propane, remember that it weighs more than air and
can accumulate on the ground if it leaks.

8

Most definitely Hydrogen for Platinum. I have always used this for
plat. and I keep a second torch at the bench just for the "IUM"
metals. A must-must-must is the proper density of protective glasses
when welding or casting with these torches. I know that there is a
big difference in the view when these glasses or shield is used, but
for your EYES SAKE, were them all the time. and put them on before
you even start with the torch. "That’s my story - And I’m sticken
to-it. Stephen Wyrick, CMBJ, CSMP

9

Hi Gary,

I have hydrogen and oxygen. It takes a little getting used to as it
looks and sounds different than what you’re probably used to. You
don’t see the big yellow flame, you see mostly the heat and the
stuff in the air burning and when you combine it with the O2 you get
a roar like a jet engine. We settled on a Smith torch with a single
orifice. We used a rosebud tip on that torch for years but it would
get so super red hot we were afraid it would melt and drop in the
platinum. The single orifice worked great, only problem is that the
flame is so concentrated it can blow the platinum right out of the
crucible so caution is advised. I bought a Degussa Motorcast about 10
years ago specifically for casting platinum (use it for gold too),
what I liked about that unit as apposed to the vertical type
centrifugal casting set up is that all of the spinning molten metal
is contained behind a closed steel door. The platinum is “Gates of
Hell” hot when you let it go and, although it cools quickly, it isn’t
something you want flying around a tightly packed shop. We still use
that Motorcast machine nearly everyday, it’s a nice unit (although
overpriced). Casting platinum is tricky, you need to do it frequently
to develop a touch for it. It’ll sort of freak you out the first few
times you do it, it’s crazy how hot that stuff is.

Mark

10 
Any of them will work. There are those that claim hydrogen is
better but I think this is just personal preference.

We don’t cast platinum, but we’ve had much involvement with it over
the years…

Platinum is well know for adsorbing all kinds of things, notably
carbon. (note adsorb, not absorb). Thus the adoption of hydrogen -
though as Jim says I’m sure sure it makes that much difference.

Our fire marshall has forbidden the use of hydrogen in our building.
It’s extremely dangerous even as gasses go. That’s not that it’s
particulary different day-to-day, just that you may have issues
with the authorities…

Finally, here’s about everything you need to know, or at least where
to look for more:

http://www.ganoksin.com/borisat/directory/library/subject/69/1

11 
I did hear one theory once that makes sense, and I tend to believe
it. The idea goes that at platinum melting temps,carbon is an
exceptionally effective reducing agent. enough so that at those
temps, it can reduce even silicon dioxide back to metallic
silicon. Silicon dioxide, or quartz, or silica, is a staple in
jewelry from the fused silica blocks often used to work or melt
platinum upon, to the silicates in fluxes, to the silica just in
dust, etc. If there is silica in contact with the platinum, as well
as carbon that can reduce the silica to silicon, then that silicon
will alloy with the platinum, and THAT produces a very brittle mix.
This whole model for how carbon contaminates platinum nicely
explains why it's so variable and unpredictable. It needs the
combination of both the carbon and a silica of some sort, before the
carbon causes a problem.

Platinum can indeed combine with carbon to form platinum carbide at
the elevated temperatures of molten platinum. But the theory of the
carbon reducing the silica is also highly likely as a source of
contamination of platinum at high temperatures.

James Binnion
James Binnion Metal Arts

12 
have you found someone in ohio that will set you up for hydrogen, i
inquired about it once and was nearly hauled in under the patriot
act

no, but I can inquire some more if you like. I use natural gas and
farm out my Plat. casting.

13 
From what I know, Hydrogen is better for plat. casting because you
need a hotter flame and it will definitely be a hotter flame than
propane or natural gas.

Another myth, the propane/oxygen flame is hotter than
hydrogen/oxygen. Not a lot only 31 degrees F but it is hotter. The
real difference is that you need almost twice the amount of oxygen to
fully combust propane when compared with hydrogen. So your oxygen
bill will be higher.

James Binnion
James Binnion Metal Arts

14

Dear Mr. Mills:

I am preparing my shop for platinum casting and repair. I need
as to which fuel to go with. Currently I am using
propane & oxygen, which will not work well with platinum. Can any
of you platinum casters out there tell me which is the better
choice, hydrogen/oxygen or natural gas (with a torch
booster)/oxygen. I know the hydrogen is highly volatile and will
need some extra safety precautions, but which provides more heat,
better casting, less porosity and better torch capabilities?

Hydrogen/oxygen is the recommended gas for platinum casting and
repair. A quick check with the metal suppliers like Johnson Matthey
and others will quickly confirm this. You might also talk with Jurgen
J. Maerz at the Platinum Guild who I quote “The most efficient way to
torch-melt platinum is to use hydrogen combined with oxygen.” It
should be noted multicell generated hydrogen/oxygen gas always
provides a perfect mix of two part hydrogen to one part oxygen,
always providing a flame of perfect mix eliminating difficulties
with porosity in platinum or other precious metals.

Hydrogen is cleaner, more uniform, easier and safer to work with. It
should also be mentioned hydrogen/oxygen is much safer than
propane/oxygen. And seldom requires any special precautions.

Hydrogen is lighter and easily dissipates in comparison to propane
which is heavier and tends to pool, increasing the risk of a safety
problem. Our firm (Spirig) specializes in installing flames in
difficult areas, such as industrial facilities, munitions factories,
chemical plants, historic buildings as well as multi-use dwellings
where other systems and torches are not allowed. We do this world
wide. The number of bottled or piped gas incidents could easily fill
a very thick book, and we have often been called in after these
“events” have taken place to replace the original installation. At
the last two MJSA Expo. events, all other torch systems were shut
down at the show by NYC Fire Authorities.

Our system was once again approved (as it is throughout NYC) and was
the only torch system allowed to operate during this event. A large
percentage of our customers, many of them working for the finest
firms in the world, or within their own studios work with platinum
(gold and silver) use our highly recommended fully patented
Spirflames[tm] for all of their bench work. If I can provide you
with additional infromation, please feel free to contact be at
800-499-9933.

Best Regards,
Gary

Gary W. Miller
Sr. Technical Advisor, Spirig
www.spirig.org

15

Since the platinum group elements are highly reactive with scores of
mineral compounds now identified, do you think the ions in these
flames might bond with them?