I tried this with my kid. For a year I let him figure out every explosive he could with *my* supervision. He GOT THE MESSAGE that safety was first! When one of his concoctions blew a three foot crater in our driveway I called a halt to the whole thing.
Believe it or not, it worked. He got it out of his system and moved on to other things.
One thing I learned was that even if your own kid is being safe when he is alone or with you, you still have to worry about other kids from the neighborhood playing with fire when they are visiting your house.