Natural Fibers

Sericulture requires scrupulous care and painstaking attention to detail. Breeder moths are first selected with great care. Eggs from the moths are repeatedly tested to ensure the quality of the larvae. The selected eggs are placed in cold storage until the early spring when they are incubated. After about a week, the eggs hatch into tiny silkworms. The worms are kept in clean conditions on trays of mulberry leaves. Young silkworms have voracious appetites, eating every couple of hours day and night for five weeks. To produce a pound of silk, one silkworm would have to eat 200 lb (90.8 kg) of mulberry leaves. In these first five weeks of life, the worms grow to 70 times their original size.

Once the silkworm's appetite has been sated, the worm is placed on a pile of straw or heather, where it begins spinning its cocoon. The silkworm first attaches itself to a twig. Then it begins spinning filaments of silk in an endless series of figure eights. This builds up walls within walls which are held together by gummy sericin that dries and hardens following exposure to air.

Without human intervention, the worm inside the cocoon would develop into a chrysalis and later into a moth. The moth would then burst the cocoon and break the one long strand of silk into many short ones. But sericulture destroys the worm inside the cocoon by stifling it with heat.

The next step in sericulture is to unwind the cocoon. This process is called reeling. To produce uniform strands of raw silk for commercial use, filaments of 5-10 cocoons are combined into a single thread. To do this, the cocoons are first soaked in hot water. After the ends of the filaments have been located, the filaments are passed through porcelain guides where they are twisted into fibers of uniform length and regularity. Reeling may be done automatically or by hand.

Raw silk is wound into skeins. Thirty skeins constitute one book, which weighs around 4.3 lb (1.95 kg). Thirty books make a bale, which weighs 132.3 lb (60.06 kg). The bale is the basic unit of commercial transactions. About 900 lb (408.6 kg) of cocoons are required to produce one bale of raw silk.

Raw silk taken directly from the filature is too fine to be woven. It must first be made into a thicker and more substantial yarn in a process known as throwing. Throwing consists of: sorting the skeins according to quality; soaking selected skeins to remove the sericin; drying any skeins that have been soaked; rewinding the skeins onto bobbins; twisting the threads from two or more bobbins to form single strands; again twisting to produce a fine thread; and finally conditioning the highly twisted thread.