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.
Tussar silk
In order to kill the silkworms, the cocoons are dried in the sun. A variation of the process exists in which the silkworms are allowed to leave before the cocoons are soaked in boiling water to soften the silk and then reeled. Single-shelled, oval-shaped cocoons are collected and then boiled to extract the silk yarn. Boiling is a very important part in the manufacturing of silk, as it softens the cocoon and makes the extraction of silk easier. In conventional sericulture, the cocoons are boiled with the larvae still inside; however, if the cocoons are boiled after the larvae have left them, the silk made is then called "non-violent silk" or "Ahimsa silk". In China, the silks are given different names when silkworms are reared on different plants, as the diet of the silkworms has an effect on the quality of the silk. For example, silk from larvae on the wild mulberry is called "zhe", while those on the oak "Quercus dentata" produce "hu".