Wool has long been the traditional favorite of outdoorsmen – it’s warm when wet and durable for its weight. Wool is a natural fiber composed primarily of keratin, a protein found also in hair, fingernails and animal hooves. Sheep serve as the primary source of wool for clothing. Wool has several qualities that distinguish it from hair or fur: it is crimped, it has a different texture or handle, it is elastic, and it grows in staples (clusters).
Wool’s scaling and crimp make it easier to spin fleece by helping the individual fibers attach to each other, so that they stay together. Because of the crimp, wool fabrics have a greater bulk than other textiles, and retain air, which causes the product to retain heat or to keep the heat out.
The quality of wool is determined by the fiber diameter, crimp, yield, color, and staple strength. Fiber diameter is the single most important wool characteristic determining quality and price. Merino wool is typically 3-5 inches in length and is very fine (between 12-24 microns)
Wool is hydrophobic working to move moisture (aka: perspiration) from your skin to the core of the wool fiber on to the outside environment, where it can be transferred to the atmosphere.
Wool doesn’t catch on fire like some synthetic fabrics. Have you ever been around a campfire and had errant spark fly out and hit your synthetic fleece or nylon outer shell?
What is Merino Wool? The source of merino wool is merino sheep a breed that originated centuries ago in Spain. Merino is much finer than traditional wool, and is technically more complex than synthetics. Merino wool fibers range between 15 to 24 microns in diameter, with 17.5-micron fibers (rated “ultrafine”) often used for next-to-skin apparel. The merino industry regards 18.5 microns as the average fiber diameter most people can wear without experiencing an itchy sensation. Merino is the most hydrophilic of all fibers and can absorb and release 10x more moisture than synthetics. Each fiber can absorb up to one third of its own weight in moisture without feeling clammy or wet to touch.
Outdoor enthusiasts should look for a quality, washable wool when building layers against the cold. Look for washable wool there’s a lot of good companies that make it.
To read more see REI “How to Choose Wool Clothing“ or Discover the Warmth of Wool .