Fibre to Fabric

NCERT CLASS 7 Science Chapter 3- FIBRE TO FABRIC
• Fibres are obtained from both plants and animals. Here we talk about two fibres obtained from animals- Wool and Silk.
• Wool is obtained from the fleece (hair) of sheep or yak.
• Silk fibres come from cocoons of the silk moth.

WOOL
• Wool-yielding animals like sheep, goat, and yak bear a thick coat of hair on their body which traps a lot of air. As air is a poor conductor of heat, so, hair keeps themwarm. Wool is derived from these hairy fibres.
• The hairy skin of the sheep has two types of fibres that form its fleece:

1. the coarse beard hair, and
2. the fine soft under-hair close to the skin.
• The fine hair provides the fibres for making wool.
• Selective breeding is the process of selecting parents for obtaining special characters in their offspring, such as soft under hair in sheep.
• Yak wool is common in Tibet and Ladakh.
• Mohair is obtained from angora goats, found in hilly regions such as Jammu and Kashmir.
• Wool, obtained from Kashmiri goat hair is soft and is woven into fine Pashmina shawls
• The fur (hair) on the body of camels is also used as wool.

• Llama and Alpaca, found in South America, also yield wool.

SOME INDIAN BREEDS OF SHEEP

NAME OF BREED

QUALITY OF WOOL

STATE WHERE FOUND

Lohi

Good quality wool

Rajasthan, Punjab

Rampur Bushair

Brown fleece

Uttar Pradesh, HimachalPradesh

Nali

Carpet wool

Rajasthan, Haryana, Punjab

Bakharwal

For woollen shawls

Jammu and Kashmir

Marwari

Coarse wool

Gujarat

Patanwadi

For hosiery

Gujarat

PROCESSING FIBRES INTO WOOL

For obtaining wool, sheep are reared and their hair is cut and processed into wool.

The processing of fibre into wool can be represented as follows:

Shearing → Scouring → Sorting → Cleaning of burrs → Dyeing → Rolling

 

  STEP I

• The fleece of the sheep along with a thin layer of skin is removed from its body. This process is called shearing.
• Usually, shearing is done during the hot weather to helpsheep survive without their protective coat of hair. The hair provides woollen fibres which are then processed to obtain woollen yarn.

 

STEP II

• In a process called scouring, the sheared skin with hair is thoroughly washed using machines to remove grease, dust and dirt.

 

STEP III

• Sorting is done in which the hair of different textures areseparated or sorted.
• But a sorter’s job is risky as sometimes they get infected by a bacterium, anthrax, which causes a fatal blood disease called sorter’s disease. Such risks faced by workers in any industry are called occupational hazards.

 STEP IV

• The small fluffy fibres, called burrs, are picked out from the hair. These are the same burrs which sometimes appear on sweaters.

• The fibres are scoured again and dried. This is the wool ready to be drawn into fibres.

    STEP V

• The fibres can be dyed in various colours, as the natural fleece of sheep and goats is black, brown or white.

     STEP VI

• 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
• The rearing of silkworms for obtaining silk is called sericulture.
• The female silk moth lays eggs, from which hatch larvae called caterpillars or silkworms.
• They grow in size and when the caterpillar is ready to enter the next stage of its life, called pupa, it first weaves a net to hold itself.
• Then it swings its head from side to side in the form of the figure of eight (8).
• During these movements of the head, the caterpillar secretes fibre made of a protein which hardens on exposure to air and becomes silk fibre.
• Soon the caterpillar completely covers itself by silk fibres and turns into pupa. This covering is known as cocoon.
• The further development of the pupa into moth continues inside the cocoon.
• Silk fibres are used for weaving silk cloth. The soft silk yarn is as strong as a comparable thread of steel.
• The silk yarn (thread) is obtained from the cocoon of the silk moth. There is a variety of silk moths and the silk yarn they yield is different in texture. Thus, tassar silk, mooga silk, kosa silk, etc., are obtained from cocoons spun by different types of moths.
• The most common silk moth is the mulberry silk moth. The silk fibre so obtained is soft, lustrous and elastic and can be dyed in beautiful colours.

FROM COCOON TO SILK
• Silk moths are reared and their cocoons are collected to get silk threads.
• 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 and suitable conditions of temperature and humidity 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. They 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.
• 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. This 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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