Etiquette says you stop wearing white after Labor Day. Black cotton absorbs 61% of the sunlight hitting it. How much does white cotton absorb?

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White cotton absorbs 17% of the sunlight that hits it; black cotton absorbs 61%. Color matters more than fabric here, because a polyester-cotton blend measures the same 61% in black and the same 17% in white. The old rule against wearing white after Labor Day had physics behind the etiquette: white was summer clothing because it threw the heat back.

Summer white was never only fashion. White cotton absorbs 17% of the sunlight that hits it; black cotton absorbs 61%.

Source: Japanese Journal of Biometeorology (Watanabe et al., 45:4) · checked 2008