This animal fiber is derived from the hair of sheep or lamb. Wool fiber dates back 10,000 years when early man in Central Asia discovered that the hair from animal skins, which were already being used to provide warmth, could be formed into yarn and then woven to form fabric. The technique spread and ancient Egyptians were known to have popularized its use as early as 4000 B.C.E.
The processing of wool yarn involves cleaning or scouring the wool to extract impurities and then carding it, which produces a continuous strand of yarn before it is twisted. The combing process yields a smoother more lustrous yarn such as those used to make worsted wool fabric. The yarn is then spun and twisted to create the desired thinness before it is dyed to the desired color. Once wool yarn is woven it must be finished to control shrinkage and smooth out the wrinkles.
Wool fiber is measured in microns, with 1 micron measuring the equivalent of 1/20,000th of an inch in diameter. The finest wool yarns, such as those used in underwear, measure between 10-20 microns in diameter and are taken from fleece taken from the animal's shoulders and sides.
Wool is one of the most popular fabrics in the industry today because of its warmth, resiliency, comfort, and flame resistance.
Historical Dictionary of the Fashion Industry. Francesca Sterlacci and Joanne Arbuckle.