A Scientist’s Version of What Not to Wear

January 5, 2016 | Elizabeth Knowles

Colourful knitted wool socks
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Are wool socks really warmer than cotton ones?

If you live anywhere with snow in the winter, you’ve probably had someone tell you to trade in your cotton socks for wool ones. But wool can be expensive and itchy, so it’s worth knowing whether it is really worth the trouble.

Jayde Lovell from Scientific American put cotton and wool to the test in an epic sock battle to determine which are really best to wear in the winter. To get a good idea of how they would fare in different weather, she created two experiments.

In the first experiment, she filled two beakers with water at 111 degrees Fahrenheit (44 degrees Celsius) to simulate a human body. She covered each beaker with a dry sock and left them in a slight breeze produced by a fan. It turned out that the water in the cotton sock’s beaker ended up about one degree cooler than the water in the wool sock’s beaker.

SEE ALSO: How Your Jeans Could Help Clean the Air

Lovell explained that wool clothes keep you warmer because of the nature of their fibers. Wool fibers are scaly and crimped, which creates tiny air pockets that can hold warm air close to your body. Since cotton fabric is smooth, it has no such air pockets so there is less insulation.

In the second experiment, she wet the socks before placing them over the beakers of water. Here the wool was even better as compared to the cotton. The water in the wool sock’s beaker stayed warm at 90 degrees Fahrenheit (32 degrees Celsius), whereas the water in the cotton sock’s beaker dropped to 82 degrees Fahrenheit (28 degrees Celsius).

Cotton fibers are hydrophilic, which means water-loving and is the opposite of hydrophobic. They absorb water, which fills up their air pockets, keeping you wet and cooling you down. Wool absorbs water as well, but its air pockets are still there. It can even absorb up to 30 percent of its weight in water and still keep you warm.

These differences between cotton and wool translate to other garments as well. If you’re going to wear a pair of jeans — which are made of cotton — out into the cold, try a pair of wool long johns underneath. Cotton and wool aren’t the only two options available either. Many types of synthetic fabrics like polar fleece also exist and are engineered with warmth and waterproofing in mind.

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