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Wool is perhaps the most useful of all fibres. It is a warm fibre and thus particularly suitable for outer clothing and underwear. Wool varies greatly in quality. Some types consist of short coarse fibres while others are very fine and long. Wool fibres also vary considerably in luster. These variations depend on differences in the breed of sheep and whether the sheep is sheared alive or dead. Most wool fabrics and garments shrink when washed for the first time. With additional washings further shrinkage takes place and this is accompanied by a matting or felting. Felting continues with further washing until the fibres are packed to a maximum degree in the fabric. Although wool is the most important animal fibres, there are other hair fibres which are of considerable commercial value. These come mostly from animals of the goat and camel families. The Angora goat, which originated in Turkey, has a coat of long, lustrous hair. This hair provides the textile fibres known as mohair. Camel hair is also used as a textile fibre. Camel hair fabrics are warm and comfortable. They are used for making overcoats, dressing gowns and knitted goods. Llama, alpaca, guanaco belong to the camel family. The surface of the cotton fibre, seen at high magnification, is wrinkled. But for most practical purposes, cotton can be regarded as having a smooth surface. Cotton fibres have a natural luster. The smooth, hard primary coat of cellulose contains waxes which contribute to the luster of the fibre. The colour of cotton, normally creamy-white, is affected greatly by the conditions under which it is produced. It may turn grey or bluish-white or it may darken to a buff colour. Cotton is a relatively inelastic, rigid fibre. Cotton does not stretch easily. Absorption of water by the cotton cellulose results in an increase in fibre strength. Fibres saturated with water are about 20 per cent stronger than dry fibres. Cotton has an excellent resistance to degradation by heat. Cotton burns readily in air. Cotton shows only a small loss of strength when stored carefully. Ancient samples of cotton fabric taken from the tombs more than 500 years old had 4/5 of strength of new material. There is a gradual loss of strength when cotton is exposed to sunlight, and the fibre turns yellow. Much of the damage is caused by ultra-violet light and by the shorter waves of visible light. The cotton can be protected by using suitable dyes. Chemical fibres are of great industrial importance. The first successful attempts to obtain man-made fibres were done at the beginning of the century. Chemical fibres now being produced are subdivided into rayons (or regenerated fibres) and synthetic fibres. Production of rayons requires some naturally occurring organic raw material as the starting point. Rayons are remanufactured or regenerated from cellulose and natural proteins of milk, soybeans, corn etc. Viscose is the most widespread regenerated fibre. Synthetic fibres are built up by chemical methods from the atoms of coal, water or air. This process is called synthesis. Having been originally developed as a substitute of natural fibres, now man-made fibres reveal some properties which surpass those of natural fibres. For example, all man-made filaments are resistant to insects, they absorb little moisture. Being not proof against heat, synthetic fabrics cannot be boiled. When cut to staple chemical fibres are mixed with natural fibres. This increases durability and wearing qualities of such textiles.

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