Silk is a fiber which is widely used in textile sector to produce cloths. Silk is a protein composed of fiboin. Larvae of a lot of insects produce silk while forming their cocoon. Mulberry silk is regarded as one of the best qualities of silk and is produced by Bombyx mori silkworm. Silk has a triangular prism structure and this results in a shiny and glossy appearance of silk. The prism structure of silk refracts light and produces different colors. Silk from different insects differ minutely in structure and types. When larvae are going through metamorphosis , they produces silk. Only few insects produce silk throughout their life cycle. Web spinner is one such insect. Bees, silverfish, flies, fleas, spiders and thrips produce silk as well. Wild silk was used in China in ancient times. It was not as prevalent as cultivated silk as wild silk was less uniform than cultivated silk and it was difficult in general to gather wild silk due to natural causes. Cultivated silk is collected by dipping the silkworm pupae in boiling water and spinning the entire silk thread. With advances in research and development in technology, genetic modification of silkworms is being employed to better silk production. Silk production and use goes back five thousand years. The Chinese used silk extensively. India also has a history of silk production and trade which goes back to Indus valley civilization. Silk is in use in European, middle east and Asian countries for the last few thousands years.
Silk farming involves rearing of silkwroms and this activity is called sericulture. Mulbury leaves are the primary food for the larvae of Bombyx Mori. The larvae, while completeing metamorphosis, start developing silk coccons. They secrete fuids from their glands and their fluid results in the formation of fiber for the development of the cooocn. The silk fiber is a protein. It is secreted by glands and cemented by sericin, another fluid secreted by the wrms. To remove serium and obtain silk, larvae are put in boiling water to free the silk fiber and make them ready for silk collection. The filaments thus obtained are converted into thread and then yarn. The yarn are woven into a silk cloth. The various phass in silk productions start when a silk moth lays eggs. The eggs hatch and caterpillars are formed which eat mulburryleaves. The caterpillar or the silkworm larvae forms a net and scerets fluis which froms silk. The number of silkworms used to make silk are huge as each larvae produces very limite quantity of silk. Production of silk is labour extensive and leavesmore impact on envir,ment than cultivation of other fibers.
Qualities, use and benefits
Silk has a soft texture and it has a plain shimmery surface.Silk fiber is naturally strong but weakens when silk is dipped in water. Silk fiber hardly stretches and sunlight diminishes silk fiber’s strength. Silk has a high resistance and does not allow electricity to pass through and acts an an insulator. Silk doe not dissolve easily in a majority of acidic solutions. Silk fiber contains proteins which are amino acids with hydrogen bonds between chains. The chains contract on exposure to moisture or sunlight. To make silk wrinkle free, steaming is employed along with a press. Silk is used to make many garments as silk wear are very comfortable. Shirts, blouses, robes, weeding garments, decorative garments, suits and many other cloths are made from silk. Silk resists insects like mosquito and prevents their biting effect. Due to its natural luster and shine, silk is used in wall portraits, furniture seats, covers and beds sheets. Silk is used with other materials in making parachutes, bags, surgical sutures, disposable cups. New areas are being researched to extend the use of silk. China is the biggest producer of silk in the world today. Sea silk is another type of silk which is very costly and highly sought after. Sea silk is produced by Pinna nobilis when it secretes filaments from its gland. The mollusk is found in Mediterranean region and it releases bysscus to attach itself to a rock or on to seabed. Sea silk is very good fiber, better than silk and is used to make expensive fabrics. The fabric made of sea silk is very light. Any raw silk that cannot be winded onto threads or used for throwing process is silk waste. Spiders also produce silk which has high tensile strength and difficult to break. Spider silk is stretchable and absorbs energy. Spider silk has some medicinal properties as well as it is applied on certain wounds to heal. It is difficult to extract spider silk and research is being done to increase its productions and use.