The Xtra Wash Factor
How to get more sun protection from a T-shirt
(HealthDayNews) -- You've heard that a plain white T-shirt offers little protection from sunburn. But the Medical Journal of Australia offers this simple advice for improving the protective properties of a T-shirt: Just wash it a few times.
Researchers at Liverpool Hospital in Sydney, Australia, studied the protection offered by a T-shirt that had been washed up to 10 times. With each washing, the sun protection factor (SPF) increased, until it reached a maximum of about 40.
Evidently, as a T-shirt is washed, it shrinks. And as it shrinks, the spaces between the threads become smaller, so they're better at blocking out the sun.
This rule does not apply to pre-shrunk fabrics, or T-shirts that have been worn so often that you can see through them.