Chapter 3 Class 7 Science JKBOSE NCERT Book Notes FIBRE TO FABRIC
Notes for Class 7th Science Chapter 3 Fibre to Fabric
Animal Fibres- Wool And Silk
Wool
Animals such as sheep, yak, and goats yield wool. These animals have a thick coat of hair on their bodies to keep them warm. Wool is derived from these hairy fibres.
The hairy skin of sheep has two types of fibres (i) Coarse hair (ii) Fine soft hair. The fine soft hair provides fibres for making wool.
Some breeds of sheep possess only fine soft hair. Their parents are specially selected to give birth to such breeds. This process of choosing parents is called selective breeding.
Several breeds of sheep are found in different parts of the country. However, sheep are not the only animals that produce wool. Wool most common in Ladakh and Tibet is Yak wool. Angora wool is obtained from angora goats found in Jammu and Kashmir. The under-hair of the Kashmiri goat is very soft and it is woven into fine shawls called Pashmina Shawls.
The hair found on the body of camels is also used as wool.
Llama and Alpaca, found in South America also yield wool.
Processing of Fibres into Wool
Step I
The fleece of sheep along with a thin layer of skin is shaved off from the body of the sheep. This is called Shearing.
Step II
The removed hairs are washed to remove grease and dust. This is called Scouring.
Step III
The hairs of different textures are separated or sorted. This process is called Sorting.
Step IV
The small fluffy fibres, called burrs are picked out from the hair. The fibres are washed again and dried.
Step V
The fibres are now dyed in various colours.
Step VI
The fibres are straightened, combed and drawn into yarns. The yarns are now ready for making different woollen products.
Silk
Silk fibres are also animal fibres as they are obtained from silkworms.
Sericulture:- The rearing of silkworms for obtaining silk is called sericulture
Life History of Silk Worm
The female silk moth lays eggs from which hatch Larvae. larvae are also called Caterpillars.
They grow in size and when the caterpillar is ready to enter the next stage of life cycle Pupa, it weaves a net to hold itself.
It swings its head from side to side in the form of a figure of 8. During these movements of the head, the caterpillar secretes a protein that hardens on exposure to air. This is the silk fibre.
The caterpillar soon covers itself with silk fibres and becomes a pupa. This covering of fibres is called Cocoon.
Further development of pupa into silk moth continues inside the cocoon
The silk fibres are used to weave silk clothes. The silk yarn is obtained from the cocoon.
There are different types of silk depending upon their texture.
Some important types of silk are tassar silk, mooga silk and kosa silk etc. These are spun by the different types of silk moths.
The most common silk moth is the mulberry silk moth.
India produces 16 per cent of the silk of world. Karnataka is the leading producer of silk followed by West Bengal and Bihar.
Processing of the Silk
The cocoons are dried under the sun or boiled or exposed to steam. This separates silk fibres. This process is called the Reeling of the silk.
Silk fibres are then spun into silk threads which can be used by wavers to weave silk clothes.
