One of my beta readers recently asked about the black tents one of the cultures in The Impossible Contract use in the middle of a Sahara-like desert. The question reminded me about the wholly counterintuitive use of black fabric in extreme heat and how, paradoxically, black fabric is actually superior to white in a handful of small, but incredibly important, ways.
Yes, the color black absorbs more heat than white, and white reflects more heat than black. But according to a study done in 1980, Why Do Bedouins Wear Black Robes in Hot Deserts?, there is a lot more going on than that. One very brave volunteer donned both a full white robe and an equivalent black one and stood for 30 minutes facing the sun at midday in the desert. The temperature ranged from a moderate 95F to a more intense 115F. Talk about dedication!
The results were surprising: according to the article, “the amount of heat gained by a Bedouin exposed to the hot desert is the same whether he wears a black or a white robe. The additional heat absorbed by the black robe was lost before it reached the skin.”
But why is that? Another scientific study done prior to the let’s-make-an-undergrad-stand-for-an-extended-period-of-time-in-the-desert experiment measured how various colors and types of bird plumage released or trapped heat. In 1978, Walsberg, Campbell, & King examined what happened when black or white plumage was fluffed up or flattened down when introduced to heat. To make their study even more interesting, they also varied the wind speed.
What they found was that while fluffed, white plumage let the most heat escape when there was no wind, when there was any sort of modest wind, black fluffed plumage fared much better.
The reason for this somewhat surprising discovery is actually at the beginning of this post: white reflects heat the best. That means from the sun, yes, but also from your own body. So all that heat you’re putting off just gets reflected back at you when you wear white. Black absorbs the heat from both the sun and your body, and as long as the fabric is loose enough for wind to get through, that heat radiates outwards instead of inwards and gets swept away.
Convection only sweetens the deal: in drawing heat away from the body, black fabric encourages more air flow. This works equally well for tents. The black then absorbs any heat from the bodies beneath it while creating a nice, gentle breeze. Ideally.
While you might not notice a difference in most of the United States, maybe next time you take a sojourn through the Sahara or Death Valley, you should try wearing black.