SILK

SILK

What is it?

Silk is a natural fiber made up of proteins. Also known as silk is the wide variation of fabrics made with this fiber.

Although produced by several groups of arthropods, such as spiders and various types of insects, currently only the silk produced by butterfly larvae - the "silkworm" - is used in industrial textile manufacturing. There has been some research in search of other types of silks with different properties, which differ at the molecular level. In general silks are produced mainly by insect larvae before they complete their metamorphosis, but there are also cases of silks produced by adult specimens.

Silk secretion is especially common in arthropods (bees, wasps and ants), and is sometimes used in nest building. Other arthropods also produce silk, in particular various arachnids, such as spiders.

There are several arthropods that produce silk, among which we can mention: spiders, larvae of frigáneas and embiópteros.

History

Silk fabrics were first made in ancient China; Some indications indicate that they were already made around the year 3000 a. C., although there is more solid evidence that the silk was used more widely towards the year 1300 a. C. Legend says that by then the Empress of China wore silk dresses. At first silk was a fabric reserved exclusively for members of the Chinese imperial family, both for their own use and to be given away. But over time, given its increasing use through the Chinese culture ended up extending its production, both geographically and socially, to other areas of Asia.

Silk quickly became a luxury product highly appreciated by merchants, due to its texture and shine, in addition to being a very accessible and convenient to carry. Therefore, this product came to have a strong demand, becoming a basic element of pre-industrial international trade.

In 2007 archeologists discovered in a tomb in Jiangxi Province remains of a dress, whose silk fibers were tightly woven and dyed, dated around the time of the Eastern Zhou Dynasty, about 2500 years old. Although historians suspect that the formation of the silk-related Chinese textile industry was a long process, one knows the search of the way to be able to use the silk fabrics by means of "complicated techniques" with which the fabric was treated and had.

The first test of the international trade of silk was the discovery of a silk fiber in the hair of an Egyptian mummy of the 21st dynasty, around the year 1070 a. C. Ultimately, the silk trade reached as far afield as the Indian Subcontinent, the Middle East, Europe, and North Africa. This trade was so widespread that the set of major trade routes between Europe and Asia came to be known as the Silk Road.

The emperors of China strove to keep secret the knowledge of sericulture to preserve the monopoly of their country. Even so, the sericulture arrived in Korea around the year 200 a. About the first century after Christ had already reached the ancient Khotan and by the year 300 d. C. silk production was practically established in India.

Applications

The good absorption of the silk makes it comfortable to wear clothes made with this fabric in warm climates and in situations of physical activity. Its low conductivity keeps warm air close to the skin during cold weather. It is often used to make clothing such as shirts, blouses, formal dresses, haute couture, pajamas, gowns, and underwear.

The elegance of the silk, its soft luster and beautiful fall make it perfect for some upholstery applications. Used for walls, curtains (if mixed with other fibers), carpets, bedding and wall hangings.

Silk was also used for the manufacture of parachutes until the appearance of nylon and ripstop, bicycle tires, to fill the duvets and to manufacture bags of gunpowder artillery. The first bulletproof vests were made from silk in the powder era until about World War I.

A special manufacturing process makes it suitable as a surgical suture not absorbable by the body. Chinese doctors have used it to make prosthetic arteries. The silk cloth can also be used as a material on which to write. Silk has always been much appreciated, symbol of luxury and wealth.

Culture

To begin with, silkworms lay their eggs on specially prepared paper. The eggs hatch and the caterpillars (silkworms) are fed with fresh leaves of mulberry. After about 35 days and 4 skin changes the caterpillars are 10,000 times heavier than when they were born and are already able to start spinning a cocoon.

A cane frame is placed on the tray with the caterpillars and each one begins to spin a cocoon by moving its head in a pattern-shaped movement of 8. Two glands produce the liquid silk and force it to leave through apertures in the Head called spineretes.

The liquid silk is coated with sericin, a water-soluble protective gum, which solidifies in contact with the air. For the next two or three days the caterpillar rotates about a thousand filaments upon itself and is completely enclosed within the cocoon. Most caterpillars are boiled in boiling water and carefully removed from their cocoon; Some are allowed to metamorphose into moths to breed the next generation of caterpillars.

Getting Thread

The drooping buds are classified by the fiber size, their quality and their defects and then are brushed to find the filaments. Several filaments meet and are curled on a wheel. Each cocoon produces approximately 1500 meters of fiber. Several filaments combine to form a thread. As the fibers combine and wrap in the coil can be rolled to hold them together. This process is called "stretched" and the resulting fiber is called "stretched thread".

The type of yarn and the amount of twist refer to the fabric produced. The finest coiled wire type is known as "single", where eight filaments are coiled together. The unique yarns can be two or three turns per inch and are used to fill the threads in the silk factories.

Silk scraps are produced from the inner portions of the cocoons. These are degummed and spun just like any other basic fiber. Or it can also be mixed with another type of basic fiber and spun into a yarn.

The production of "wild silk" is not controlled. The buds are collected once the moths have left them, so they are often destroyed and the collected silk is usually of poorer quality. The fiber can not be rolled up and has to be spun thoroughly. Wild silk types include silk Tussah (most common), Dupioni and finally, Momme.

Animal rights

Since the cocoons are introduced with the caterpillars inside in boiling water to drown them, sericulture has been criticized at the beginning of the 21st century by animal rights activists, especially since the appearance of artificial silk. This led to the development of a cotton spinning machine that Gandhi distributed for his country that can still be seen at the Gandhi Institute. Ahimsa silk, made from the wild and semi-wild cocoons of silk moths, is promoted in parts of southern India by those who prefer not to use the silk produced by drowning the caterpillars inside their cocoons.

Nerea Aragunde Pintos

4ºESO C