SILKIntroduction The ancient Chinese were credited with the discovery of silk and thecultivation of silk worm. They were able to guard the secret of sericulture and it took about3,000 years for the outside world to know anything about it. Theorigin of silk is shrouded in myths and legends. According to onelegend, a little Chinese princess accidentally dropped a cocoon intoa cup of tea. Later her mother was started to find that a fine strandcould be unwound from softened cocoon. In the third century A.D., some Chinese maidens, who weresericulture experts, were mysteriously kidnapped and carriedthrough Korea and Japan, where they instructed the people of thecourt and later Japanese craftsmen who soon produced silk quicklyand scientifically. Silk is continuous protein filament extruded by silk worm. Itpossesses all the desirable properties of a textile fibre. It is solidifiedprotein produced by certain caterpillars which will encasethemselves in the form of cocoon.Types of Silk MULBERRY SILK As the name indicates, are produced by wormswhich feed on mulberry leaves. Most gorgeous and fabulous silkmaterials are produced out of this variety. Sarees fromKancheepuram, Kashmir, Baranasi and Mysore belong to this variety. TASSAR SILK A tribal variety silkworm is raised in forest trees ofSai, Arjun and Asan. Madhya Pradesh, Bihar and Orissa are theprincipal Tassar-producing States, accounting over 90 percent of thetotal production. Clothings made out this variety have a Dry Look.They have the subdued brilliance of morning sun. ERI SILK It is produced from philosammia ricini worms foundextensively in Eastern India, part of China and South East Asia. TheEri culture extends up to an altitude of 1500 meters in the hills and ispracticed in temperatures varying from 12Cin winter to 37C insummer with a humidity of 80 to 100%. Eri worms are reared indoors. MUGA SILK It is produced only in the north-eastern region of India.This golden Yellow silk is produced by a Muga worm. This variety iscultured mostly in the Brahmaputra Valley.The worm feeds on Somand Soalu leaves and produces a golden yellow silk.Silk producing countries in the worldThe main silk producing countries in the worldare: Japan, China, Russia, India, Italy, Korea,Turkey, Iran, Brazil, Spain, France, Syria, andAustria.Life Cycle of Silk WormLife Cycle of Silk WormEGGEggs that have been selected are kept in cold storage for approximately six weeksafter they are laid. Then, they are placed in incubators where they remain until allare hatched after 12 to 15 days. One ounce of egg yields as many as 36,000 silkworms. When the worms appear perforated paper is placed over them and a supplyof chopped mulberry leaves is spread on the paper. The worms climb through theholes, dirt and egg-residues are left behind.Life Cycle of Silk WormCATTERPILLARIt is a larva about 1/4" in length. The larva requires careful maturing in a controlledatmosphere for approximately 20 to 30 days. During this period they are fed on finelycut mulberry leaves 5 times a day. During this period the silk worms do nothing buteat, except four periods of sleep lasting a day at a time during which they shed theirskins and grow new ones (molting). After its fourth molt, the silk worm settles down toa final feed lasting about 10 days, during which it eats 20 times its own weight ofleaves. It is over 3 inches long and weighs about 5 gms.The worm is now fully grown and it stops eating and begins to spin filaments. Theliquid silk (known as FIBROIN) is present in two glands in the silk worm. From theseglands it flows into two channels to a common exit tube called, the spinneret in thesilk worm head. As it emerges the liquid silk hardens into very fine filaments andthese are coated and cemented together by a gummy substance called Sericin whichcomes from two other glands nearby. As the silk emerges, the silk worm moves itshead backwards and forwards in a figure. Gradually it surrounds itself with a stronglybuilt cocoon made from a continuous silk strand. Spinning usually takes 2 to 3 days.Life Cycle of Silk WormCHRYSALIS OR PUPAAfter finishing spinning, the enclosed silk worm undergoes a remarkabletransformation, passing from the form of a caterpillar into an inert chrysalis or pupa.If left undisturbed, the pupa inside the cocoon develops into a moth, within twoweeks. The moth escapes from the cocoon by secreting a fluid that dissolves awaya section of the cocoon to make a hole through which the moth crawls out. Thecontinuous silk filament is thus broken up into thousands of short pieces which areuseless for reeling. So within a few days of making its cocoon the pupa must bekilled by steaming. Some good cocoons are kept for breeding.Life Cycle of Silk WormMOTHThe moth emerge from the cocoons are small grayish white insects and lives only afew hours. They cannot fly; they have no mouth and cannot eat. The sole job of thesilk worm is to mate and lay its batch of 300-400 eggs. After laying eggs, the mothdies.Method Of Extraction Of Silk From Cocoon AndProcess Of Preparing Filature SilkSilk ReelingSilk is quite different from other natural fibers which areproduced in relatively short length. Silk worm makes itscocoon from a twin filament that extruded from its spinneretin a continuous strand. This filament may be as a mile inlength. The production of a thread or yarn of silk suitablefor weaving is therefore a process different from that whichis used in the case of shorter fibers. All that is necessary inprinciple is to unwind the long continuous filaments from thecocoons and then twist a number of these together to form athread of useful thickness.The unwinding of the fine silk filaments from the cocoons iscalled reeling. Since a single filament is very thin a finitenumber of cocoons are reeled together and combined in theform of thread without twist. Reeling consists of the followingoperations.Method Of Extraction Of Silk From Cocoon AndProcess Of Preparing Filature SilkStiflingHere, the moths inside the cocoons are killed by steam orhot water.GRADING OR SORTINGTo obtain uniform and good quality yarn, silk grading isdone. Cocoons of different sizes are grouped together;damaged and ill-developed cocoons are rejected and usedin the waste industry.COOKINGThe sorted cocoons are placed in 1% hot soap solution at90C in a vat to soften the sericin gum and to enable thefilaments to be drawn out easily as one continuous thread.Good cooking is essential for the success of subsequentoperation and it is done for a few minutes.Method Of Extraction Of Silk From Cocoon AndProcess Of Preparing Filature SilkBRUSHINGAfter cooking, the unreelable discontinuous and rough mass of fiberscalled floss, is removed with a brush until the free end from which thecontinuous length is found Floss is used in the waste industry.Cocoons, after brushing are transferred to a basin containing water keptat 60C. Reeling requires great skill, as the operator must produceuniform thread by combining the silk filaments in suitable fashion. Eachfilament is narrower towards the beginning and the end than it is in themiddle. The denier may also vary from cocoon to cocoon. The reelermust so manipulate that the cocoons are so adjusted as to produce auniform yarn.To produce a silk thread of 28 to 30 denier, 15 to 18 filaments arecombined. The required number of filament are brought together to forma thread by drawing them over a glass roller and then through aporcelain guide, drilled with vertical hole gauge to denier required.Method Of Extraction Of Silk From Cocoon AndProcess Of Preparing Filature SilkCROISSUREIf the silk filaments are simply drawn together the results would beribbon or a tape. So to obtain a cylindrical thread it is necessary to havea device called croissure, which causes crossing of the threads severaltimes with itself to dissipate water and to assist cohesion of silkfilaments.If the temperature of the reeling bath is hot, the silk comes off veryquickly. If it is too cold, it comes off with difficulty and cause breakage,so the temperature must be kept in moderate condition.The silk filaments after passing through the croissure device passesthrough guide eye set on sliding rod having to and fro motion across thedirection of the thread. Then the filaments are wound on the rotating sixarmed winding reeler in the form of skeins. These are made up intobundles of about 6 lbs called books. The books are then packed intobales for shipment.Method Of Extraction Of Silk From Cocoon AndProcess Of Preparing Filature SilkDEGUMMED SILKThe natural gum sericin is normally left on the silk during reeling,throwing and weaving. It acts as a size which protects the fibres frommechanical injury. The gum is removed from the finished yarns orfabrics, usually by boiling with soap and water.Silk fabrics, woven with the sericin still on the yarn, have a characteristicstiffness of handle; they are also dull in appearance. After degumming,the silk acquires its beautiful luster and becomes soft. As much as one-third of the weight of the fabric may be lost when the gum is removed inthis way.Raw silk with the gum still on the filaments is called hard silk.Degummed silk is called soft silk.Georgette, chiffon and crepe fabrics are woven from hard silk which isafterwards degummed.Method Of Extraction Of Silk From Cocoon AndProcess Of Preparing Filature SilkThis is the operation of twisting of long filaments of silk intoa yarn. Reeled silk is transformed into silk yarn by thisprocess called silk throwing. Twist gives cohesion to thethin filaments which are combined together. In throwing thenumber of TPI (Twist per Inch) inserted and the direction oftwist (S or Z) are important.The raw silk skeins are soaked in worm water with soap.The softening of the sericin gum aids the easy handling ofthe filament. After mechanical drying, the skeins are placedon light reels from which the silk is wound on bobbins. Thethread is then inspected and packaged and is ready forshipment to manufacturers for construction of fabrics.Types of Thrown Silk ThreadsSeveral kinds of silk yarn or threads are used in the manufacture of silk goods.The types of yarn and the amount of twist depend on what the weaver desires.SINGLES3 to 8 strands of silk filaments are twisted together in one direction to form ayarn called a single.Loose twist singles having 2 to 3 TPI. It is used as weft yarn in many silk fabrics.Hard twist singles having much greater number of TPI. It is used in the sheerfabrics.TRAMThis is a lightly twisted thread formed by twisting 2 or 3 untwisted singles of silktogether. Low twister tram will have only 2 to 3 TPI; high twist tram will have 12to 20 TPI. Tram is moderately strong, it is soft and has a full handle. Tram yarnsare used as weft in woven fabrics.ORGANZINEIt is composed of 2 or more singles, each of which are 15 TPI. These singles arethen combined by twisting them around each other in the opposite direction with12 to 30 TPI which cause them to interlock more tightly resulting in a firmerstronger yarn.Types of Thrown Silk ThreadsCREPEIt is composed of each of 2 pairs of untwisted singles. One pair istwisted 60 to90 TPI in one direction, the other is twisted the samenumber of TPI in the opposite direction. They are then twisted aroundeach other with 3 to 5 TPI. These yarns are used for crepe fabric andchiffon and for knitting into hosiery.GRENADINEThis is a tightly twisted yarn in which 2 or 3 twisted singles are combinedand twisted in the opposite direction. It is twisted more tightly in theopposite.Grenadine yarns have extra good weaving qualities and a delusturedappearance. They are used for such sheer fabrics as organdy andgrenadine. They are also used for high quality silk hose.COMPHENZINEThis yarn is made from two tightly twisted singles and one untwistedsingle yarn. When these are twisted together with 5 TPI the untwistedyarn crinkles up, giving the knobby appearance characteristic of crepethreads.Method Of Extraction Of Silk From Cocoon AndProcess Of Preparing Filature SilkSEWING SILKSThese are tightly twisted strong yarns. They are made by twisting 2 or 3silk singles together and then combining several of the resulting threadsby twisting in the opposite direction.TWO BY TWOEach of two pairs of untwisted single is twisted about 36 TPI and thentwisted around each other with 25 to35 TPI in the opposite direction. Theyarns are much like the Grenadine yarns but are heavier. Their weight,body and high twist make them desirable for crepe fabrics.EMBROIDERY SILKThese are often simple untwisted singles united by a slight twist.Types of Thrown Silk ThreadsSILK NOILThe waste derived from the processing of spun silk yarn is also used.Trade practice rules of the Federal Trade Commission require that suchfiber be labeled as waste silk, silk waste, noil silk or silk noil. For obviousreasons, the last two designations are most frequently used. Silk noilmay be processed into spun yarns and woven into textured fibers fordraperies, upholstery and sportswear. These fabrics are dull and roughand have cotton like appearance but are generally more resistant.PURE-DYE SILKAs silk is weighted during the dyeing process, the term pure- dye silkindicates that weighing was not added at the tone. According to theFederal Trade Commission, pure-dye silk is defined as a fabric madeexclusively of silk fibres containing no metallic weighting whatsoeverUses of SilkBecause silk prevents body heat from radiatingoutward, it is desirable for winter apparel. Silkyarn is used to produce such sheer fabric asgeorgette, taffeta, organdy and grenadine. Spunsilk is used for shantung and pile fabrics, fordress trimmings, linings, and elastic webbingand for velvets for umbrella fabrics and forinsulative material. Wild silk fabrics are durableand have a coarse irregular surface. Typicalfabrics are shantung, tussah and pongee.