Monica Swanson, of Dunedin, asks :-

Why do some desert people wear dark coloured clothes? Isn't it cooler to wear white?

Cheryl Wilson, of the University of Otago's department of Clothing and Textile Sciences, responded.

Anyone who wears black robes on a hot sunny day knows that that more heat energy is absorbed by black materials than white. Yet some desert dwellers chose to wear black robes in the intense heat of the desert.

Researchers Shkolnik, Taylor, Finch and Borut (1980) have shown that a Bedouin, in the heat of the desert feels as cool and comfortable in a black robe as they do wearing white.

While the surface temperature of black robes is 2-3 times higher than that of white robes, the temperature of the air spaces within the robes remains the same. There are no differences in heat gain, sweating rate, and metabolic heat production by the wearer of the two types of robes.

The wearer of a black robe will be as cool as the wearer of a white robe because cool air from the environment is drawn up through the robe replacing the warm air trapped in the garment with this cooler air. Because there is a bigger temperature difference between the surface of the black robe and the skin there is a greater movement of air up through the loose layers of the black robe than there is through the white robe. So while the surface temperature of the black robe is greater than a white robe, the skin temperature and comfort of the wearer will be similar.