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The Silk Thread

Cocoons are sorted according to color and texture. For reeling, the unpierced cocoons that are stifled by heat are used. Cocoons are soaked in a basin of water at 140° F to soften the silk gum, or sericin. Filaments from several cocoons are grouped together. Fibers are threaded through a small hole or eye in the reeling frame and then are twisted with several fibers and threaded through another eye. Further twisting occurs when the yarns are wound, or reeled. But the filaments adhere together because of the natural gum secreted by the silkworm. In this condition the thread is too thin and weak to be used without further twisting - called throwing. Sometimes single strands of thread are doubled and twisted. For example, yarns to be used for lengthwise or warp yarns of a fabric must be very strong to withstand the strain of wear. Accordingly a silk warp yarn is made of several single yarns twisted (with a left-hand twist) to the right. Twisting increases the strength of a yarn. Yarns made of reeled-silk threads twisted together are called thrown silk.


Each woman works at a copper bowl of hot water, into which cocoons are plunged. Several sharp dabs with a brushwood brush loosen the coarse outer covering. Then the tiny strands of silk are reeled off, passing through glass guides on their way to the reels in the background and in the process of being twisted with from 2 to 6 other strands. These yarns are wound on spools or in skeins, ready for the weavers. To facilitate handling, oils may be added to the gum weight by the throwster.

Before silk can be reeled from the cocoon, long, tangled ends must be removed so that an end can be found with which to start the reeling process. The tangled ends are put aside because they cannot be reeled. Likewise, when most of the fiber has been reeled from a cocoon, there may be short lengths. These short pieces are laid aside also. Only about half of the silk of a cocoon is fit to be reeled. The rest is used in inferior silk cloth.

When yarns are prepared for weaving, the skeins of yarn are boiled in a soap solution to remove the natural silk gum or sericin. The silk may lose from 20 to 30 per cent of its original weight as a result of boiling. As silk has a great affinity for metallic salts such as those of tin and iron, the loss of weight is replaced through the absorption of metals. Tannin may also be used as a weighting material. Thus, a heavier fabric can be made at a lower price than that of pure silk. Heavily weighted silk may not wear as long as pure unweighted silk, because sunlight and perspiration weaken or destroy the fibers. Furthermore, heavy weighting causes silk to crack. The long treatment of silk in the weighting process may also have a weakening effect on the fibers. Silk containing no metallic weighting is called "pure silk."

The Silkworm

Published on Saturday, 07 October 2006 18:00

Silk WormSilkworm 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) .

 

EggWormSilk Worm 30 Days

Worm Cocon4 Month5 month old

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.

 

 

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