Wool is a naturally insulating fiber that has great wicking qualities to pull moisture away from the skin. Wool fibers are "bouncy" and provide resilient padding for your feet. And because wool is a tough, long-lasting fiber, your socks will be cozy for many years.
Whether you buy mass-manufactured wool socks or are lucky enough to get a pair of hand-knitted wool socks, the key to caring for them is understanding which type of wool yarn is used. This will determine whether the socks can be machine washed and dried or need to be hand washed.
Superwash Wool vs. Virgin Wool
Wool yarns come from the fleece of sheep; cashmere and mohair are derived from goats. The hair is spun into yarns, and if left untreated these are called virgin yarns. Each hair is made up of scales. When the hairs are exposed to high heat either during washing or drying, the scales bind together. This binding is what causes shrinkage, which is often permanent.
Superwash wool yarns have been treated to be shrink resistant. The wool fibers are exposed to a mild chlorine solution for a very short time, followed by rinsing, application of a polymer resin, and drying. The chlorine exposure removes the protective outer layer from the wool fibers and smooths the scales. The polymer resin further smooths the fibers and significantly reduces the chance for shrinkage caused by the interlocking of the wool’s scales.
Wool receives the superwash label if it can be machine washed in warm water and tumbled dry on a low setting. However, it is important to note that all wool fibers are technically washable and are often labeled as such. But washable wool isn't the same thing as superwash. Superwash is a patented process that assures the fabric can be machine washed and dried without damage if you follow the label instructions.
Care for Superwash Wool
If your socks are made of treated superwash wool yarns, they generally can be machine washed using warm water and regular laundry detergent and then tumble dried on low heat. Do not use a hot water wash cycle or high heat in the dryer; this can damage the protective resin coating. And once the protective coating is damaged, the fibers can and will interlock and cause shrinkage.
Care for Virgin Wool
Hand washing is the best choice for socks made from virgin wool. Hand wash them like you would other delicate clothing, but use a commercial or homemade wool wash soap. After rinsing well, the socks should be air dried flat away from direct heat sources to help them retain their shape. If you choose to machine wash virgin wool socks, use the gentle cycle, cold water, and wool wash soap. Use the slowest spin cycle possible. And allow the socks to air dry; never put them in a hot automatic dryer.
More Care Tips for Wool Socks
Never use chlorine bleach on wool socks. In excessive levels, chlorine bleach will stiffen and weaken the fibers. If there is staining or yellowing of wool socks that needs to be treated, use an oxygen-based bleach as a presoak. Mix a solution of oxygen-based bleach (such as OxiClean, Clorox 2, Country Save Bleach, or Purex 2 Color Safe Bleach) and cool water. Follow the package directions for how much product per gallon of water. Completely submerge the socks, and allow them to soak for no more than one hour. Then, rinse well.
While wool has natural antibacterial qualities, you might wish to add a disinfecting step while washing your wool socks. This can be done by using a pine oil disinfectant, which is effective in warm water. Brands include Pine-Sol and Lysol Pine Action. It should be added at the beginning of the wash cycle. You also can use a phenolic disinfectant added to a warm wash or rinse cycle. A popular brand is Lysol Laundry Sanitizer.