DANGERS OF AN "EMPTY" MILL JAR

This accident occurred when dropping steel milling media into an aluminum jar that I used for milling magnesium chips to powder. Although the jar was "empty," the trace remains of the magnesium powder from the previous batch ignited from the impact of the fourth ball, resulting in a very brief but intensely bright and hot flareup that scorched my hand severely.

The aluminum mill jar with four steel balls. There was only a light dusting of magnesium powder on the walls of the jar. As you can see, it is quite pitted now. The white residue is magnesium oxide from the fire.

My hand. Because I was dropping the balls into the jar one by one, the lower edge of the hand and wrist were the most exposed to the flare-up. Fortunately, no tendons were damaged and this burn, though quite painful, should heal fairly well.

Three weeks later. Christmas Day, in fact. My most gratefully received present -- an almost completely healed hand. Rather thoughtfully, Santa brought me a pair of full-length Nomex gloves and a full face shield.