Quote Originally Posted by Aggie
brass doesn't need the air cool to harden, it is non ferrous and thus is hardened by work. You anneal the metal to soften it. to harden it when it is non ferrous is to actually hammer bend or other wise mash it. You can also sand blast it to harden it.
Sandblasting, or better - glass bead blasting, treats the surface, so for trying to avoid fractures which start at the surface, it is good. We first learned this by accident racing cars in the fifties when we sandblasted valve springs just to clean them and then they mysterously stopped breaking on the track. Now glass or media blasting is routine.