Why do we need to boil the cocoons for extraction of silk class 7th?

To obtain the silk, cocoons are treated with boiling water to kill the living pupa inside. Thread is recovered from the killed cocoons and this process is known as reeling . hope this helps you! !

Why do cocoons boil to get silk?

During boiling, some amount of water enters the cocoon cavity and makes it soft. This helps in separating the fibres from cocoon during the reeling process. … Due to hot water, pupa dies and does not emerge out of cocoon.

Why silkworm cocoons are boiled or steamed before silk extraction?

Answer: Cocoons are Placed in boiling water to get smooth & continious thread from it. … The cocoons are put on steam (Hot boiling water Vapours) to soften the Cocoons Upper Layers and Kill the larvae (Silk Worm) & can be stored as is for more than 10 days. Now the Cocoon is ready to manufacture Raw Silk.

Why is it necessary to boil or bake the cocoons of Silkmoth?

It is necessary to boil or bake the cocoon because by this the larva which converted into cocoon will die and only it’s silkshell remains. Also, by this process the silk get a little bit unwind and easy to process further.

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Why are the cocoons boiled in hot water or treated in ovens Class 7?

Cocoons are boiled in hot water or treated in ovens so as to get the silk. Boiling with hot water or treating in ovens results in softening of the upper layer of of the cocoon or killing the pupa inside.

Why are silk cocoons boiled give two reasons?

To get the silk from the cocoons at the optimum time, before the worm makes a hole in the cocoon reducing it’s value, they are placed in boiling water to kill the worm and make it easier to unwrap the silk threads.

How are cocoons boiled?

Cocoons are put into a pan of boiling water. The groping ends of the cooked cocoon can be completed with the stirring rod in the pan (see Appendix, Figure 14). The cocoons contained in the wire cage are placed into the boiling water and then boiled for a few minutes.

What will happen if cocoon is boiled?

Answer : It is important to boil cocoons to obtain silk fibers. After boiling, the silk fibers easily separate and we get long continuous silk thread. … If cocoon is not boiled, the fibres obtained will be brittle, and we will get fragments of the thread instead of a long continuous silk thread.

Why are cocoons kept under direct sun or in boiling water?

Cocoons are kept under the Sun and exposed to steam. The warmth causes the silk fibres to separate from the rest of the cocoon. It allows us to get soft and continuous silk thread from cocoons and the same cannot be obtained from treating in cold water.

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How many types of silk are there name them?

In short, there are four types of natural silk produced around the world: Mulberry silk, Eri silk, Tasar silk and Muga silk.