Characteristics

The amount of crimp corresponds to the thickness of the wool fibers. A fine wool like Merino may have up to a hundred crimps per inch, while the coarser wools like karakul may have as few as one to two crimps per inch. 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.

Wool fibers are hygroscopic. This means wool has the power to readily absorb and give off moisture. It 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 fibers and some synthetics. It has lower rate of flame spread, low heat release, and low heat of combustion; doesn't melt or drip; forms a char which is insulating and self-extinguishes; 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.

Wool is static resistant as the retention of moisture within the fabric prevents a build up of static. Wool garments are much less likely to spark or cling to the body. The use of wool car seat covers or carpets reduces the risk of a shock when a person touches a grounded object. Wool is considered by the medical profession to be hypoallergenic.

Processing

main: Sheep shearing

After shearing, the wool is separated into five main categories: fleece (which makes up the vast bulk), broken, pieces, bellies, and locks. The latter four are pressed into wool packs and sold separately. The quality of fleece is determined by a technique known as wool classing, whereby a qualified wool classer groups wools of similar gradings together to maximise the return for the farmer or sheep owner. Prior to Australian auctions, 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.