Re: How does aluminum foil stop static electricity in

> I can't remember where, but I was advised to use a ball of aluminum
> foil instead of dryer sheets to stop static in the dryer.

Amazing! I've never heard of this effect before. I'll have to try it and see how well it works. I can't give you a simple answer, but I do see some possibilities.

1. Sharp points on the foil will create corona discharge, making the air slightly conductive and discharging the clothes.

But you mention that the foil works just as well when pounded into a smooth ball? Then it probably isn't the sharp points doing it. (Hmmm, I wonder if a hollow aluminum ball would work just as well.)

2. Extremely fine aluminum powder coats the clothes, making them slightly conductive and discharging the "static." As the wad of aluminum strikes and rubs the inside of the dryer, it will make streaks of aluminum. (The same thing happens when you drag aluminum across paper or across pottery.) The clothing then rubs this aluminum off the dryer and spreads it around as huge numbers of incredibly small metal dust motes.

But for this to work, I think the particles would have to touch each other. If the clothing is covered with aluminum dust motes, the charge won't jump from particle to particle. In other words, a powder is not a conductor unless the particles are touching together.

3. As in #2, extremely fine aluminum powder gets into the dryer as the wad of aluminum scrapes across the painted interior. But rather than making the clothing into a weak conductor, the powder coats the clothing, perhaps oxidizing into aluminum oxide first. Then, when powder-coated fabrics touch together, we have powder touching powder rather than different fabric fibers making direct contact. The powder grains hold things apart at the microscopic level and keep the clothing from touching each other. Without contact between differing substances, no charge-separation occurs.

I think #3 is probably the best bet. You'd need lots of particles, but they could be really really small. "Dryer sheets" work in a similar manner: coating the clothing with an extremely thin oil layer, so when fabric fibers collide, you have oil touching oil, and no fabrics actually touch together.

One other thing to try: stop using the aluminum foil, and see whether your clothes still have static cling. Maybe the anti- static effect is coming from a buildup of oil from back when you were using "dryer sheets." If you use the dryer sheets for a few months, then you stop using them, does the anti-static effect go away after the next load? Maybe it persists for months and months. (If so, then the dryer-sheet manufacturers are selling far more sheets than we need!)

William Beaty
Electrical Engineer
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