Sunday, November 3, 2013

Vacaton Destination - China Part 2

Vacation China – Silk, Part 2- Production

Silk is a filament secreted by  the silkworm when spinning its cocoon, and the name for the threads, yarns and fabrics named from the filament.  Most commercial silk is produced by the cultivated silkworm, Bombyx mori. 

Its Origin, Culture and Manufacture
The Nonotuck Silk Company
Florence Massachusetts

The secret of silk production was a closely guarded Chinese secret.  The penalty of revealing this secret was punishment by death. Inevitably, the secret was too valuable and there are several versions in folklore, which describe the lengths smugglers would go to steal the secret from China to sell it to the West  One tells of monks hiding cocoons in their walking sticks!!

Bombyx mori feeds exclusively on the leaves of various mulberry trees and spins a thin, white filament.  There are several varities of wild silkworms which feed on oak, cherry and mulberry leaves, but their filament is brown and coarse and 3 times the thickness of the cultivated.

Teaching sample of trays used for feeding.  In factories the worms are raised on huge trays fitted with a wire bottom for cleaning of the larvae waste.  The wire is then covered with fresh mulberry leaves

Carefully selected moths lay 500-700 eggs apiece.  One ounce of silkworms requires nine tons of mulberry leaves to reach maturity, their cocoons will produce 12  pounds of silk.
Eggs take 14 days to mature into larvae.  The larvae are raised on trays kept in a temperature-controlled, clean  environment and are fed every 2-3 hours. Fully grown in approximately 5 weeks, they are 70 times their original size.  Their rear silk glands produce an animal protein called fibron which is activated and sent to silk producing glands.  The silkworms are placed on a bed and enter the pupa stage, enclosing themselves in a silk filament in an endless series of figure-eights (300,000 times) 1 ½ miles in length.

Eight to nine days the silkworm changes into a moth and must emerge from the cocoon.  To do so it produces an enzyme to soften the cocoon and produce a hole, from which it emerges.  Since the enzyme is destructive to silk fibers , the fibers break down from their mile-long filament into shorter  segments of random length, ruining the silk threads.  (These waste cocoons are used to spin noil, to make various products but are not suitable for fine silk thread production.)  To prevent this, at the factory the cocoons are gassed, boiled or steamed, killing the silkworm.  Of course, enough moths are allowed to hatch so that egg-laying can continue,

Moths emerging from cocoons
Note the damage to cocoons

Intact cocoons.  Dead pupa taken from cocoons prior to reeling.  Fear not, these are an excellent source of protein and are use in the cosmetic industry. 

After drying the cocoon are inspected and graded and sent to a filature (factory) for reeling..Today, automated reeling machines are equipped with sensors, allowing for immediate replacement of empty cocoons or broken filaments. The silk filament is made stronger for weaving by plying, called throwing,  increasing the twist or adding more strands together.  

Moi inspecting a n automated reeling and plying machine at the factory.  The cocoons are stored in the blue containers at the bottom of the reeler.  The plied silk thread is on the spools at the top

Skeins of silk are formed into bundles (29) and collected into bales (132#), the amount raw silk is traded for export.

Vintage photo of silk traders examining skeins of silk

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