July 18, 2009

The Queen of Fibers

I love silk. I love sewing with it, I love touching it, I love wearing it... If I could, I would make all of my bedsheets out of silk and sleep on it. This fascination made me curious about how silk is produced. What follows, is the research I did back in high school about silkworms. It was a presentation I gave orally, and since I've lost my original pictures, these are ones I found on the Internet.

Silk is often referred to as the queen of all fibers. It has been used throughout history to clothe nobility, and was a staple during the era of trade. The discovery of silk was made over 5000 years ago, in China. According to Chinese legend, a princess was out in her garden when the cocoon from a silkworm fell into her tea. The princess was surprised by the thread coming from the cocoon and started pulling, until the cocoon unraveled completely. She then took this extremely fine, but strong thread, and began to weave with it. Such treasured fabric coming from an insect no bigger than a man's finger deserves a closer look. Today I will examine this small creature, how silk is manufactured today, and what its uses are.

The silkworm is not technically a worm; it is the larvae caterpillar of a moth, the scientific name being bombyx mori. There are two main types of silkworms: wild ones and domesticated ones. The main difference between the two is the strength of silk they produce. Wild silkworms produce a low quality of silk, weak and full of "slubs", a word used to describe irregularities in the thread. Domesticated silkworms produce a very high quality silk. Today, they are entirely dependent on humans for reproduction and can not survive in the wild. When the silkworm eggs are first hatched, the larvae is smaller than a grain of rice, but it begins to eat day and night, growing to about two and three-quarters of an inch long. A silkworm's diet consists wholly of mulberry leaves. Each year over 10 billion pounds of leaves are consumed by silkworms worldwide! The young caterpillars molt four times shedding their outer exoskeleton. They then spend 36 hours spinning themselves a cocoon out of raw silk produced in their salivary glands. The cocoon is about one inch long and is yellow in color. This serves to protect the worms during the pupa stage where they transform from a caterpillar to a moth.

The process of harvesting silk has not changed much since its development. In the wild, silk worms remain in their cocoons for three weeks, then they eat through the cocoon and emerge as a white hairy moth. This damages the silk of the cocoon, which is why wild silk is a lower quality. On silk farms, where domestic worms are raised, a small amount of moths are allowed to emerge and reproduce, but the rest are baked to kill the pupa inside. Next, the cocoons are placed in hot water which loosens the gum holding the cocoon together, and the silk is unwound onto large reels. A silkworm's cocoon is made from one single silk thread that is over a mile long, and 1/2500th of an inch in diameter. Ten of these single threads are wound together to form one strong thread that is then used for weaving. It takes over 2000 cocoons to make one pound of silk, and 70 million pounds are produced yearly. Because the process of harvesting domestic silk kills the larvae, silk farmers have come under criticism from animal rights activists. They complain that too many silk worms are killed, and believe that, since artificial silks are available, they should be used instead. In many countries, however, the larvae are not killed unnecessarily, they are cooked and served as a delicacy! The process of harvesting silk is really quite uncomplicated and, though there are silk farms from which to obtain commercial silk, many crafters like to process it in their own home in order to have unique silk for their projects.

The strong and beautiful silk fiber is a triangular prism like structure, which refracts incoming light at different angles; this is what causes silk's shimmering appearance. Silk is an extremely versatile fabric. It is warm in winter and cool in summer. In Japan, silk from 2100 cocoons is used to make one kimono, a traditional Japanese garment. Similarly in India, silk is widely used in the traditional sari. In addition to clothing, silk is used in parachutes, bicycle tires, comforter filling, and artillery gunpowder bags. In ancient times, Mongols used silk as a type of under-armor. Silk was very strong, and its benefit to the soldier was that it stopped arrow penetration. By wearing a silk undergarment the arrow would barely enter into the body, allowing it to be pulled out by tugging on the unbroken silk. Thus there was no contact between the arrowhead and the body. This greatly reduced the number of infected wounds. So you can see, silk is not only prized for it's beauty, but for its functionality as well.
Silk is an amazing fiber used all over the world. 5000 years ago when the Chinese first developed the process of making silk, they tried very hard to keep it a secret from the rest of the world. It did not remain clandestine for long. One legend has it that a Chinese princess smuggled silkworm eggs to Japan by hiding them in her hair! Today Japan is the largest producer of silk in the world, followed by Thailand. Because of their warm climates silk can be produced almost year round. By looking at the life of a silk worm, the process of harvesting silk, and its uses throughout history, we can see why silk is called the queen of fibers.

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