The secret to silk production is the tiny creature known as the silkworm, which is the caterpillar of the silk moth Bombyx mori.
It feeds solely on the leaves of mulberry trees. Only one other species of moth, the Antheraea mylitta, also produces silk fiber. This is a wild creature, and its silk filament is about three times heavier than that of the cultivated silkworm. Its coarser fiber is called tussah.
The life cycle of the Bombyx mori begins with eggs laid by the adult moth. The larvae emerge from the eggs and feed on mulberry leaves. In the larval stage, the Bombyx is the caterpillar known as the silkworm.
The silkworm spins a protective cocoon around itself so it can safely transform into a chrysalis. In nature, the chrysalis breaks through the cocoon and emerges as a moth. The moths mate and the female lays 300 to 400 eggs. A few days after emerging from the cocoon, the moths die and the life cycle continues.
The cultivation of silkworms for the purpose of producing silk is called sericulture.
Over the centuries, sericulture has been developed and refined to a precise science. Sericulture involves raising healthy eggs through the chrysalis stage when the worm is encased in its silky cocoon. The chrysalis inside is destroyed before it can break out of the cocoon so that the precious silk filament remains intact. The healthiest moths are selected for breeding, and they are allowed to reach maturity, mate, and produce more eggs.
Generally, one cocoon produces between 1,000 and 2,000 feet of silk filament, made essentially of two elements. The fiber, called fibroin, makes up between 75 and 90%, and sericin, the gum secreted by the caterpillar to glue the fiber into a cocoon, comprises about 10-25% of silk. Other elements include fats, salts, and wax.
To make one yard of silk material, about 3,000 cocoons are used. Animal fibre produced by certain insects as building material for cocoons and webs. In commercial use it refers almost entirely to filament from cocoons produced by the caterpillars of several moth species of the genus Bombyx, commonly called silkworms. Silk is a continuous filament around each cocoon. It is freed by softening the cocoon in water and then locating the filament end; the filaments from several cocoons are unwound at the same time, sometimes with a slight twist, to form a single strand. In the process called throwing, several very thin strands are twisted together to make thicker, stronger yarn.
Silk is made up of the amino acids Gly-Ser-Gly-Ala and forms Beta pleated sheets. H-bonds form between chains, and side chains form above and below the plane of the H-bond network. The high proportion (50%) of glycine, which is a small amino acid, allows tight packing and the fibers are strong and resistant to stretching.
The tensile strength is due to the many interseeded hydrogen bonds. Since the protein forms a Beta sheet, when stretched the force is applied to these strong bonds and they do not break. Silk is resistant to most mineral acids, except for sulfuric acid, which dissolves it. It is yellowed by perspiration.
Wild-silks are silks derived from silkworms that are "untamed", grown in the wild or in the forests. Different types of silkworm (factoring in their diet and habitat) make different types of silks.
Wild silk, while coarser than commercial silk, is lightweight and naturally comes in a variety of shades.
Silks like muga, tussar and eri make lovely scarves, shawls and clothing that boast of unique natural textures and patterns.
These silks are most often dyed by natural pigments extracted from fruits, vegetables and flowers.
In addition, silk is biodegradable as well! By enjoying silk, wild silk in particular, you help thousands local farmers and woman artisans. Silk production remains a major source of economic independence in areas where wages are low and poverty is the norm.
Your purchase allows retailers like us and fair trade organizations to ensure that the working conditions, medical health and treatment of silk workers are fair, beneficial and accessible.
In the end, it is not only retailers like us and consumers like you who get to enjoy the many benefits of silk, but people like Preeti and her tribe can derive a great deal of life-giving financial security, self-respect and empowerment from this simple but elegant fabric. (Different Types of Silk is an Excerpt from Article - AHIMSA )
Cocoon Silk moths lay eggs on specially prepared paper. The eggs hatch and the caterpillars (silkworms) are fed fresh mulberry leaves. After about 35 days and 4 moltings, the caterpillars are 10,000 times heavier than when hatched and are ready to begin spinning a cocoon.
A straw frame is placed over the tray of caterpillars, and each caterpillar begins spinning a cocoon by moving its head in a "figure 8" pattern. Two glands produce liquid silk and force it through openings in the head called spinnerets. Liquid silk is coated in sericin, a water-soluble protective gum, and solidifies on contact with the air.
Within 2–3 days, the caterpillar spins about 1 mile of filament and is completely encased in a cocoon. The silk farmers then kill most caterpillars by heat, leaving some to metamorphose into moths to breed the next generation of caterpillars.
Harvested cocoons are then soaked in boiling water to soften the sericin holding the silk fibers together in a cocoon shape. The fibers are then unwound to produce a continuous thread.
Since a single thread is too fine and fragile for commercial use, anywhere from three to ten strands are spun together to form a single thread of silk.[19] Retrieved October 17, 2010 from http://www.wikipedia.org/wiki/Silk
As the process of harvesting the silk from the cocoon kills the larvae, sericulture has been criticized in the early 21st century by animal rights activists, especially since artificial silks are available.[20] Mohandas Gandhi was also critical of silk production based on the Ahimsa philosophy "not to hurt any living thing." This led to Gandhi's promotion of cotton spinning machines, an example of which can be seen at the Gandhi Institute. He also promoted Ahimsa silk, wild silk made from the cocoons of wild and semi-wild silk moths.[21] Ahimsa silk is promoted in parts of Southern India for those who prefer not to wear silk produced by killing silkworms.[22][23][24] Retrieved October 17, 2010 from http://www.wikipedia.org/wiki/Silk
References:
19. ^ Carry Gleason: The Biography of Silk, page 12, Crabtree Publishing Company, 2007.
20. ^ "Down and Silk: Birds and Insects Exploited for Fabric". PETA. http://www.peta.org/mc/factsheet_display.asp?ID=121. Retrieved 2007-01-06.
21. ^ "Mahatma Gandhi: 100 years", 1968, p. 349
22. ^ Silk Moths Fly Free Kusuma Rajaiah's Ahimsa project.
23. ^ Silk saree without killing a single silkworm Another article about Rajaiah and his methods.
24. ^ Peace Silk The main source for cruelty-free silk in the United States. • Kolander, Cheryl. 2000. "Silk Workers Notebook", 3rd ed.
• Good, Irene. 1995. "On the question of silk in pre-Han Eurasia" Antiquity Vol. 69, Number 266, December 1995, pp. 959–968
• Hill, John E. 2004. The Peoples of the West from the Weilüe 魏略 by Yu Huan 魚豢: A Third Century Chinese Account Composed between 239 and 265 AD. Draft annotated English translation. Appendix E.
• Kuhn, Dieter. 1995. "Silk Weaving in Ancient China: From Geometric Figures to Patterns of Pictorial Likeness." Chinese Science 12 (1995): pp. 77–114.
• Liu, Xinru. 1996. Silk and Religion: An Exploration of Material Life and the Thought of People, AD 600-1200. Oxford University Press.
• Sung, Ying-Hsing. 1637. Chinese Technology in the Seventeenth Century - T'ien-kung K'ai-wu. Translated and annotated by E-tu Zen Sun and Shiou-chuan Sun. Pennsylvania State University Press, 1966. Reprint: Dover, 1997. Chap. 2. Clothing materials.
• Kadolph, Sara J. Textiles. 10th ed. Upper Saddle River: Pearson Prentice Hall, 2007. 76-81. .
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