Thanks for the info Jesse. Your reply confirms what I was told a
while back about hydrogen having a much cleaner and hotter flame
than propane thus reducing the need for high levels of oxygen under
typical propane/oxygen melt conditions. I am a little familiar with
the type of forming gas (or argon) which you speak of for
eliminating oxygen above internal crucibles on high priced casting
units such as the nuetec or memco etc.
However, Im looking to melt with hydrogen/oxygen thereby replacing
my propane/oxygen setup. I was told by an old timer he used a
formula which he also termed forming gas that was (and this was
expressed to me a tad unclearly) 75% hydrogen and 25% nitrogen for
melting in place of propane. (?) Although I cast great with my
present propane/oxygen tanks, Im always striving to improve when
improvement is possible. Even if it cost a little more.
Hydrogen seems like the ideal gas to cast with. Other than the
safety concerns, it doesn’t smell, low radiation, it is not only
cleaner than propane, but hotter, which seems to be a great benefit
(porosity) if I need less oxygen to melt my metal; and yet I wonder
why more casters aren’t using hydrogen? Sure gonna do my homework on
the safety concerns. Is it the safety concerns that many don’t use
it? Just wanna make sure before I strike my match 
Thanks again for your insight Jesse and to the many other Ochidians
for the important feedback on hydrogen.
Steve in Hawaii
So now I use hydrogen/oxygen. No nitrogen mixed in though. I
really like it. It's very hot and clean. The flame is hard to see
at first but I got used to it.
Many Thanks Annette, Pure hydrogen for melting. Are there any safety
concerns and or rituals you do which I should make important note of
when I switch to pure hydrogen?
Steve in Hawaii
Steve, No, I’m sorry to say I don’t have any safety tips for you.
I’m pretty sure the folks at the welding supply sent me with a
safety data sheet so I think where ever you go to get the hydrogen
is the place for you to get safety info. I do know that it
dissipates upward which is a good thing. If there would be a gas
leak it would not pool on the floor but would dissipate upward and
work it’s way up and out of your studio unlike acetylene which drops
and pools on the floor i think. Also it’s very important not to have
oils on or in the hoses or connections and I’m sure you are aware of
checking your valves and all with a soap solution. Have you talked
to any experts? I am no expert on any of this, just a satisfied
hydrogen/oxygen user. Annette
Since the hydrogen/oxygen flame is so hard to see, especially
wearing dark glasses, has anyone heard of a light source to
illuminate the work right at the torch. Although you still couldn’t
see the flame, you could see the work better. I use flux in my
oxy/acet. torch system in the acetylene line and it burns with a
green flame. This actually helps light up the work area and makes
the flame visible. What about a laser pointer attached to the
torch?
Tom Kruskal
The 75% Hydrogen-- 25% Nitrogen is dissociated ammonia. I don’t
remember ever blending this ( this doesn’t mean it wasn’t ever done)
i worked in the industry from 57 into the 90’s And at one time
or other was involved with a lot of hydrogen and was responsible for
a lot of the filling facilities. In the earlier days i seem to
remember that we filled a little about 7 % H2 in New England.
Larger customers use bulk supplies and we often would replace actual
dissociated ammonia with a Blended system but it was always about
10% max. Some of the annealing used brazing furnaces for stainless
steel used pure hydrogen. for normal atmosphere protection the 5%
is fine.
Jesse
Hi Steve, This is in reply to your question as to why more jewelers
don’t use Hydrogen. I have been using Hydogen/Oxygen for platinum
casting for about a year. But I still use propane/oxygen for casting
gold. I found the hydrogen to be too hot for melting gold, I
overheated it a couple of times. It is hard to judge the amount of
heat you are creating because it is hard to see the flame, this
isn’t an issue with platinum. I am sure I could have adjusted to it
but it was just as easy to add a tank of hydrogen and have both
torches hooked up to the oxygen tank while each has a different fuel
source. One concern with Hydrogen is that it can self ignite if you
open the tank valve without a regulator on it. Apparently just the
friction of the dust particles in the air are enough to ignite it.
So we use it with a healthy dose of respect. Mark