Page 33 - Ripples SCIENCE 7 - TEJPUR Edition 2024 Answer Key

wetting agents, alkali etc. After the scouring process, materials become ready for the

next bleaching process. For this, it is passed through a series of rollers and dryers.
Step 3: Sorting– After scouring, because of the chemical treatment, some wool gets

damaged, the damaged wool is carefully removed. The hairy skin is sent to factories
where hair of different textures are separated. This process is known as sorting. The

woollen fibres are sorted according to the quality, such as fine, coarse, long, short
etc. The same quality obtained from a large number of sheep are then mixed together.

Step 4: Removing burr– You might have seen soft
fluffy fibres that appear on your sweater. These are

called burrs. These burrs are picked out from the hair
that has been scoured. After removing burrs, the

fibres are again scoured and then dried.
Step 5: Dyeing– We see woollen clothes in a variety

of colours. However, the natural colours of the fleece
of sheep are white, brown and black. Fibres are dyed in different colours and then

dried to get a variety of coloured fibres.
Step 6: Making yarn– After the dyeing process, the fibres are straightened, combed

and rolled into thick yarns called wool. After spinning, the wool is either woven or
knitted to make garments.

3. How is silk processed? Explain in detail.
Ans. Rearing : Silk moths produce hundreds of eggs at a time. Silk farmers collect these

eggs and store them in an environment with an appropriate temperature, humidity
and hygienic conditions. In order to hatch the larvae out of the eggs, the eggs are

placed in frames and kept in an incubator. After about 20 days, these frames are
taken out of the incubator. Till then, most eggs hatch into larvae. These hatched

larvae are called silkworms.
The silk farmers spread fresh mulberry leaves on these frames each day for the

silkworms to feed on. This is generally done at the time when fresh leaves appear
on the mulberry trees so that the silkworms have enough to feed on. The silkworm

continues to feed day and night for 4–6 weeks and grow in size considerably. They are
then placed into individual chambers in bamboo trays, where they begin to produce

silk thread and eventually form a protective cocoon around themselves.
Processing of silk : The cocoons are collected and are either kept under the sun or

boiled so that the silk fibres can be separated. The next step involves taking out
silk fibres by unwinding the threads from the cocoon. This process is called reeling,

which is done in silk factories by machines and even by hand.

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