NCERT 7th Class (CBSE) Science: Fibre to Fabric

Question: Define Shearing and Scouring.

Answer: Shearing: The process of removal of the woolen coat or fleece from an animal is called shearing.

Scouring: The process of removing dirt, dust and grease from the sheared hair is called scouring.

Question: Explain the process to obtain silk thread from cocoon.

Answer: Cocoons of silk moth are used to obtain the silk fibres. These cocoons are kept under the sun or boiled or exposed to steam. The silk fibres is then separated. This process of obtaining wool from the cocoons is called reeling the silk. Reeling is done in special machines.

Question: How silk fibres of different textures are prepared?

Answer: The silk yarn is obtained from the cocoon of the silk moth. There is a variety of silk moths which look very different from one another and the silk yarn they yield is different in texture like coarse, smooth and shiny. Thus tassar silk, mooga silk and kosa silk are obtained from cocoons spun by different types of moths. The most common silk moth is the mulberry silk moth.

Question: What treatment is given to the sheared hair of the sheep in Scouring, Sorting and Carding?

Answer: Scouring: In scouring, the sheared skin with hair is thoroughly washed in soap solution in a number of tanks to remove grease, dirt and dust.

Sorting: In sorting the dried hair of different textures are sorted out. The small fluffy fibres called burrs are picked out and sent for reprocessing.

Carding: In carding process, selected curly wool fibres are straightened by passing through rollers.