Science Wednesday: All the Cool Nomads are Wearing Black

by Katie Bowell, Curator of Cultural Interpretation

During our latest heat wave, I decided to watch documentaries about places much hotter than Colorado, in the hopes of feeling better about my own temperature predicament. One film, Shifting Sands: The Story of Bedouin Women at the Crossroads, was fascinating, but left me with a nagging question in the back of my mind. Why do cultures like the Bedouin and Tuareg, peoples who live in the extreme heat of the desert, wear black robes? I’d always been told to wear light colors when it’s hot since dark colors absorb more heat, and robes are what I wear when I’m cold, not what I’d imagine putting on in the middle of the desert.

Tuareg Woman

I did a little research and, as it always does, physics provided me with an answer. It turns out that when deciding whether or not clothing will keep you cool, you need to consider absorption and convection.

It’s true that dark-colored clothing absorbs heat and light-colored clothing reflects it. But, light-colored clothing won’t always make you feel cooler. You see, while light-colored clothing reflects external (coming onto your body) heat away from your body, it also reflects internal (coming off of your body) heat back onto your body. Dark-colored clothing absorbs external heat, but it also absorbs internal heat, wicking away the heat that your own body is emitting. Combine that information with the fact that even a slight breeze blowing over dark-colored clothing will convect the heat away from the cloth faster than it’s being absorbed, and sometimes you can be cooler wearing dark colors than you are wearing light colors.

So, black robes can be cooler than white robes, but it still seems like it would be hot wearing a robe. Well, it turns out it’s all in how you wear it. Unlike the way I bundle myself up in my flannel robe, Bedouin robes are loose. Loose robes means that air can circulate within them. Since warm air rises and is replaced by cooler air, wearing a loose robe means that the movement of warm air out of your robe brings cooler air in, similar to how a chimney works.

So the next time you know you’re going to be out in the heat, try wearing loose, dark clothing. Not only will you look cool, you might feel cool, too.

July 2010

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