Silk
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 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 heat the cocoons to kill them, 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.
History of silk
Silk was made using various breeds of lepidopterans, both wild and domestic. While wild silks were produced in many countries, there is no doubt that the Chinese were the first to begin production on such a large scale, having the most effective species for silk production, the "Bombyx mandarina" and its domesticated descendent "B. mori". Chinese sources claim the existence of a machine to unwind silkworm cocoons in 1090. The cocoons were placed in a large basin of hot water, the silk would leave the cauldron by tiny guiding rings, and would be wound onto a large spool, thanks to a backwards and forward motion. Little information exists about spinning techniques in use in China. The spinning wheel, in all likelihood moved by hand, was known by the beginning of the Christian era. The first accepted image of a spinning wheel appears in 1210. There is an image of a silk spinning machine powered by a water wheel that dates to 1313.