One of the strongest and most luxurious fabrics in the world, silk has a long history. The cocoons, or casings, of the silk moth have been used for weaving fine fabric in China for almost five thousand years. The philosopher Confucius (551–c. 479 B.C.E. ) told the story of Empress Xi Ling-Shi, who had a silk cocoon drop from a mulberry tree into her cup of hot tea and discovered the cocoon's strong and very long silk filaments. It was the empress who, around 2640 B.C.E. , organized the harvesting and weaving of these long strands into silk. (Most historians believe that this story about the origins of silk production is not based in fact, but they do not know the exact origins.)
At first the Chinese carefully confined production to their own use, but demand for the lustrous fabric of China's imperial court spread. Traders seeking silk soon created an overland route to China that became known as the "Silk Road." By 139 B.C.E. the Silk Road had become the world's longest highway, stretching from eastern China to the Mediterranean. For years it was the principal east-west trade route for goods and ideas.
The Chinese were careful to protect their secret methods, searching travelers at the borders for cocoons or eggs. By 200 C.E. , however, Chinese immigrants established silk industries in Korea and Japan. About one hundred years later silk began to be produced in the Indian subcontinent. Later the silk moth was secretly exported to the Byzantine Empire (476–1453 C.E. ) in the Middle East by Persian monks, from present-day Iran, who smuggled the cocoons out in their hollow canes. They established a new silk industry in Constantinople, modern-day Istanbul, Turkey, under the protection of the emperor Justinian (483–565 C.E. ). The silk worm was only introduced to Europe in the thirteenth century when Christian crusaders (those who fought to gain control of the Holy Land from the Muslims) traveling in the Middle East brought silk weavers from Constantinople to Italy.
The silkworm is actually not a worm at all but a caterpillar. Although it is thought to be a native species of China, there are no longer any silk moths living in the wild anywhere in the world. All that exist are raised to make silk.
After the domesticated silkworms are born, they eat exclusively mulberry leaves and constantly for about a month, increasing their weight by ten thousand times and shedding their skin four times. When they have eaten enough, they begin to produce a jelly-like substance made of protein that hardens when it comes into contact with air. At the same time they produce a gum called sericin to hold the filament together. After three or four days they have spun the cocoon, which looks like a puffy white ball. In eight or nine days the cocoons are killed by steam or baking, placed in water to loosen the sericin, and unwound. The filaments average 650 to 1,000 yards long. Between five and eight of them are twisted together to make one thread.
Today China and Japan produce over half of the world's silk. Silk is known for its resiliency, elasticity, and strength.