Barbara Drummond, age 13, of New Bedford, Mass., for her question:
HOW IS SILK OBTAINED?
Silk is the thread or cloth made from the fine web of a caterpillar called the silkworm. The caterpillar comes from a small grayish white moth called Bombyx mori, which feeds on the leaves of the mulberry tree.
Silkworms are raised in China, Japan, India and in parts of Asia minor as well as in France, Spain. Italy and Brazil. There have been attempts to raise silkworms for commercial use in the United States but so far these attempts have always failed. It is only where labor is cheap that silk raising is profitable.
Making silk today is a science. Silkworm eggs are carefully stored on strips of paper or cloth. When the mulberry trees bear a fresh crop of leaves, the eggs are warmed to the right temperature for hatching. The tiny worms hatch and are placed in trays filled with finely chopped mulberry leaves.
Eating constantly day and night, the worms grow to over three inches in length and eat many times their own weight in leaves. Twenty to 30 days are needed for the worms to complete their growth. During this time they shed their skins four times.
When the worms are ready to start spinning their cocoons, they stop eating and begin to move their heads slowly back and forth. Then they are placed on trays with little racks of twigs or straw, to which they attach their cocoons. Fine silk threads are spun from spinnerets on the worm's head. The spinning of the cocoon takes about three days.
Several weeks or months later the threads are taken from the cocoon for use as silk. This is called reeling the silk. The cocoons are exposed to heat and steam to kill the chrysalis within each one.
Each cocoon is made up of a double thread of silk filaments. Cocoons are placed in troughs of warm water. the twin filaments from five to six cocoons are then brought together through a small ring or guide and over a reel. Up to 1,200 yards of silk may be reeled from a single cocoon.
The silk reeling houses are called filatures. The reeling, formerly done by hand, is now done by machines. The reeled silk is twisted into skeins and then made into books of about 30 skeins each. Thirty of these books are packed into a bale, which weighs about 130 pounds.
When the silk reaches the factories, it is graded for evenness, cleanliness and size. The skeins are then soaked in soap and oil to loosen the natural gum and to make the threads softer. The softened skeins are wound on bobbins.
Two or more bobbins are placed side by side and the thread from both are wound together on another spool. This is called doubling. Usually some twist is given to the thread.
This doubling and twisting of the threads are called throwing. Thrown silk is used in sewing thread and in fine woven and knitted fabrics.
Many cocoons are parts of cocoons cannot be reeled because the fibers are broken and short. This silk, called waste silk or frisons, must be spun like cotton. This spun silk makes a soft thread, used for embroidery floss, linenlike silks, silk suitings and soft fabrics.