Fibre to Fabric Class 7 Notes Science

Chapter Notes - 

Clothes are one of our basic needs. Clothes protect us from heat, cold, rain, dust, insects, etc. Clothes also make one civilized and smart. Clothes are made of cloth. Cloth is also known as fabric. Fabric is made of fiber.

Fibers are two types – Natural and Man made.

Natural fibers- Natural fibers are obtained from plants and animals; such as jute, cotton, wool, silk, etc.

Manmade fibers- Fibers that are synthesized in the laboratory are called man made fiber, such as terylene, terry-cotton, acrylic, etc.

Natural fiber: Natural fibers can be classified into two types – Plant fiber and Animal fiber.

Plant Fiber: Fiber obtained from plants is called plant fiber. For example – cotton, jute, flex, etc.

Animal Fiber: Fiber obtained from animals is called animal fiber. For example – wool and silk.

Examples of Natural and Synthetic FibersWOOL-

There are many animals that bear a thick coat of hair on their body. Such animals generally live in cold climates. Thick coat of hair over the body of such animals traps a lot of air and keeps them warm as air is a bad conductor of heat. It prevents the warmth of the body from escaping and also prevents the coldness of the surroundings from entering. Thus, a thick layer of hair over their body protects them from harsh cold. For example: Sheep, Goat, Camel, Yak, etc.

Fleece and Wool bearing animals: Sheep, goat, Camel, Yak, etc. bear two types of hair – coarse hair and fine-soft under hair. Fine soft hair is found close to the skin in such animals. The fine soft under hair is called fleece. Fiber for wool is obtained from the fleece (hair) of such animals and hence such animals are called wool bearing animals.

Many breeds of sheep are found in India. Sheep gives milk and meat; in addition to wool, but are reared mainly to obtain wool in different parts of the world.

Angora wool is obtained from Angora Goats. Angora Goats are found in hilly regions, such as Jammu and Kashmir. Pashmina wool is obtained from Pashmina Goats. Yak wool is obtained commonly in Tibet and Ladakh. Alpaca and Llama are other animals that give wool.

Selective breeding and rearing of sheep: Some breeds of sheep bear only a coat of fine hair. Such animals are reared by selective breeding. Selective breeding is the process to obtain animals or plants having special characteristics.

In India, sheep are reared generally in the states of Jammu and Kashmir, Himachal Pradesh, Uttaranchal, Arunachal Pradesh and Sikkim, or the plains of Haryana, Punjab, Rajasthan and Gujarat.

Food of sheep: Sheep are herbivores and feed generally on grass and leaves. Apart from grass and leaves they also feed on corn and oil cakes. Oil cakes are materials left after obtaining oil from oil seeds.

Process to obtain wool from sheep: Steps given below are followed to obtain wool from sheep or other wool bearing animals:

Step 1 – Shearing - The fleece (hair) of sheep is shaved off along with a thin layer of skin. In olden days this was done using a pair of metal blades. But now-a-days machines are used to cut off the fleece. This is similar to shaving of beards or hair. This process is called shearing.

Shearing is done generally in summer so that sheep could get new hair by winter to get protection against cold.

Step -2 – Scouring – Fleece, after shearing, is washed properly to remove dirt and grease. The washing of fleece; after shearing; is called scouring.

Step- 3 – Sorting – After scouring, fleece are sorted according to texture. This process is called sorting.

Step – 4 – After sorting, fluffy fibers; called burr; are picked out from the hair. Burr is the fiber that gives wool.

Step 5 – Dying – After sorting and picking out of burrs, these are dyed in desired colors.

Step 6 – Spinning – The fibers are then straightened, combed and rolled into yarns.

Wool yarn is used in knitting sweaters and woolen cloths, i.e. fabric.

SILK

Silk is another important animal fiber. Silk worm spins silk. Silkworm is reared to obtain silk.

History of Silk:

Silk was discovered in China; around 3500 BC. Silk became a prized possession because of its fine quality and luster. Originally, it was used by emperors only. It was through trade that silk spread to other parts of the world over a period of time. Silk was a staple item of trade during ancient times. Due to this, the ancient trade routes which linked China to other parts of the world are called ‘Silk Route’.

As per historians, silk was produced in India also. Proof of use of silk during the Indus Valley Civilization has also been found.

Types of Silk: Different types of silkworm produce different types of silk; in terms of luster and texture. For example; tussar silk, muga silk, kosa silk, etc. are produced by different types of silk moths. Mulberry silk is the most common silk moth.

Rearing of silkworm: Rearing of silkworm is known as SERICULTURE. Silkworms are reared on mulberry leaves as they feed on mulberry leaves.

Life cycle of silkworm:

Female silk moth → Lays eggs → After about 14 days eggs are hatched into larva →Grown into Pupa → Weave a net and enclosed itself → Produce liquid protein from its salivary glands moving it’s head in the shape of ‘8’ forming cocoon→ Live in the cocoon for some time → After coming out of cocoon grows into silk moth.

Silk moth to silk:

After they are laid by the silk moth; eggs are stored over a clean cloth or paper strips. When larvae are hatched from eggs, they are kept in clean bamboo trays with fresh leaves of mulberry. Larvae feed on mulberry leaves for about 20 to 25 days. After that, larvae move into tiny chambers of bamboo in which they start spinning cocoons. They do it by secreting liquid protein from their salivary glands. Finally they enclose themselves in a cocoon. Cocoons get hardened because of exposure to air.

Obtaining of silk from cocoon:

First of all, cocoons are boiled and then silk fiber is separated out; using machines. Machine unwinds the silk thread from cocoons. The process by which silk fiber is obtained is called REELING THE SILK.

Silk thread so obtained is woven into different types of cloths, i.e. fiber.