Does hair color affect propensity to conduct static electricity?

January 19, 2009 10:16 PM

Does hair color affect propensity to conduct static electricity?

I've always heard the old wife's tale that blond hair will get staticy (a highly scientific term, I know) during an electrical storm. As someone with relatively fair hair, I've found this to be true. Weird, non? I was wondering if anyone has any insight into whether or not this is valid or not, and if so why?

posted by faeuboulanger to Science & Nature (8 answers total)

I think the diameter of the hair, the fineness would have more to do with it than the color. Thinner hair would be more sensitive.
posted by lee at 10:31 PM on January 19, 2009

Darker hair has more pigment (obviously), and pigment has weight. Very dark hair will be heavier and thus less likely to visibly frizz up. I don't think it conducts any less electricity, but the effects are less obvious. If you try one of those Van de Graaf generator experiments, you can see the difference pretty clearly.
posted by nasreddin at 11:32 PM on January 19, 2009

Yeah, the point is about hair texture, not hair color. Blond hair tends to be thinner and finer than dark hair (though this certainly isn't a hard-and-fast rule), and is thus more prone to show the effects of static.
posted by scody at 12:03 AM on January 20, 2009

Thinner and drier = more static. Heavier or less-dry = less static.
posted by rokusan at 3:54 AM on January 20, 2009

Slighty off-topic, but hair doesn't "conduct" static electricity. IANAPhysicist, but I think this explanation is correct (Danger, science ahoy!):

Electricity is all about the flow of charged particles. In solid objects we have negatively charged electrons which can sometimes move around, and positively charged ions (atomic nuclei with too few electrons attached) which can't move around.* Most of the time these are in balance, so there's no net charge.

When you have a buildup of excess free electrons at one end of a conductor (say, a piece of wire), they flow along that wire away from the charged area. Soon the whole wire quickly has the same net charge. Crucially, if the wire is touching your body (your moist skin conducts electricity very well) or any other conductor, the charge flows through the wire, over your skin and away; so the wire (or any conductor) never builds up an excess of electrons. As long as it can keep conducting electrons away from the source and offloading them into something it's touching, the wire keeps a neutral charge.

Static electricity happens when this is prevented. Hair is not a conductor -- it won't allow electrons to flow through it -- and neither is the oil that coats hair. So when electrons are removed from or added to your hair (creating a net charge), electrons can't flow away from or to that site to balance out the charge. This is static electricty, "static" meaning that it isn't able to flow away. Hair stands up beacuse all the similarly charged sites are repelling each other. The crackling noise is made by arcs of electricity, tiny lightning bolts made as groups of electrons jump across the air to or from nearby objects, to balance out the charge.

Er, so my over-explained point was that hair doesn't conduct [static] electricity; if it could (like metal does) you wouldn't see the affect. It's more correct to say that hair allows static electricity to build up.

And to actually answer your question: Hair colour is controlled by the exact types of protein your hair is constructed from. They're all very similar in structure despite their colour, so I'd be very surprised if the colour had any effect on the build-up of static electricity.

I'll nth everyone else who said it's controlled by how fine your hair is, with fine hair being lifted more easily than thick hair. It could also be something to do with your shampoo - maybe blondes tend to use a different type of shampoo which affects the conductivity or its ability to build up charge?


*In liquids and gases it gets more complicated: big molecules often have a slight net charge, so instead of just negative electrons moving one direction, you get variously sized and charged molecules heading in both directions. The principle is the same though: a net flow of charge to cancel out an inequality somewhere in the system.
posted by metaBugs at 7:27 AM on January 20, 2009 [2 favorites]

The putative greater fineness of fair hair is a plausible enough explanation, but the melanin which distinguishes darker hair from fair does have surprising conductive properties:

Melanins, in the synthetic sense, are "rigid-backbone" conductive polymers composed of polyacetylene, polypyrrole, and polyaniline "Blacks" and their mixed copolymers. The simplest melanin is polyacetylene, and some fungal melanins are pure polyacetylene.

In 1963, DE Weiss and coworkers reported[21] high electrical conductivity in a melanin, iodine-doped and oxidized polypyrrole "Black". They achieved the quite high conductivity of 1 Ohm/cm. A decade later, John McGinness, and coworkers reported a high conductivity "ON" state in a voltage-controlled solid-state threshold switch made with DOPA melanin [4]. Further, this material emitted a flash of light—electroluminescence—when it switched. Melanin also shows negative resistance, a classic property of electronically-active conductive polymers. Likewise, melanin is the best sound-absorbing material known[22] due to strong electron-phonon coupling. This may be related to melanin's presence in the inner ear.

I think it's entirely possible dark hair will not hold a static charge as well as fair hair does because of the conductivity of melanin.
posted by jamjam at 9:27 AM on January 20, 2009 [1 favorite]

Another factor to consider is that chemically colored hair is usually drier and thus more prone to static electricity buildup than non-treated hair. I have no data to back me up on this next part, but it has always seemed to me that more people (especially women) die their hair lighter/blonder than darker. So the people who get worse hair-static due to color treatment might add a disproportionate number of blondes to the general pool of static-y people.
posted by vytae at 11:16 AM on January 20, 2009

Another effect, possibly contributing to hair fineness vs. static-y-ness, comes from electrostatics: the charge density on a conductor goes up as the curvature gets tighter. This is one reason why tall pointy things work as lightning rods, and why you get carpet shocks off your fingertips more often than off your palms. (Some dry day when you're getting lots of carpet shocks, compare how easily you can make one from your fingertip to the corner of a doorknob vs. from the flat of your hand to a flat piece of metal.) If you compare two hairs with the same charge per unit length, the finer one will have a stronger electric field at the surface.

Also, straight hair tends to be more cylindrical, while curlier hair tends to have a ribbon-shaped cross section:

 __________
(__________)

(The hair comes out of the screen and curls up or down.) On this shape, charge would tend to move from the flat surfaces of the ribbon to the tightly curved edges. So between two hairs with similar weight, but one straight and one curly, the curlier hair would develop stronger local electric fields for the same charge and frizz up faster. This squares with my anecdotal experience.

This problem would be fun to try and treat quantitatively.
posted by fantabulous timewaster at 1:22 PM on January 22, 2009