Silk production
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A moth lays 500 or so eggs and then dies
Baby worms hatch from the eggs are fed mulberry leaves for one month until they are fat
The worms spin cocoons
The cocoons are steamed to kill the growing moth inside
The cocoons are rinsed in hot water to loosen the threads
Women would unwind the cocoons and then combine six or so fibers into silk threads
The threads are woven into cloth
The cloth is then pounded to make it softer
Why it was valuable to the Chinese
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Silk cloth was extremely valuable in Ancient China. Wearing silk was an important status symbol. At first, only members of the royal family were allowed to wear silk. Later, silk clothing was restricted to only the noble class. Merchants and peasants were not allowed to wear silk. Silk was even used as money during some Ancient Chinese dynasties.
Why it was secret
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Silk became a prized export for the Chinese. Nobles and kings of foreign lands desired silk and would pay high prices for the cloth. The emperors of China wanted to keep the process for making silk a secret. Anyone caught telling the secret or taking silkworms out of China was put to death.
Hope all this helps :)