John K Jordan
>>>if you want to experiment, just lay half a pad of 0000 on something fireproof and send some of those sparks into it and watch what happens.
For even more excitement saturate the steel wood first with very fine aluminum powder. This is thermite, gets hot enough to weld. It makes a great science demonstration.
The worst spark throwing I know of is cutting thick steel with abrasive wheels on a chop saw. The particles are so hot and stay hot long enough to bond to other steel particles accumulating on the spark guard a foot from the cutting point. The can build up a strong steel mass: