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 Silkworm Silk is an animal fiber. It is the product of the silkworm, of which there are two varieties: the wild and the cultivated. The fibers of the wild silkworm are brown, instead of yellow to gray, and have a coarse, hard texture. This worm feeds on the scrub oak instead of the mulberry leaf and grows in India, China, and Japan. Fibers from the first two countries are called tussah silk, and in Japan they are called wild silk. Tussah silk is used in such fabrics as shantung, pongee, and shiki.
The cultivated silkworm requires a great deal of care. Quiet and sanitation are necessary. A silkworm farmer treats them as royalty to the extent of turning his house over to them in the feeding season; for when his attic floor becomes covered with mulberry leaves, each with it's hungry worm, he carpets the rooms downstairs with more leaves and sleeps on the roof.
A whole scientific industry, that of raising mulberry trees for food for the worms, has grown up. The best mulberry leaves seem to come from plants that are the result of a combination of the tall mulberry tree called the dwarf or shrub mulberry tree. Silkworms live a very short time - only about two months. During that period they pass through four stages of development: (1) egg, (2 & 3) worm , (4) chrysalis (cocoon), and (5 & 6) moth (mulberryspinner). Eggs which have been kept in cold storage for approximately six weeks after they were laid are bathed in warm water and dried in the air. Then they are placed in incubators, where they remain until all are hatched (about thirty days) .
A tiny white worm about 1/4 of an inch long is hatched from each egg. These worms are very delicate and require the utmost care. They are placed on bamboo trays covered with straw mats on which selected mulberry leaves are laid. The worms are very greedy; it is estimated that each worm eats about 30,000 times its initial weight. During this stage the silkworm molts (sheds his skin) four-times. At the end of about thirty days the worm ceases to eat, attaches itself to a piece of straw, and begins to spin its cocoon.
Fine gummy filaments exude from two openings under the worm's mouth. The filaments are hardened when exposed to air. Sericin, or silk gum, exudes from the apertures, and this gum causes fibers to adhere to one another. The worm covers itself with these filaments, and when the cocoon is completed, in about three days, it sleeps for fifteen to twenty days. One manufacturer estimates that 2,500 to 3,000 cocoons are necessary to make one yard of silk fabric.
If the moth is permitted to emerge from the cocoon, the silk filament is broken into many short pieces. Therefore, the chrysalis (unless it is selected for breeding) is suffocated while it is still inside the cocoon. Long thin fibers can be reeled from the unpierced cocoons. The moths which emerge from cocoons reserved for breeding purposes are creamy white. Three days after they have hatched, they mate, lay eggs, and die. Their cycle of life is complete. |
Silk - The Material
