Wool is the textile fiber obtained from sheep and certain other animals, including cashmere from goats, mohair from goats, qiviut from muskoxen, vicuña, alpaca, and camel.

Wool's scaling and crimp make it easier to spin the 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. Insulation also works both ways; Bedouins and Tuaregs use wool clothes to keep heat out.

The amount of crimp corresponds to the fineness of the wool fibers. A fine wool like Merino may have up to 100 crimps per inch, while the coarser wools like karakul may have as few as 1 to 2. Hair, by contrast, has little if any scale and no crimp, and little ability to bind into yarn. On sheep, the hair part of the fleece is called kemp. The relative amounts of kemp to wool vary from breed to breed, and make some fleeces more desirable for spinning, felting, or carding into batts for quilts or other insulating products including the famous Tweed (cloth) cloth of Scotland.

Wool fibers are hydrophilic, meaning they readily absorb moisture. Wool fibers are hollow.  Wool can absorb moisture almost one-third of its own weight.  Wool absorbs sound like many other fabrics. Wool is generally a creamy white color, although some breeds of sheep produce natural colors such as black, brown, silver, and random mixes.

Wool ignites at a higher temperature than cotton and some synthetic fibers. It has lower rate of flame spread, low heat release, low heat of combustion, and does not melt or drip; it forms a char which is insulating and self-extinguishing, and contributes less to toxic gases and smoke than other flooring products, when used in carpets.  Wool carpets are specified for high safety environments, such as trains and aircraft. Wool is usually specified for garments for fire-fighters, soldiers, and others in occupations where they are exposed to the likelihood of fire.

Shearing

Sheep shearing is the process by which the woollen fleece of a sheep is cut off. After shearing, the wool is separated into four main categories: fleece (which makes up the vast bulk), broken,bellies, and locks.  The quality of fleeces is determined by a technique known as wool classing, whereby a qualified person called a wool classer groups wools of similar gradings together to maximize the return for the farmer or sheep owner. In Australia & New Zealand, before being auctioned all Merino fleece wool is objectively measured for micron, yield (including the amount of vegetable matter), staple length, staple strength, and sometimes color and comfort factor.

Scouring

Wool straight off a sheep, known as "greasy wool"[8] or "wool in the grease", contains a high level of valuable lanolin, as well as dirt, dead skin, sweat residue, pesticide, and vegetable matter. Before the wool can be used for commercial purposes, it must be scoured, a process of cleaning the greasy wool. Scouring may be as simple as a bath in warm water, or as complicated as an industrial process using detergent and alkali, and specialized equipment. In commercial wool, vegetable matter is often removed by chemical carbonization.  In less processed wools, vegetable matter may be removed by hand, and some of the lanolin left intact through use of gentler detergents. This semi-grease wool can be worked into yarn and knitted into particularly water-resistant mittens or sweaters, such as those of the Aran Island fishermen. Lanolin removed from wool is widely used in cosmetic products such as hand creams.

Production

Global wool production is approximately 1.3 million tonnes per year, of which 60% goes into apparel. Australia is the leading producer of wool which is mostly from Merino sheep. New Zealand is the second-largest producer of wool, and the largest producer of crossbred wool. China is the third-largest producer of wool. Breeds such as Lincoln, Romney, Tukidale, Drysdale and Elliotdale produce coarser fibers, and wool from these sheep is usually used for making carpets. In the United States, Texas, New Mexico and Colorado have large commercial sheep flocks and their mainstay is the Rambouillet (or French Merino). There is also a thriving home-flock contingent of small-scale farmers who raise small hobby flocks of specialty sheep for the hand spinning market. These small-scale farmers offer a wide selection of fleece.

Wool Pricing

The quality of wool is determined by the following factors, fiber diameter, crimp, yield, colour, and staple strength. Fiber diameter is the single most important wool characteristic determining quality and price.