Neither a propane torch nor a MAPP torch is likely to be effective
setting off the Cadweld powder no matter how hot you get it. Cadweld
powder burns with an oxidation reaction, and the atmosphere in the
vicinity of a propane/MAPP flame is primarily a reduction environment
due to incompletely burned gas. It's the same reason that the inside of
a torch flame will remove the oxidation from a piece of copper sheet or
plumbing fitting. This topic comes up here from time to time, and
almost nobody is successful using a propane torch with Cadweld powder.
Match heads are a different story, though, and I've used them myself in
a pinch. They aren't completely reliable, but I don't see how they are
any less safe than the normal starting material.
I don't use One-Shots since I made my own regular mold from a graphite
plate and use standard powder that I bought on eBay. I always saved a
bit of the starting powder from every shot I made so that I could have
some extra available if one of the shots was particularly balky.
By the way, I also played around with making my own Cadweld powder from
scratch. The reaction is a pretty simple one involving only copper
oxide and aluminum powder*, but I learned that the particle size of the
ingredients is critical for having a controlled reaction. Coarse
particles are very difficult to fire off, while the fine stuff
(laboratory grade) I was able to buy goes up like the flash powder
photographers used to use. If you compare the Cadweld starting material
with the normal powder, that's pretty much what you see ... the starting
material is simply finer grain. I suppose if you were willing to risk
losing an eye or having your hand blown off you could try grinding the
regular powder into finer particles, but I would strongly recommend
against it.
The best advice I've seen here so far is from the guy who recommended
you just throw it away and use a new one.
73,
Dave AB7E
* 3CuO + 2AL=Al2O3 + 3Cu + HEAT (lots of it) + LIGHT (lots of it)
On 1/21/2013 2:53 PM, K8RI wrote:
On 1/21/2013 4:23 PM, SPWoo wrote:
Hi All,
I'm having a problem where one of the cadweld one-shot doesn't have
any of the igniting powder in it. From what I've gathered the main
powder material needs a very high temperature to ignite. So far I've
tried a torch (MAPP gas) but still the main powder fails to ignite
despite the powder was glowing red. Someone has suggested using a
magnesium fire starter. I didn't have any problems lighting the
other cadwelds with a flint but what does one do if there's no
igniting powder? Your help is greatly appreciated. 73.
Just a propane torch should ignite them. I've ignited them with match
heads from the old kitchen matches, which isn't very safe and I do not
recommend.
If it was glowing, it should have ignited.
We're missing something.
73
Roger (K8RI)
Best Regards,
Jonathan Woo, W6GX
(970) 646-1711
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