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[Digest Post] Acetylene & soot

   Acetylene is a very dangerous gas to have around the workshop
if its not totally necessary. You would  be much better using
Propane or Butane and, of these two, Propane is the better as, on
high use torches, it is less likely to freeze up. 

Dear Dave, I totally agree with you regarding Ian’s post.
Acetylene, though highly flammable, is not particularly explosive,
unless subject to pressures above 15psi (actually, 30psi). Propane
(and natural gas, butane, metane, etc) are all highly explosive.
Propane is the most dangerous, because it is heavier than air, and
’puddles’ if there is a leak. That is why it is so dangerous (and
stupid) to use the little 20 lb ‘barbeque’ tanks indoors. They have
pressure release valves which permit small amounts of the propane to
escape to equalize pressure inside the cylinder. Call your local
propane distributor. Ask them about installing ANY propane cylinder
indoors… Even homes which use propane for cooking, hot water
heaters, etc., ALWAYS have the cylinder outdoors, connected by a
line to the interior appliance.

There is a reason why.

Hello Jessica: Open the Oxy valve a bit first and then open the
acetylene and light it up. Michael R. Mathews Sr. Victoria,Texas

Hi Jessica–If you add the oxygen immediately (as little time delay
as possible) after the acetylene, you wont get all that soot. It
takes a little practice, but it works! Sandra

Hi Jessica,

I have a Smith Little Torch Oxy/Acetylene setup, and when I first
*light* the torch I get tons of soot everywhere. I always assumed
this was inevitable but if someone tells me there's a way to avoid
it I'd very happily listen! 

The soot (basically strings of carbon) results from burning
acetylene without sufficent oxy to completely oxidize the gas. The
result is there is a lot of carbon left which forms the soot.

Typically, the instructions for lighting an oxy/acetylene torch are
to open the acetylene valve a little, then light the torch. After
the torch is lighted, adjust the acetylene valve, assuming it was
opened too far. And finally open the oxy valve. Then, finally,
adjust the gases for the desired flame.

There are a couple of ways to minimize or eliminate the soot.

One way is to note the amount the acetylene valve is open when the
soot is at a minimum. Then only open the valve this far when
lighting the torch in the future. With a little practice this bcomes
second nature.

The other way is to open the oxy valve a VERY LITTLE prior to
lighting the torch. This method has some danger in it. Depending on
how far both valves are open, there can be quite a large flame when
the torch is lighted. Also depending on how far the valves are
opened, it may be difficult to light the torch.

The safest option is the first one. Take the time to repeatedly
light & adjust the torch, using the most frequently used tip, until
you get a flame that produces minimum soot. Then practice getting
that setting a high percentage of times the torch is lighted.


Hi Jessica,

I think that original poster might have been me … if so, sorry
for the confusion.

You will always get soot at startup on an Acetylene/OXY setup, but
not on an acetylene/air setup.

The reason is that on an acet/oxy torch, you light the acetylene
first, then add the oxy into the mix. Acetylene burns with a lot of
soot, and will continue to do so until the oxy in the mix is “just
right.” On an acetylene/air system, when you light it, the mix is
already corrected because the mixture occurs (passively) before the
gas ever reaches the torch tip. through the air intake holes at the
base of the tip.

Hope this helps!
Karen Goeller

Hi there, the cleanest way of soldering for me is: Hydrogen and air
or oxygen. I tried city gas and oxy, propane and the worst acetylene,
hydrogen beats them all. The only thing to get used to with hydrogen
is that the flame is hardly visible. I use it with a blow torch (my
air) and with oxygen for Pt and I love it. It is super clean,you get
heat and H2O!! Klaus

Jessica, You can switch to propane it is a much cleaner gas and has
enough heat to do the job. I have three smith torch set systems using

Regards J Morley Coyote Ridge Studio

And once again, thank you all so much! Since Hanuman posted this as
a digest I will respond to you all as one - I’m a bit nervous about
turning the oxy on before lighting; never even knew it was something
I could try - but will indeed try it out. Again, just goes to show
that it’s always best to ask for options rather than living with a
bad situation! Every surface at my bench thanks you :slight_smile:

Jessica in grey grey grey SF