Wool is a fiber that comes from the fleece of sheep and some other animals. It is made into durable fabrics used in manufacturing blankets, clothing, rugs, and other items. Wool fabrics clean easily, and they resist wrinkles and hold their shape well. Wool also absorbs moisture and insulates against both cold and heat. All these features make wool popular for coats, sweaters, gloves, socks, and other clothing.
Wool fibers are nearly cylindrical in shape. Overlapping scales on the surface make the fibers mat and interlock under heat, moisture, and pressure. This property of wool fibers is called felting. Felting increases the strength and durability of wool fabrics. It also enables wool to be made into felt.
The Wool Products Labeling Act of 1939 established guidelines in the United States for defining and labeling wool products. This law defines wool as the fiber from the fleece of sheep. It also includes such fibers as alpaca, from alpacas; camel's hair; cashmere, from Cashmere goats; mohair, from Angora goats; and vicuna, from vicunas.
Worldwide production of raw wool totals about 61/2 billion pounds (3 billion kilograms) annually. The leading wool-producing nation is Australia. Every state in the United States produces some wool. Texas is the leading producer, followed by the states of Wyoming, California, Montana, and Colorado, in that order. The United States uses more wool than it produces. Thus, it must import some wool.
Sources of wool. Almost all wool comes from sheep. These animals--and their wool--are classified into five groups, depending on the quality of the fleece. The five classifications of wool, which are listed here in order of quality, are (1) fine wool, (2) crossbred wool, (3) medium wool, (4) long wool, and (5) coarse wool, or carpet wool.
Fine-wooled sheep include the Merino and other breeds with Merino ancestry, such as the Debouillet and the Rambouillet. These types of sheep produce the finest wool, which is used in making high-quality clothing.
Crossbred-wooled sheep, such as the Columbia and Corriedale, are crossbreeds of fine- and long-wooled breeds. Their wool is used for rugged clothing.
Medium-wooled sheep provide wool used in making industrial and upholstery fabrics. Cheviot, Dorset, Hampshire, Oxford, Shropshire, Southdown, and Suffolk sheep are in this group.
Long-wooled sheep include the Cotswold, Leicester, Lincoln, and Romney. They produce wool used for carpets and industrial fabrics.
Coarse-wooled sheep include the Karakul and Scottish Blackface. The wool of these animals is used mostly for carpets and handicraft yarns.
Types of wool are determined by the quality of a sheep's fleece. The quality depends on the age and physical condition of the animal and by the climate in which it lives. The fleece of a healthy sheep is covered by an oily substance called yolk. Yolk consists of wool grease and suint (dried perspiration). It protects the sheep from rain and keeps the fleece from becoming matted.
Young sheep produce the best wool. The softest and finest wool, called lamb's wool, comes from 6- to 12-month-old sheep. Hog wool, also called hogget wool, is the first fleece sheared from a sheep that is 12 to 14 months old. After a sheep has been sheared for the first time, its wool is called wether wool.
Lower quality wool comes from dead or diseased sheep. Sheep that have been slaughtered for their meat provide pulled wool, sometimes called skin wool or slipe wool. Dead wool is taken from sheep that have died of disease or have been killed by other animals. Aged sheep have matted and tangled fleeces that provide cotty wool. Fleeces soiled by manure or dirt are called tag locks in the United States and stain pieces in England and Australia.
The United States Federal Trade Commission, which administers the Wool Products Labeling Act, classifies wool into two categories. Virgin wool, or new wool, has never been spun into yarn or made into felt. Some fabrics are made of fibers that have been reclaimed from previously spun or woven wool. Recycled wool is the name given to these products. Fabrics made from recycled wool are sometimes called shoddy.
Processing of wool involves four major steps: (1) shearing, (2) sorting and grading, (3) making yarn, and (4) making fabric.
Shearing. Most sheep shearers use power shears, and experts can clip 200 or more animals a day. They remove the fleece in one piece so the various parts can be easily identified for sorting and grading. Different parts of a fleece vary in quality. For example, the best wool comes from the shoulders and sides of the sheep.
In most parts of the world, sheep are sheared once a year, in spring or early summer. But in some regions, the fleeces may be cut off twice yearly.
Sorting and grading. Workers remove any stained, damaged, or inferior wool from each fleece and sort the rest of the wool according to the quality of the fibers. Wool fibers are judged not only on the basis of their strength, but also by their (1) fineness (diameter), (2) length, (3) crimp (waviness), and (4) color.
In the United States, the fineness of wool fibers is determined by comparing them to the fineness of Merino wool. In England, fineness depends on the number of fibers per inch. In Australia, the diameter of the fibers is generally measured in units called microns. A micron equals a millionth of a meter (. 000039 inch).
Fiber length is important in determining what processes will be used to make yarn and fabric. Carding length fibers, also called clothing length fibers, measure less than 11/2 inches (3.8 centimeters) long. French combing length fibers range from 11/2 to 21/2 inches (3.8 to 6.4 centimeters) in length. Combing length fibers are more than 21/2 inches (6.4 centimeters) long.
The natural crimp of wool provides the fibers with elasticity. This property enables wool fabrics to hold their shape after being stretched or twisted. The best wool fibers have many evenly spaced waves.
The color of most wool ranges from white to dark ivory. White wool is the most desirable because manufacturers may have to bleach darker wool before it can be dyed.
Making yarn. The wool is scoured with detergents to remove the yolk and such impurities as dust and sand. Wool grease from the yolk is processed into lanolin, a substance used in hand creams and other cosmetics.
After the wool dries, it is carded. The carding process involves passing the wool through rollers that have thin wire teeth. The teeth untangle the fibers and arrange them into a flat sheet called a web. The web is then formed into narrow ropes known as slivers.
After carding, the processes used in making yarn vary slightly, depending on the length of the fibers. Carding length fibers are used in making woolen yarn. Combing length and French combing length fibers are made into worsted yarn. The processes used for the two kinds of yarn are similar. But worsted slivers go through an additional step called combing, which removes impurities and short fibers.
After carding or combing, the slivers are stretched and slightly twisted to form thinner strands called roving. Spinning machines then twist the roving into yarn. Woolen yarn is bulky and fuzzy, with fibers that lie in different directions. Worsted yarn is smooth and highly twisted, and its fibers are parallel.
Making fabric. Wool manufacturers knit or weave yarn into a variety of fabrics. They use woolen yarns in making flannel, homespun, melton, Saxony, Shetland, and tweed fabrics. Worsted yarns are used for such fabrics as broadcloth, crepe, gabardine, serge, sharkskin, twill, and whipcord. Almost all wool fabrics except felt are made from yarn (see FELT).
Wool may be dyed at various stages of the manufacturing process. If the fibers are dyed before spinning, the process is called stock dyeing or top dyeing. If they are dyed after being spun into yarn, it is called yarn dyeing, package dyeing, or skein dyeing. If the dyeing does not take place until the fabric has been made, it is known as piece dyeing. Most fabrics with fancy designs are stock dyed or yarn dyed. Piece dyeing is used for solid-colored fabrics. See DYE.
All wool fabrics undergo finishing processes to give them the desired appearance and feel. The finishing of fabrics made of woolen yarn begins with fulling. This process involves wetting the fabric thoroughly with water and then passing it through rollers. Fulling makes the fibers interlock and mat together. It shrinks the material and gives it additional strength and thickness. Worsteds go through a process called crabbing, in which the fabric passes through boiling water and then cold water. This procedure strengthens the fabric.
Some wool fabrics tend to shrink when dry-cleaned. To prevent such shrinkage, some manufacturers preshrink the fabric. One popular process, called London Shrinking, uses water and pressure to shrink the fabric. After the various finishing processes, the fabric is made into clothing and other products.
History. About 10,000 years ago, people in central Asia began to raise sheep for food and clothing. The art of spinning wool into yarn developed about 4000 B.C. and encouraged trade among the nations in the region of the Mediterranean Sea. Merino sheep were developed in Spain by A.D. 100. Spain was the only source of these sheep until the 1700's.
The first wool factory in England was established about A.D. 50 in Winchester by the Romans. The wool industry soon played a major part in the nation's economy. By 1660, the export of wool fabrics accounted for about two-thirds of England's foreign trade.
In the early 1500's, explorers from Spain brought sheep to what is now the United States. England discouraged the wool industry's growth in the American Colo-nies so the colonists would have to rely on English goods. But the colonists smuggled sheep from England. By the 1700's, spinning and weaving were flourishing in America.
In 1797, the British brought 13 Merino sheep to Australia and started the country's Merino sheep industry. Spain first sold Merino sheep to the United States in the early 1800's. Americans bred these animals with descendants of the sheep that had been brought from England. In the 1800's, many pioneers brought sheep with them while traveling to the West. As a result, the production of wool and wool fabrics spread to nearly all parts of the United States.