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From Fibres To Fabrics

Published in: Science
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    Sohail

    • Kolkata
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An introductory class notes on Fibres and Fabrics with sample solved exercises for middle school students

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    Chapter Summary We all know that our clothes are made from fibres obtained from plants and animals. Fibres are long, narrow, thin, tubular structures obtained from plants and animals. Plant fibres include cotton, jute and coconut while silk and wool are important animal fibres. wool Wool is the fibre obtained from the fleece of the domestic animals like sheep, goat, yak, etc. Besides domesticated sheep, wool can also be obtained from the hair of camel and some goats like Angora and Llama. Such fibres are quite expensive, since they are collected by combing and not by fleecing. Wool is generally creamy in colour, but also black, brown or grey coloured wool is found. Wool can be dyed in different colours. The world's finest wool is obtained from the fleece of merino sheep. Wool has been used as a clothing material by some of the earliest civilizations as sheep have been bred since ancient times. In Roman times, wool was the chief clothing material along with linen and leather, as silk imported from China was expensive and cotton produced in India was unknown there. In medieval times, wool became the chief trading material all over the world. Today, Australia is the largest producer of raw wool in the world. Steps in the production of wool — 1. 2. 3. 4. 5. 6. Shearing the removal of wool from a sheep's body done manually by a razor or mechanically by a shearing machine. The sheep are sheared once every year. A good quality sheep provides about 4.5 kg of fleece per year. Sorting and Grading Fleece (raw wool) is sorted manually to remove stained, damaged or inferior wool. The sorted fibres are mainly graded on the basis of their strength, fineness, length, crimp and colour. Scouring Fleece is scoured with some soap or detergent to remove yolk and suint, the dried perspiration of the sheep. This is done to remove dust, dirt and grease from it. Carding the scoured wool fibres are dried and disentangled by means of rollers which have thin wire teeth. These rollers arrange the fibres into a flat sheet of thin straight fibres called web. The web is processed into narrow ropes known as sliver. The whole process is called carding. Blending and dyeing — the clean wool obtained from all sources is blended mechanically at this stage. The fibres are then dyed in various colours. Spinning the spinning machines spin or twist the fibres into thread or yarn. It is now ready to be taken to the mills for being woven or knitted. There are two types of woolen yarns — woolen yarns and worsted yarns. Woolen yarn is spun from short coarse wool fibres. It is bulky, has a rough surface and is heavier. It is mainly used to make fabrics for jackets, coats, shirts, blankets and upholstery. The worsted yarn is spun from fine, long fibres and is very smooth and fine. They are strong and are expensive. They are used for suiting, trousers, etc. Wool is marketed worldwide by International Wool secretariat (IWS) based at UK. It assigns the wool-mark sign to garments certifying that it is made of pure wool.
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    Silk Silk is a protein fibre obtained from silkworms. The silkworm spins thread like filaments around itself to form a cocoon. Silk fibres have shimmering appearance because of their prism-like structure which causes refraction of light at various angles. Silk is highly prized because of its natural lustrous appearance. The credit of developing silk from cocoons goes to the Chinese Empress Xi-Ling-Shi who lived in about 3000 BC. From China the art of silk-making spread throughout Asia, Europe and North Africa. Silk production was practiced in India as early as 300 AD. Life Cycle of a Silk Worm A silk worm starts its life as a tiny egg laid by a female moth. The incubation is the first stage that lasts for about 10-14 days. The egg hatches into larva or caterpillar. It feeds on mulberry leaves. This stage lasts for about 27 days. The next stage is pupa, when the caterpillar spins a beautiful oval white or yellow cocoon. The pupa stage lasts for about 14 days. After 2-3 weeks a creamy white adult moth emerges from the cocoon. It is the adult stage of the silk worm. Rearing of silkworms for commercial purpose is called sericulture. It is a lengthy and a complex process. After the silk worms form cocoon they are boiled in water to kill. After the cocoons are dried and brushed to remove the outer coarse portion. Around four to eight filaments are twisted together to make a thread which is wound on reels. Approximately 5500 cocoons are used to produce 1 kg of raw silk. Silk is processed in four ways — thrown singles, organize, crepe and tram. To manufacture silk fabrics, generally organize thread is used for warp (the thread arranged lengthwise on the loom) and tram thread is used for weft (the thread spread across the warp). Crepe thread is used to manufacture crinkly silk fibres and thrown singles are used to produce sheer silk fabrics. Uses of Silk silk fibres are suitable for all seasons and is very strong and lustrous. They are expensive fibres and are worn on special occasion. In addition to fabrics, silk is also used in the making of parachutes, bulletproof vests and even bicycle tyres. 3 Respiratory disease and skin infections are associated with the sericulture industry. Solved Exercise Al. Write any three important uses of silk and wool. Ans: Silk is used for making expensive fibres like dresses, sarees and scarfs. It is also used in the making of parachutes, bulletproof vests and bicycle tyres. Wool is mainly used to make fabrics for jackets, coats, shirts, blankets and upholstery and for suiting, trousers, etc. A2. What is sliver?
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    Ans: The narrow ropes of finished wool obtained from the thin straight fibres, after the carding process is called sliver. A3. How is raw silk obtained from cocoons? Ans: Silk worms are harvested after they form the cocoons by boiling them in water and killing the caterpillars. In this process, the gum sericin is dissolved in water and silk fibres are set free. The cocoons are dried and brushed to remove the outer coarse portion. Around four to eight filaments are twisted together to make a thread which is wound on a reel, giving us the raw silk for making silk fibres. After this the raw silk is dyed into various colours. A4. What is sericulture? Ans: Sericulture is the rearing of silkworms for commercial production of silk. It is a lengthy and complex process. A5. What is carding? How is woolen yarn processed from carded wool? Ans: The process of formation of sliver, the processed narrow woolen ropes from raw wool is known as carding. The carded wool is blended mechanically and is dyed in various colours. Then the spinning machines spin or twist the fibres into thread or yarns. A6. What is a web? Ans: Web is a flat sheet of thin straight fibres of wool which is obtained from a carding machine. A7. How is silk fibre harvested? Ans: Silk worms are harvested after they form the cocoons by boiling them in water and killing the caterpillars. In this process, the gum sericin is dissolved in water and silk fibres are set free. The cocoons are dried and brushed to remove the outer coarse portion. A8. What are the different kinds of silk threads produced during the processing of silk? Ans: The processing of raw silk produces four types of silk threads thrown singles, organize, crepe and tram. Thrown singles are twisted in only one direction and is used to produce delicate and fine fabric. Organize is twisted in one direction followed by two or three more threads in opposite direction. It is used for heavy fabrics. Crepe is also produced by twisting the singles in the same way as organize, but it is twisted to a greater extent. Tram consists of two or more raw silk threads twisted in only one direction, with 8 to 12 turns every cm. A9. What do you know about the history of silk? Ans: The credit of developing silk from cocoons goes to the Chinese Empress Xi-Ling-Shi who lived in about 3000 BC. From China the art of silk-making spread throughout Asia, Europe and North Africa. Silk production was practiced in India as early as 300 AD. It is also believed that
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    some monks brought silk worm eggs to Constantinople in hollow canes from China and by 13th Century, Italy had become the centre of the world silk trade. In America, King James I of England introduced silk production but soon the trade was finished because the silk worms couldn't survive the American and English climates. A 10. Which states of India are the main producers of silk? Ans: The Indian sericulture industry is chiefly concentrated in the states like Karnataka, Tamil Nadu, Andhra Pradesh, Assam and West Bengal. Fill in the blanks: Bl. Wool is mostly obtained from the hairs of sheep and goats B2. Silk is generally obtained from the cocoon of silkworms B3. Fleece contains hair which is known as kemp B4. Wool fibres have scales and crimps B5. The most widely used species of silkworm used for sericulture is called Bombyx mori B6. The dried perspiration of sheep is known as suint B7. The finest kind of wool is obtained from merino sheep Australia is the world's largest producer of wool B8. B9. Wool is marketed worldwide by International Wool Secretariat (IWS)

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