The relentless attempt by apparel makers to tame human stink. One of the fundamental axioms of playing outside holds that sweat leads to odor. But the culprit isn’t perspiration; it’s the bacteria that feed on it. Smooth surfaces like cotton are friendlier to bacteria than rough ones like wool: its fibers are scaly, with a lot of surface area, preventing bacteria from bonding. (Wool is also hot and itchy, since the fibers are short and hard to weave smooth.)
Endurance athletes, however, spent most of the 20th century pickled in funk, thanks to their predilection for cotton and polyester. Then, in the early 1990s, two outdoor-apparel companies, SmartWool and Icebreaker, started experimenting with wool from merino sheep, which have longer, non-itchy fibers, to create soft, relatively odor-free products. The drawback? Sweaty merino can become heavy, losing shape. So in 1997, a Pennsylvania company called Noble Fiber Technologies developed X-Static, a silver coating applied to nylon fibers that are woven into technical apparel. (The metal’s anti-bacterial qualities have long been known, though recent concerns have emerged about silver’s effects on aquatic environments if it gets into water systems.) Fox River Mills introduced X-Static liner socks in 1998, and X-Static fibers made their way onto the feet of U.S. soldiers and the backs of Olympic athletes. Soon other companies began weaving silver particles into polyester fabrics, starting an anti-stink arms race that continues today. Merino brands blend wool with Lycra to reduce bagginess, while others are looking into materials like zinc, which kills bacteria, and even coffee grounds, which can be incorporated into recycled polyester to absorb odor molecules.