• NCERT नवा अभ्यासक्रमनु BEST मटेरियल ALL IN ONE
  • 22 August 2018

    NCERT STD 7 SCIENCE UNIT 3 FIBER TO FABRIC UNIT TEST PDF FILE

    Animal fibres

    → Wool and silk fibres are obtained from animals.

    → Wool is obtained from the fleece (hair) of fleece sheep or yak.

    Silk fibres come from cocoons of the silk moth.

    Wool

    → Wool comes from sheep, goat, yak and some other animals who are having hair on their body.

    → Wool is derived from these hairy fibres.

    Animals that yield wool

    → Breeds of sheep are found in different parts of our country are the main source of obtaining wool.


    • Yak wool: Obtained from Yaks which is common in Tibet and Ladakh.
    • Angora wool: Obtained from Angora goats found in hilly regions such as Jammu and Kashmir.
    • The under fur of Kashmiri goat is soft which is woven into fine shawls called Pashmina shawls.
    • The fur (hair) on the body of camels.
    • Llama and Alpaca, found in South America.
    Rearing of Sheep and obtaining fibre
    • Sheep are reared in hilly areas of Jammu & Kashmir, Himachal Pradesh, Uttaranchal, Arunachal Pradesh and Sikkim or the plains of Haryana, Punjab, Rajasthan and Gujarat.
    • Sheep are herbivores so mainly feed on grass and leaves. They are also provided pulses, corn, jowar, oil cakes and other materials.
    • In winter, sheep are kept inside and fed leaves, grass and dry fodder.
    • Sheep having thick coat of hair on their body yields good quality wool in large quantities.
    • Hair of sheep is shaved off for getting wool, once the reared sheep have developed a thick growth of hair.
    List of India breeds of sheep
    Processing of Wool from Fibre
    → Obtaining wool is very long process which involves various steps.
    Step 1(Shearing)
    → Fleece of the sheep along with a thin layer of skin is removed from its body which is called Shearing.
    → Shearing is done during hot weather so that sheep survive without protective hair.
    →The hair or the fleece of the sheep are dead cells so it doesn't hurt the sheep.
    → The instrument used to remove the fleece is similar to the shaving instrument.
    Step 2 (Scouring)
    → Washing of sheared skin with hair in tanks to remove grease, dust and dirt is called scouring. Nowadays scouring is done by machines.
    Step 3 (Sorting)
    → The hairy skin is sent to a factory where hair of different textures are separated or sorted. This is called sorting.
    Step 4
    → The small fluffy fibres, called burrs, are picked out from the hair. These are the same burrs which sometimes appear on your sweaters. 
    →The fibres are scoured again and dried. This is the wool ready to be drawn into fibres.
    Step 5
    → The fibres can be dyed in various colours, as the natural fleece of sheep and goats is black, brown or white.
    Step 6
    → The fibres are straightened, combed and rolled into yarn. 
    → The longer fibres are made into wool for sweaters and the shorter fibres are spun and woven into woollen cloth.
    Silk
    → Silk fibres are also animal fibres. The rearing of silkworms for obtaining silk is called sericulture.
    Life history of silk moth
    → For obtaining silk, silkworms are reared on a large scale. A female silk moth gives hundreds of eggs on the mulberry leaf. 
    → The eggs are then hatched by keeping them under the right temperature and humidity conditions. 
    → Then, the silk caterpillars are fed on mulberry leaves. After 20-25 days, caterpillars stop eating and start spinning cocoons around them.
    → Further development of the moth continues inside the cocoon. The moth leaves the cocoon after its development is complete.

    → Once the moth has left the cocoon, it is collected to obtain silk.

    → The cocoons are kept under the sun or boiled or exposed to steam to separate the silk fibres. This process is known as reeling the silk.

    → Silk fibres obtained after reeling are spun into silk threads.

    From cocoon to silk

    → For obtaining silk, moths are reared and their cocoons are collected to get silk threads.

    Rearing silkworms

    → A female silk moth lays hundreds of eggs at a time.


    → The eggs are stored carefully on strips of cloth or paper and sold to silkworm farmers.

    → The farmers keep eggs under hygienic conditions and under suitable conditions of temperature and humidity.

    → The eggs are warmed to a suitable temperature for the larvae to hatch from eggs.

    → This is done when mulberry trees bear a fresh crop of leaves.


    → The larvae, called caterpillars or silkworms, eat day and night and increase enormously in size.

    → The worms are kept in clean bamboo trays along with freshly chopped mulberry leaves.

    → After 25 to 30 days, the caterpillars stop eating and move to a tiny chamber of bamboo in the tray to spin cocoons.

    → Small racks or twigs may be provided in the trays to which cocoons get attached.

    → The caterpillar or silkworm spins the cocoon inside which develops the silk moth.

    Processing silk

    → A pile of cocoons is used for obtaining silk fibres.

    → The cocoons are kept under the sun or boiled or exposed to steam.

    → The silk fibres separate out. The process of taking out threads from the cocoon for use as silk is called reeling the silk.

    → Reeling is done in special machines, which unwind the threads or fibres of silk from the cocoon.

    → Silk fibres are then spun into silk threads, which are woven into silk cloth by weavers.
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