Explosion and Fire Hazards of Polishing Dust

Q: I just heard about a dust explosion in a sugar factory that killed a lot of people. Is there anything similar to worry about in the dusts we jewelers generate?

A: People don’t think of sugar as being flammable. But for the human body, sugar is our gasoline. Its energy storage ability is quite respectable, and we can burn it for energy in our cells because it’s a relatively reactive chemical. This is also why those of us with diabetes have a problem with high blood sugar. It’s very reactive stuff, and normally the body tries to keep levels of sugar floating around to the minimum needed to keep the body fueled. More than that, and the stuff causes serious damage.

With that background in the biochemistry of the stuff, it becomes less a surprise that it’s not quite the same simple chemical it seems. Now, it’s not so easy to ignite as gasoline, and catching fire isn’t usually a problem when it’s in its normally-seen form. But a dry dust? Might as well have a nice mix of acetylene and oxygen floating around.

The stuff in your polishing machine, however, is not in that category. The flammable part is mostly the cotton fluff from the buffs, and that part is indeed potentially flammable. The rest is pretty heavy grease or wax binders, which while potentially flammable, isn’t a dust, but rather caked onto stuff, and harder to ignite. And it’s full of the polishing compounds themselves, which are generally oxides or silicates already, and not flammable. Try lighting a match to an incrustation of the stuff, and you’ll find that while it can burn some, it’s hardly an aggressively flammable material. And since normally it quickly settles out of the air, not forming an airborne dust cloud, the risk is usually minimal, especially since buffing doesn’t generally lead to an ignition source for the stuff.

One related thing to watch out for, however, is grinders and grinding wheels, especially if used with steels or titanium. Sparks flying off the wheel are white-hot, and if they hit a pile of accumulated polishing fluff, that can flare into a fire surprisingly well. Similarly, mounting grinding wheels in your polishing machine and sending hot sparks into the dust collectors is probably not a bright idea. It’s one thing to say the polishing waste is not easily ignited (such as with a static spark), but asking it to not light up when spraying white hot burning steel sparks into it, well, that’s another thing altogether.

by Peter W. Rowe M.F.A., G.G.