Stand-back and don't get any on you.

http://www.youtube.com/watch?v=WrCWLpRc1yM

http://en.wikipedia.org/wiki/Cadwelding

GA. Add to that, "Don't breathe the fumes."

<..."Don't breathe the fumes."...>

Quite, though one really wouldn't want to stand that near anyway while it's "going off"....

Ah, but thermite makes such a nice incendiary grenade though.....=b

(been reading "Lucifer's Hammer" again...)

Ronron,

To summarize from the other posts--

• It is a method of welding in which the energy to create the weld is supplied by the ingredients, instead of an outside energy source such as a flame or generator.
• Once the reaction has been started, stopping it is virtually impossible until all the components have reacted.
• It can put out very large amounts of heat quickly, so sparks, flying globs, fumes, intense light, and similar are normal.
• In abnormal conditions the mold within which the welding reaction is done can melt or shatter, so anything nearby can be damaged or burnt. Very hot parts can fly a considerable distance.

This list is not complete, but I hope it gives you guidance for the more important question of what safety precautions you need to take before doing exothermic welding.

--JMM

exothermic welding is also used to make grounding connections. It is irreversible and makes a very low impedance splice. Cadweld is a brand name