Wool is the textile fiber obtained from sheep and certain other animals, including cashmere from goats, mohair from goats, qiviut from muskoxen, angora from rabbits, and other types of wool from camelids.
Wool has several qualities that distinguish it from hair or fur: it is crimped, it is elastic, and it grows in staples (clusters).
Wool is the dense, warm coat of sheep, also called a fleece. The hair of sheep has many unique properties that make it well suited to textile production, something humans realized approximately 8000 BCE, when sheep first began to be domesticated. Wool is used in a variety of textiles and can be found woven or knitted.
This material is highly flame resistant, and frequently used for mattresses and rugs for that reason. It is also highly durable, able to stretch up to 50% when wet and 30% when dry. In addition, wool has excellent moisture wicking properties, pulling moisture into the core of the fiber so that it doesn't feel wet or soggy to the wearer. It pulls moisture away from the skin, as well, and is worn by people in a wide variety of situations who prefer the feeling of dry air next to the skin to the clammy sense of perspiration.
Wool is favored for textile production because it is easy to work with and takes dye very well. The springy fibers remember shapes when well cared for. Furthermore, it takes to felting, a process in which fibers interlock into a tight mat, very well. Felt is used as insulation, for arts and crafts projects, and for decorative accents.
Production starts with the shearing of the sheep, which usually happens once a year. A skillful shearer can remove the entire fleece at once with long flowing strokes, keeping the fibers long. After shearing, the wool is washed to remove impurities. One of these impurities islanolin, which is used in many cosmetics.
After washing, many producers combine wools for a specific blend and dye them together, so that the dye will take evenly, before carding it through a set of teethed rollers. Carding pulls the fibers straight, while removing any remaining dirt or vegetable matter. The wool is pulled into slivers, long strips of fibers loosely pulled together and running in the same direction. If, after carding, the wool is under 3 inches (almost 8 centimeters), it is twisted into rovings, rope like strands that can be spun for knitting. If the strands are longer, they must be combed and drawn before spinning.
Spinning pulls the fibers tightly together and twists them so that they retain a long yarn shape. Yarn can be spun in all sorts of thicknesses and gauges, depending upon the intended use. For wool weaving, the yarn tends to be very fine. For knitting, it may be quite chunky. There are myriad uses for wool, a highly versatile textile. For example, shorter, coarse wool will turn into carpeting, while medium length material will be used in suits.
After knitting or weaving, the wool is often shrunk through a controlled process so that it won't shrink excessively for the end user. Most knits are also blocked on forms to set a shape, and many products are also brushed for a specific finish.
Proper care for wool begins with following the label directions. In general, it should be allowed to rest between wearings, to retain its shape. It should never be compressed or stored on hangers, which will stretch it. Brushing wool will remove surface soil and stains before they are ground in, and a slightly damp cloth will remove deeper stains. The material should be dried flat at room temperature, not exposed directly to heat.
Wool is the fiber that grows on the body of most sheep. It replenishes itself each time the sheep is sheared and continues to grow throughout the sheep's lifetime.
Wool is an extremely complex protein, evolved over millions of years for the protection of warm blooded animals in a great variety of climates and conditions. By comparison, synthetic fibers are simple, having been designed for specific limited uses.
Wool fiber is so resilient and elastic that it can be bent 30,000 times without danger of breaking or damage. Every wool fiber has a natural elasticity and wave or crimp that allows it to be stretched as much as one-third and then spring back into place. Its complex cellular structure also enables it to absorb moisture vapor, but repel liquid. No synthetic fiber has been able to combine all of these characteristics.
Wool absorbs many different dyes deeply, uniformly and directly without the use of chemicals. Because of this ability, wool is known for its beautiful, rich colors.
Warm and cool
Wool is comfortable to wear in both warm and cool climates. This is because wool is an absorbent fiber. When the air is cool and damp, wool absorbs moisture and keeps a layer of dry insulating air next to the skin. When it is warm, that same absorption capacity takes up perspiration and keeps insulating dry air next to the skin, making the body's natural cooling system work better.
Wool garments are a great investment. Since wool fibers resist piling, snagging, and breaking, wool garments typically outlast synthetic sweaters. Furthermore, since wool fibers are naturally elastic, wool garments don't wrinkle, bag, or sag as other fabrics.
Because of its unique properties, wool has many other uses besides clothing: blankets and rugs. Wool can be used to clean up oil and chemical spills. Wool mulch is easier to lay and more aesthetic than black plastic, plus it's biodegradable. As an insulation material, wool has an R value of 3.5 per inch of thickness and is more environmentally-friendly.
Wool is the only fiber that naturally resists flaming. Unlike many artificial fibers which melt and stick to the skin when on fire, wool usually smolders or chars instead of bursting into flame. Although wool will burn under intense fire, it normally self-extinguishes when the flame source is removed. For safety reasons, many airlines use wool or wool blends for the upholstery fabric on their seats. Wool is favored by the U.S. military
Worsted vs. woolen
Most wool is made into yarn using either the worsen or woolen system. Worsted yarn consists of long fibers that lie parallel, so that the materials made from it are smooth and lean and stronger than woolens. In woolen yarn, there are long and short fibers lying in different locations, so the woolen fabrics on the whole are harsher to the touch, more rugged to look at, and warmer than worsteds.
The "Itch" factor
The itchiness of wool that some people experience is related to fiber diameter. Finer fibers, such as pure Merino wool, give greater comfort. The comfort limit for garments worn next to the skin is 28 microns. Many people experience discomfort if more than 3 to 4 percent of the fibers are over 28 microns thick. Wool can be treated with chemicals or blended with other fibers to remove the itch factor. Some wools, such as SmartWool® are guaranteed not to itch.