Raw silk is the silk as it is reeled from the cocoons.
Gloss silk is the loose silk that envelops the cocoons.
Two or three threads of raw silk, twisted loosely two or four times to the inch, is called tram, and is used as shute or woof. In weaving, the woof has little or no strain upon it, and it fills the warp better by being soft and loose.
The warp, which is also called organzine, is made of the finer and more regular threads of silk tightly twisted so as to produce strength and elasticity in the fabric.
Amongst the animal fibres, the first place must be assigned to silk not only on account of the beauty of the fibre itself, but also because no other textile fabric combines to such a degree the qualities of warmth, brightness, strength, firmness, and durability.
It is the natural production of the silkworm. The eggs are hatched in spring, and the worm or caterpillar grows rapidly, until when fully grown it is about three inches long. It feeds on the leaf of the mulberry tree.
Like most other caterpillars, the silkworm sheds its coat four times, at intervals depending on the quality and quantity of the food. When about to spin its cocoon, it ceases to eat. The silk is produced from two long glands along the sides of the body. From each gland comes a slender tube. These tubes unite into one near the mouth. In spinning its cocoon, the worm sends out a line of thread about four thousand yards in length. In doing this, it bends its head and body backward and forward until it has entirely surrounded its body with silk, and within this it spins a finer and more delicate silk.
The cocoon is generally completed in about three days, and it is about the size of a pigeon's egg.
When the cocoons are finished by the worms, they are placed in vessels heated with hot water or in an oven which melts the cementing gum and kills the chrysalis. They are then sorted and placed in hot water and stirred until the winder is able to catch a number of loosened ends which she winds together on reels as one thread. This thread then goes to the spinning frame, where the fibres are twisted into the required thickness for weaving.
The value of silk depends on, first, lustre; second, strength; third, fineness. Its appearance under the microscope is an even, round, glasslike fibre; its strength is said to be three times that of linen. No other textile fibre can be spun to such a degree of fineness combined with elasticity.
The silk industry doubtless originated in China, and there is exported from that country nearly seven million dollars' worth of silk annually. When first.known to the
Romans, silk was so dear that it was sold weight for weight with gold. The high-priced silk fabrics have long come from Italy and France, and the cheaper ones from the United States, India, Persia, and China. The silks of the United States have greatly improved in quality in recent years.
Silk is said to rank next to wool as a non-conductor of heat.
Varieties of Silk Cloth.
Most manufactured silk materials are known under one of the following names:
Satin, a silk fabric of a thick, close texture, with a glossy face and a dull back; the lustre of the surface is produced partly by the quality of the silk and partly by a method of weaving that reduces the number of crossings of filling and warp. The surface is made still more lustrous by being made to pass over very hot rollers in finishing.
Taffeta, a light-weight, smooth-finished silk, capable of repelling dust. It is frequently used for linings. It may be plain, figured, striped, or plaid.
Changeable silk, in which the warp and woof are of contrasting colors.
Surah, a soft twilled silk with a glossy surface usually of solid color.
Gros Grain, a dull-finished silk with a cord running across from selvage to selvage.
Faille Frangaise, a fabric woven in the same manner as gros grain, but softer and finished with considerable lustre.
Irish Poplins and Bengalines 'belong to this family, although the latter are frequently mixed with either linen or wool.
Ottoman is a very heavy corded silk, used for cloakings.
Damasse (see Damasse in wool), sometimes called brocade.
Foulard, a soft twilled silk frequently printed in contrasting colors.
Moire or watered silk. This effect is produced by subjecting gros grain silk to various conditions of heat, moisture, and pressure.
China and Japanese silks are frequently spoken of as wash silks. These are particularly desirable for summer dresses because of the lightness and coolness of the fabric, as well as the fact that they may be washed like gingham.
Crepe. This is a sheer silk fabric, which, by being exposed to heat and moisture, is given a peculiar crinkled effect; when dyed black, it is used for mourning.
Armure and Matalass/ (see woolen materials).
Pongee, a soft bleached wash silk made in China, the product of a wild silkworm that feeds on the oak leaf.
Velvet, a silk fabric closely woven and having on one side a thick, short, smooth nap or cut pile. Velvets are sometimes made of all silk, but frequently have a cotton back with silk surface.