Why Silk Not Good ¤¤¤å

Silkworm is a common name for the silk-producing larvae of any of several species of moths. The larvae is not really a worm at all but a caterpillar. There are several species of silkworm that are used in commercial silk production, however, Bombyx mori is the most common.

Silk is used for suits, coats, trousers, jackets, shirts, ties, lingerie, hosiery, gloves, lace, curtains, linings and handbags. Synthetic fibres such as nylon and polyester are stronger than silk and lower in price. In common with western factory farming techiques, the main areas of silk production are labour-intensive, automated and soul-less. The terminology - stifled for killed and crop for pupae - echoes the denial that we are dealing with living creatures which are awe inspiring when one considers their metamorphic life-cycle. Plant fibres are capable of producing some amazing fabrics. Fibres from the pineapple, for example, may be made into fabrics as silky as any silk. Synthetic fibres e.g. nylon produced from minerals, polyester from petroleum spirit (Terylene, Dacron) or acrylic from oil and coal (Courtelle, Orlon, Dralon) also have their place.

Another product, now almost entirely replaced by nylon, was silkworm gut. Immediately before the cocoon stage, pupae were killed by immersion in an acid bath. Their bodies were opened and the thread which was intended to build the cocoon, was removed from their silk glands. This 'gut' was once favoured by surgeons for stitching and by anglers for lines.

Silkworms possess a pair of specially modified salivary glands called silk glands or sericteries which are used for the production of silk cocoons. These glands secrete a clear, viscous, proteinous fluid that is forced through openings called spinnerets on the mouthpart of the larva. As the fluid comes into contact with the air it hardens. The diameter of the spinneret determines the thickness of the silk thread.

Silk from the Thai moth is hand reeled from green cocoons. These are cocoons that still contain the live pupae. These small cocoons do not have the pupae 'stifled' or killed before the thread is unwound as it would make it difficult to reel. The green cocoons are placed in hot, nearly boiling water, which loosens the end of the thread. With less than 10 days available before the moths emerge and ruin the cocoon, the Thai workers may run out of time limiting the scale of the industry. Even experienced workers rarely produce more than 300kg/day. The emerging pupae may be eaten by local workers.

After it has reached its maximum growth at 7.5cm at around 4-6 weeks it stops eating, changes colour and attaches itself to a compartmented frame, twig, tree or shrub in rearing houses to spin their silk cocoons over a 3-8 day period. This is period is termed pupating.
Steadily over the next four days the silkworm produces a fine thread by making a figure of eight movement some 300,000 times, constructing a cocoon in which it intends to spend the chrysalis stage where it is in a state of sleep and casting off of skin. After this the pupae begins the sixteen days which would normally result in the miracle of transformation to a winged being - the moth. However, if the pupae (chrysalis) remains alive it will begin to secrete an alkali which eats its way through the cocoon ruining the silk threads. So, as the cocoons are completed the pupae are killed or 'stifled'.

Tearing during emergence damages the silken cocoon beyond use commercially. Therefore during the production of silk, only enough adult moths are allowed to emerge to ensure continuation of the species. Most of the remainder of the silkworms are killed by heat, e.g. immersion in boiling water, steaming, drying an oven, by laying in the hot sun for a day, electrocution or subjection to microwaves.

The adult moths retained for reproduction purposes are too fat to fly as the best fliers do not produce as much silk. The stifled or dead pupae are usually composted to feed the mulberry trees.

The silk is a continous filament fibre consisting of fibroin protein secreted from two salivary glands in the head of each larvae and a gum called sericin which cements the two filaments together. Silk must be reeled off the cocoon quickly before the pupae begin to rot and taint the thread with unpleasant smells. Cocoons are then softened in hot water to remove the sericin which frees the silk filament ends for reeling or filature. Single filaments are drawn from cocoons in water bowls and combined to form yarn. This yarn is drawn under tension through several guides and eventually wound onto reels. The yarn is dried, packed according to quality and is now raw silk ready for marketing. The worn and withered body of what was intended to become the wondrous flying creature slips silently away.

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World silk production has roughly doubled during the last 30 years in spite of the availability of man-made fibres. China and Japan have been the main silk producers, together manufacturing more than half of the world production each year. Chinese silk is highly prized throughout the world. Since 1949 silk making methods have been modernized and silk is of better quality. World silk production in 1940 was 59 million kg. By 1950 it had dropped to 19 million kg. By the mid-1980s it had climbed to about 68 million kg.

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For more detailed information on silk, please visit The Vegan Society