I.

Introduction

Wool, common name applied to the soft, curly fibers obtained chiefly from the fleece of domesticated sheep, and used extensively in textile manufacturing. Wool may be differentiated from hair mainly by the nature of the scales that cover the outer surface of each fiber. Wool scales are numerous, minute, and pointed and are attached only at their bases; thus the fibers interlock under pressure (see Felt). The number of scales varies with the fineness and curliness of the fiber. Because of its crimp, or curl, wool has considerable resilience. This quality, together with its high tensile strength and elasticity, gives fine woolen fabrics the ability to retain shape better than cloth made from other natural fibers. Other characteristics of wool, which make it especially desirable for clothing, are its lightness, its ability to absorb moisture, and its insulating properties.

II.

Sources of Wool

Wild species of sheep have a short, woolly undercoat covered by long, coarse, straight hair. The hair has entirely disappeared in domestic breeds; selective breeding has improved both the quality and abundance of wool. Wool production of sheep is also influenced by nutrition, climate, and care. Neglected domesticated animals have a tendency to produce hair instead of wool.

The fleece of sheep raised for wool is generally shorn once yearly, in the spring or early summer. In regions where the climate is warm throughout the year, shearing may occur twice annually. The fleece is cut close to the skin, usually with mechanical shears, and removed in one piece. The average weight of the fleece shorn from better wool-producing breeds is about 4.5 kg (about 10 lb). Small amounts of wool come from the skins of lambs slaughtered for meat.

Wool from different parts of the same fleece varies greatly in length of fiber, fineness, and structure. Wool from the shoulders and sides of the sheep is usually superior to that from other parts of the body. Quality varies also with the different breeds of sheep. Pure merino sheep bear the finest wool, and this type has been crossed with hardy sheep producing longer, coarser wool. About 40 percent of the world's total wool production consists of merino wool, and about 43 percent is obtained from crossbred varieties. The remainder is composed largely of carpet wools, which are derived mostly from special types of sheep and are employed in the manufacture of blankets, carpets, and tapestries. In addition, a small quantity of fine wool used for apparel is obtained from animals other than sheep. These wool-bearing animals include the camel, the alpaca, the Angora and Kashmīr goats, the llama, and the vicuña.

III.

Types and Labeling of Wool

The value of wool on the market depends primarily on fineness and length of fiber. Strength, elasticity, amount of crimp, and uniformity are also considered. Two different systems are followed in wool processing, the woolen system and the worsted system. In the woolen system, the fibers are carded and then spun. In the worsted system, the fibers proceed to a combing process, which separates the long from the short fibers. The long fibers are then formed into smooth compact strands ready for spinning into yarn. Worsteds are not napped but are finished with a smooth surface. Uniform lengths of relatively fine fibers are very important in the worsted system, because short fibers are difficult to spin. In the woolen system, on the other hand, fibers of mixed lengths may be used. Fine wools are classified according to the length of fiber. Longer fibers used in the manufacture of worsteds are called combing wool; shorter fibers employed for yarns used in soft, woven fabrics are known as carding wool.

In 1939, to protect the consumer, the U.S. Congress passed the Wool Products Labeling Act. This law requires that all fabric containing wool carry identification indicating the percentage of wool in the cloth. The act also specifies the proper legal description for the fiber according to category, such as new, reprocessed, or reused wool. New wool, or virgin wool, is wool that never before has been used in manufacture. Reprocessed wool refers to fiber reclaimed from woven scraps and clips accumulated from the cutting table, from samples, and from mill ends. These remnants, never previously used, are reconverted into a fibrous state and then reprocessed into the manufactured product. Reused wool is wool fiber recovered from products used by consumers, respun, and rewoven. This category is less important now than formerly, because of competition from synthetics.

IV.

Wool Production

Australia is the world's largest producer of raw wool, growing about 30 percent of the total world supply. Other leading producers are China, New Zealand, Iran, the United Kingdom, Argentina, South Africa, and Uruguay. In 2005 annual U.S. wool production was 16,885 metric tons when weighed before cleaning; most of the wool came from sheep raised in Texas, Wyoming, California, Colorado, Montana, and South Dakota. All the carpet wool and more than one-half of the apparel wool consumed in U.S. mills is imported from other countries.

V.

Wool Manufacturing

The first step in the processing of wool preparatory to cloth making is the sorting of the fibers. As each fleece is pulled apart, the fibers are sorted into separate piles of similar nature and characteristics, mainly on the basis of fineness, length, and freedom from defects. After sorting, the fibers are cleaned, because wool contains an oily substance, called yolk, consisting of lanolin and suint, which is dried perspiration. The wool is scoured by a soap-alkali preparation or other detergent or solvent to remove the grease and other foreign substances.

The scoured wool fibers are disentangled and drawn straight into a continuous form in a process called carding, which employs a carding machine. In this process, the fibers are passed between pairs of rotating cylinders covered with a material called card clothing, which contains fine, pliable wire teeth. The wool emerges from the rollers in the form of a thin film known as the web. The processing of the web varies according to whether woolen or worsted yarn is to be produced.

Woolen fabrics, such as tweeds, are woven from bulky yarns containing short wool fibers arranged at random, so that the fabric is relatively thick and has a fuzzy surface. Worsted fabrics, such as gabardines, are woven from yarns composed of longer, thinner wool fibers, tightly twisted for a smooth surface.

For the production of woolen yarn, the web is split into soft, thin strands called roving, and then it is ready to be spun. For worsted yarn, the web is processed by machines that straighten the fibers, make them parallel, and remove all the short pieces. The resultant thick strand is then condensed by passing it through several machines until a very thin strand of worsted roving is obtained. From this type of roving can be spun the smooth yarn that produces firm, smooth-textured worsted fabrics. See Spinning.

See also Cashmere; Rugs and Carpets; Textiles.

Contributed by: The Wool Bureau, Inc. New York City