HOW COME? Blame copper, not chlorine, for green hair

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How come when you go into a chlorinated pool your hair sometimes turns green? asks Sara Guarascio, a student at Long Island Lutheran Middle and High School in Brookville, NY.

Ah, summer. Jumping into a pool of shimmery blue water on a hot afternoon. The sounds of happy splashing, the smell of coconut sunscreen, the beachy green hair . . .

A sickly green tint after too many dips in the pool is most obvious in blonde hair. But red, brown, or black hair can take on a green tinge, too. The darker the hair, the harder it is to detect. Still, you may notice the green in a bathroom mirror lit by fluorescent lamps, which emit a greenish-white light.

But don't blame the chlorine; it's actually copper that's the culprit. Ever notice how a bright penny or a gleaming copper water pipe can turn green over time? Just as iron corrodes when exposed to the elements (leave an iron frying pan in water, and a sprinkling of red rust will form), copper also reacts with oxygen, water and other chemicals. The result: a green layer of oxidized copper ("verdigris") on the surface of a pipe or penny.

Something similar happens to hair exposed to copper. How does copper get into a swimming pool? Just as chlorine is added to kill bacteria, copper-containing algicides may be used to keep pools from growing algae. More copper may seep in from old plumbing fittings.

Hair is made of a protein called keratin. The covering of each strand -- the cuticle -- is like shingled tree bark. When the shingles lie flat, hair looks shiny and feels smooth. But harsh sunlight, blow-drying, flat-ironing, and chemical processing can damage the cuticle. Like a shingled roof after a windstorm, the once-smooth cuticle is ruffled. And pool chlorine only adds to the damage.

Copper ions in water are positively charged, and are attracted to negative charges on the hair shaft. When the protective cuticle is damaged, hair is especially vulnerable. Over time, a faint green patina of oxidized copper builds up on hair.

A swim cap can protect hair from both chlorine and copper. But if wearing a cap isn't appealing, try coating hair with a leave-in conditioner or a bit of coconut or olive oil before swimming. Oils make it tougher for copper to glom on to hair. And be sure to rinse hair with plain water after getting out for the day.

Hair already green? There are shampoos formulated to remove that metallic tint. But home versions may be just as effective. For example, try using vinegar or lemon juice in water, since an acidic rinse can also get rid of the annoying green.

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