WE ARE SPECIALIZED
GENERALLY TWO SILKWORMS HOLD THE MAXIMUM SILK INDUSTRY PRODUCATION.
- Lepidoptera or scale winged insects.
- Bombyx Mori / mulberry silkworm which produces the major production of silk used in the trade.
Silkworms live on only on the leaves of Mulberry tree i.e. first essential of the silk industry. In Europe, silkworms are fed largely on the white-fruited mulberry. Mulberry leaves growing condition also plays an important role in silk production under which they are growing up and it determines whether the leaves will be suitable for the silkworm or not. Silkworm culture which starts with the proper selection and care of the eggs have developed into a large scientifically controlled industry. Silkworm eggs are of two types:
- Those used for the reproduction
- Those used for the cocoon production
FLOWCHART OF SILK PRODUCTION IS AS FOLLOWS
PRODUCTION AND PROCESSING OF SILK:
1. CULTIVATION OF SILK WORMS / COCOONS ( SERICULTURE)
- After a few days, the eggs are hatch out to tiny caterpillars or ants. I.e. the process of conversion of eggs into caterpillars is known as Hatching. One Ounce of eggs will yield 40000 to 60000 silkworms on hatching. The caterpillars or ant as it is known on first making its appearance is about3mm long (less than an eighth of an inch) and weight is 5 Mg. Its development proceeds with extraordinary rapidly. Every effort is made to get the eggs to hatch out in batches at the same time, as the economy of silk production depends largely on this. The worms will sleep and eat and spin at the same time. Hatching is normally done by the spreading of eggs over trays in the hatching shed. When the worms appear, the perforated paper is placed over them and a supply of chopped mulberry leaves is spread on the paper. The worms climb through holes and set to work on the eaves, dirt, and eggs residues are left behind. Hatching process is completed in 10 to 12 days.
During this stage, the silkworms do nothing but eat except for 4 periods of sleep lasting a day at a time. During which they shad their skins and grow new ones. This period of molting divides the life history of the worm into five periods. The approximate length of each period of the life cycle of the silkworm for the three largest silk producing areas is shown below:
4. THE SPINNING OF THE COCOONS :
EGG PRODUCTION CYCLE:
(Caterpillars – Moulting – Cocoon – Chrysalis – Moth – Eggs) – ( Caterpillars – Moulting – Cocoon – Chrysalis – Moth – Eggs) – (Caterpillars – continuous chain From one ounce of eggs gets up to 140 Lbs of the fresh cocoon. It gives 12 Lbs of raw silk. And to produce it the worms consume a tone of mulberry leaves. As much as the whole sericulture effort is for silk production only sufficient moths are allowed to emerge from their cocoon to supply eggs for the next crop. The rest of the worms are stiffed while in their chrysalis state. By this way, continuity of the cocoon filament will not be broken. In many countries, it is forbidden for silkworm rearing to provide themselves with eggs from their own moths. This is essential to control the many serious diseases to which the worm is prone. Egg production is thus an entirely separated branch of the industry and is carried out under rigorously controlled continuous. The moths emerge from their cocoons as small, greyish white insects with rudimentary wings. They can’t fly; they have no mouths and can’t eat. The moth is to mate and lay its batch of 350 to 400 eggs. In order to check and control the health and vitality of the worms for spinning, each month after mating is put into a linen bag about 2-inch square. This has previously been cleaned and disinfected. After its eggs have been laid, the moth dies. Its body is examined microscopically. And if germs are present then the bag and content are burned. In addition, some of the eggs or seeds as they are called by the rearer are crushed and examined. If they are germ-free then the eggs are passed for hatching.
PETS AND DISEASES:
This carefully control of silkworm eggs have been made necessary by the fact that the silkworm is particularly susceptible to various diseases which become or less epidemic in character. The common diseases of the silkworm are as follows:
- PEBRINE: This disease is hereditary and is caused by the protozoan parasite (Nosema and Bombycis). Worms affected with this disease developing slowly, irregularly and very unequally and also shows black spot on their skins.
- FLACHERIE: Flacherie is the disease which may be due to the infective organisms or by the digestive disorder because of atmospheric conditions and lack of ventilation in rearing rooms. It causes a swelling and blackening of the insect’s body during the last stage due to fermentation in the digestive tract. It is not inherited.
- GRASSERIE: Grasserie is a virus disease and is caused by the mismanagement of the worms at
moultingperiods and uneven feeding. Due to this disease, the worms get restless, become yellow and bloated. When punctured they exude a field matter with minute granular (tissue) crystals.
- MUSCARDINE: Muscardine is a fungus disease and is the most contagious of the silkworm disease which kills the worm quickly. Its appearance should be promptly checked by careful fumigation with burning sulfur. At first, this disease does not exhibit any external characteristics but the vitality of the worm is slowly impaired and it feeds and moves but very slowly. The body becomes reddish in color and gradually contracts and loses its elasticity. The worm usually dies in 20 to 30 hours after the first symptoms of the disease. The dead body dries up and becomes covered with a white alkaline efflorescence. The disease is caused by a minute fungus the spores of which takes root in the body of the worm and finally fill the entire body.
- FLY PARASITE: The fly – Tricholygasorbillaia, one of the tachina flies is a very serve pest of silkworms, especially in the subtropical countries (hot countries). If the mother fly gets into the rearing room she lays her eggs on the silkworm’s body. As the eff hatch maggots eat their way into the body of the silkworm spot in the body wall. If the eggs have been laid late in the life of the worm, the maggot emerges after the cocoon has been spun thus eating the silk, breaking the filament and ruining the cocoon for reeling as the continuous filament will be broken into smaller lengths. Protection against this pest is a proper screening of rearing rooms and the burning of infected worms-
5. SILK REELING:
Vegetable fibers such as cotton and hair fibers such as wool have one thing in common. They are produced in relatively short lengths. Cotton and wool fibers are usually a few inches long. Even flax which is one of the longest of the vegetable textile fibers is only about 2 feet in length. In order to convert these short fibers into long threads or yarns, we have to align the fibers and then spin them by twisting the fibers together. In this way, short fibres are made to grip one another to form a thread or yarn that is long enough to be used for weaving purpose. Silk, however, is quite different from there other natural fibers. The silkworm makes it cocoon from its twin filament that is extracted from its spinneret in the continuous strand. This filament may be as much as a mile long. The double silk filament as it exists in the cocoon is known as the Brave and the single filament is knowns as therein. The production os a thread or yarn of silk suitable for weaving is, therefore, a process different from that which is used in case of shorter fibers. All that is necessary for principle is to unwind the long continuous filament from the cocoons and then twist a number of these together to form a thread of useful thickness. The unwinding of the fine silk filament from the cocoons is called Reeling Process. The process is carried out in a building, a separate department called Filature. Silk reeling is the process by which a number of cocoon babes are reeled together to produce a single thread. This is achieved by unwinding filaments collectively form a group of cooked cocoons at one end in a warm water bath and winding the resultant thread onto a fast-moving reel. Raw silk reeling may be classified by direct reeling method on a standardly sized reel, indirect method of reeling on small reels, and the transfer of reeled silk from small reels onto standardly sized reels on a re-reeling machine. The last technique is primarily applied in modern silk reeling processes. The cocoons are soaked in hot water to soften the sericin gum that is cementing the filament in place. A revolving brushed is used to find the end of the silk filament. It’s a difficult job to search something so fine that it is almost invisible. When the end of the filament is picked up, it is drawn through a guide along with the filaments may be given a slight twist to hold them together and reeled steadily off the cocoons which are left floating in hot water to keep the gum softened. The elementary principles of raw silk reeling are shown below:[Tussah Cocoons are gummed more firmly than those of cultivated silk and contain more calcium salts. They are usually soaked in sodium carbonate before reeling.]
VARIOUS SILK REELING DEVICES
There are many types of silk reeling machines in use.
- Hand spinning wheel- This primitive spinning apparatus is operated by two hands – one to drive the wheel and the other to feed in cocoons. One end of the reeling thread is wound onto each wheel, while cocoons are boiled in a separate pot.
- Charka type reeling machine – The Charka type is in use in India. This machine is operated with separate work motions in reel driving and cocoon feeding to reeling ends by two men per machine. Each machine has 3 ends or more to a reel, which is the same size as the large wheel of the Re-reeling machine in order to save the re-reeling process (direct reeling method).
- Sitting type reeling machine- There are two kinds of sitting type reeling machines, foot operated and motor-driven. The motor-driven reeling machine is not equipped with the stop-motion attachment. There are obstacles to the production of good quality raw silk as the raw silk thread is wound too rapidly to maintain good quality control.
- Multi-ends reeling machine- This machine eliminates the disadvantages of the Sitting type reeling machine by increasing the number of reeling thread ends per basin and reducing the reeling speed. The operator must stand when running this machine as the number of reeling threads per basin increases by twenty-fold. This is also called a “Standing type reeling machine”. Reeling efficiency is unchanged. Quality is better due to reduced speed. The Multi-ends reeling machine is composed of driving part, groping ends, picking ends, standby bath, reeling part,
jetboute, stop motion, traverse guide, small reels, steam heating pipes and clutches. The cooked cocoons contained in the tubs are carried into the groping ends portion of the reeling machine. From there, cocoons are moved into the picking ends apparatus. After correctly processing, the cocoons go to the standby bath for cocoon feeding. They are picked up by the reeler and fed to the reeling thread. During this step, a number of cocoons will be dropped thus reducing the ratio of reeling cocoons per thread. The normal speed of cocoon feeding by a skilled reeler is around 16 times per minute. The reeling thread passes through the jetboat, silk button, first guide, second guider, third guide, fourth guider, traverse guide, in that order and then is wound onto the small reels. The cocoons dropped during the reeling process are gathered and reprocessed starting from the groping end section. The croissant of reeling thread is made between second guider and third guider, and the length of the croissant is not for twisting of the thread but for the cohesion of thread by rubbing of the composed filament. Typically, one set of Multi-ends reeling machines consists of ten basins with each basin having twenty ends or reels.
- Basin: The basin is rectangular with well-rounded corners and edges. It is only 10 to 12 cm deep. It is commonly made of dark-colored porcelain. The basin is subdivided into sections, each intended for a specific job such as brushing, end gathering of
baves, stocks in reserve and waste collection.
- Reels: The reels of the Multi-ends reeling machine have a circumference of 75 cm. The frame of the reel is made of light metal or plastic. The reels are fitted into reel carriers and driven by a transmission shaft by connecting gears.
- Traverse guider: To ensure narrow and long web on the hank of the reel, a cam type traverse assembly has been fixed. This will make a convex surface in the hank, which is wound on the reel. The center part of the hank is higher than the two axes.
- Thread button: Porcelain button thread-guiders are used for removing any dirt adhering to the thread passing through the tiny aperture in the button.
- Hot air partial drying of cocoons: Partial drying of cocoon with a degree of drying around 75 to 80% is recommended instead of steam stifling. The following factors have to be considered during drying of cocoons; The cocoons have to be evenly spread in a thin layer in the trays. Air inlet, outlet, and circulation should be maintained properly. Hot air drying can be carried out using batch type hot air drier or Ushnakoti
- Cocoon sorting: Defective cocoons which are not suitable for reeling have to be separated out using a cocoon sorting table. Cocoon sorting table is made up of a glass top illuminated from the bottom. When the cocoons are spread on the table, defective cocoons can be easily identified and separated. Separation of defective cocoons increases the reeling efficiency. Frequent changes of reeling water can be avoided and good quality of silk yarn can be obtained. The separated defective cocoons can be reeled separately along with double cocoons to produce dupion silk.
- Cocoon cooking: Single pan open cooking method is commonly being used at present. Cocoon cooking in this method is not uniform and
sericineis not softened throughout the layers of shell. This results in reeling breaks which spoils the quality of silk yarn. KSSRDI method of vacuum cocoon cooking method facilitates uniform cooking and with minimum filament breaks. Bivoltine cocoons can be cooked using a circular pressurized method developed by CSTRI.
- Use of Metallic buttons: At present in the reeling process, porcelain buttons are used. Repeated use for porcelain buttons results in ware and tare of the buttonhole increasing its diameter. Also, there is a chance of workers increasing the buttonhole to increase the production resulting in reeling inferior silk yarn. This problem has been solved in the development of metallic button. This is made up of hardnosed steel with a perfect hole size drilled and cannot be altered by workers or ware and tare.
- Croissant: The length of the croissant in the cottage/filature and multi-end basins decides the adhering strength of the silk yarn. It is established that a minimum length of 8 to 10 cms (3-4 inches) has to be maintained on the reeling machine. Installation of the improved croissant pulley is recommended
- Reeling speed: Reeling speed is an important parameter in the production of quality silk yarn. A speed of 160-200 rpm is recommended which will reduce the reeling breaks and also maximizes productivity. Reduction of reeling speed increases the silk quality.
- Denier indicator: The denier of silk filament varies from the beginning to the end of the cocoon. To maintain a uniform denier through a denier indicator has been developed by KSSRDI. When there is a change in the filament denier, the red light glows indicating the reeler to add a cocoon to the reeling ends. Use of denier indicator helps to produce uniform denier silk yarn
- Silk finishing Lacing and Skinning: The silk skeins should be laced at six places using cotton thread. So that the silk threads are retained without entanglement. During lacing and cleaning, extra care should be taken to avoid end breakages in the skeins. The laced silk in the form of hanks is made into the skeins using a skeining machine. The silk is folded and twisted to have five spirals. Care should be taken to avoid any breakage to silk threads during skeining also.
- Bookmaking: Folded (small) skeins are usually made into 2 kg books. The weight of the skeins should be maintained uniformly within a book.
- Long skeining and long skein bookmaking: In order to avoid mishandling of raw silk, it is recommended to practice long skeining and long skein bookmaking (5kg books) using long skeining and long skein bookmaking equipment developed by CSTRI.
- Packing: Packing of raw silk is done in such a way to protect raw silk from damage by moisture and insects. Each book is packed with paper and polythene bag. In the case of small skeins, 20 kg bales are prepared using ten books of 2 kg each and in case of long skeins; 60kg bales are prepared from twelve books of 5 kg each. For transportation purpose, the bales are covered with craft paper and straw mat and placed in gunny bags or cardboard boxes.
- Storage of raw silk: Raw silk quality is affected by fluctuations in temperature and humidity of the storing place and by continuous exposure to sunlight and heat. Silk is also damaged by fungus and insects if not stored properly. Hence, adequate care is required for the storage of raw silk.
ulti-ends reeling machine- This machine eliminates the disadvantages of the Sitting type reeling machine by increasing the number of reeling thread ends per basin and reducing the reeling speed. The operator must stand when running this machine as the number of reeling threads per basin increases by twenty-fold. This is also called a “Standing type reeling machine”. Reeling efficiency is unchanged. Quality is better due to reduced speed. The Multi-ends reeling machine is composed of driving part, groping ends, picking ends, standby bath, reeling part, JetBlue, stop motion, traverse guide, small reels, steam heating pipes and clutches. The cooked cocoons contained in the tubs are carried into the groping ends portion of the reeling machine. From there, cocoons are moved into the picking ends apparatus. After correctly processing, the cocoons go to the standby bath for cocoon feeding. They are picked up by the reeler and fed to the reeling thread. During this step, a number of cocoons will be dropped thus reducing the ratio of reeling cocoons per thread. The normal speed of cocoon feeding by a skilled reeler is around 16 times per minute. The reeling thread passes through the jetboat, silk button, first guide, second guider, third guide, fourth guider, traverse guide, in that order and then is wound onto the small reels. The cocoons dropped during the reeling process are gathered and reprocessed starting from the groping end section. The croissureof reeling thread is made between second guider and third guider, and the length of the croissant is not for twisting of the thread but for the cohesion of thread by rubbing of the composed filament. Typically, one set of Multi-ends reeling machines consists of ten basins with each basin having twenty ends or reels.
AUTOMATIC REELING MACHINE
BRUSHING AND PICKING SECTION –
REELING SECTION –
SEMI-AUTOMATIC REELING MACHINE –
A) REELING VELOCITY (R.V.)
B). GROPING ENDS
C). PICKING ENDS
D). REELING BATH
- Temperature – High temperature in the reeling bath increases the breakdown of the reeling thread, cleanness defects and reduces raw silk yield. It improves the reliability of cocoons, the cohesion and the feel of raw silk by reducing the gum in the sericin. The optimum reeling bath temperature depending on cocoon characteristics is about 30 to 45° C.
- The consistency of water – Continuous reeling work without changing reeling water results in water, which is dense, colored and acid. High-density water reduces the cocoon reliability but increases raw silk percentage making the silk light greyish in color. Water supplied to the reeling bath should be pH controlled so that the water for each reeling bath may remain the same to ensure color uniformity. The best consistency is when the pH of the water is about 6.8-7.0, and the water contains a little diluted and floating sericin.
- Supply of cocoons – In automatic reeling machines, cocoons are supplied in two ways: rotary type and fixed type. In both types, when the size detector is activated, cocoons are supplied one by one, accurately and quickly. In order to raise the feeding efficiency, it is important to minimize the end-missing cocoon supplier and eliminate the floating cocoons.
- Maintenance of size detector – The identification of size by the detector should be accurate. In practice, however, the performance of the detector can be badly affected by improper care, dirt, and abnormal resistance of thread passage and other defects. During operation, the detector should be kept clean and in good repair. Periodic inspections and maintenance should be carried out. • End feeding and button – End-feeding should furnish the end within 1 to 2 seconds without long knots. The hole of the button should correspond to the size of the raw silk
The diameter of the buttonhole should preferably be in the following range:
- Control for the breakdown of a reeling thread – Inefficient processing is considered to be the main cause of the frequent breakdown, which in turn decrease reeling efficiency. The reeling velocity has to be controlled so that the total working period of repairing any breakdowns may be less than 60 percent of one pulse operation period. The breakdown ratio by snap reading is about 1.5 percent to under 2 percent
- Arrangement of reeling part – Disordered reeling parts make reeling difficult, reducing the raw silk percentage and the reeling efficiency while deteriorating the raw silk quality. Reeling conditions of reeled cocoons should be monitored through continuous inspection.
- Quality control during raw silk reeling – The purpose of the reeling process is not only to raise the raw silk yield of cocoons and reeling efficiency but also to improve raw silk quality.
- Size development and evenness – To maintain reeling thread in the required size, the average cocoon number per thread must be adjusted by a check to produce silk thread in the same size throughout all ends during reeling. If the size is different from the required size it should be readjusted by the group size controller. This will reduce size deviation. By improving the accuracy of cocoon supplying each silk thread becomes uniform in size and different skein sizes are reduced. It can also improve the size deviation and evenness of raw silk quality through the accuracy of cocoon supplying work and the improvement of cocoon reliability.
- Defects – Defects in raw silk are divided into super major defects, major defects, and neatness defects. Defects occur based on reeling conditions. Types of defects and remedies are explained in Cohesion – Good cohesion raw silk is needed for the warp of silk fabric. Factors that improve the cohesion are temperature, amount of reeling tension, sufficient
croissureand good drying of raw silk.
- Colour – The water consistency and temperature of groping end part and reeling part affect the color of raw silk. Therefore, the temperature control and water supply in the reeling machine should be constantly monitored to obtain a uniform color of raw silk.
6. SILK THROWING:
When the raw silk arrives at the manufacturing center, it is in the form of a continuous strand in which the individual filaments are cemented together by the sericin. Silk may for many purposes by woven without further preparation by woven without further preparation. Usually, the raw silk as received from the primary market is soaked in an oil or soap emulsion to soften the thread without however dissolving the silk gum. It is then wound on bobbins and two or three (several strands) of these multifilament strands are doubled and twisted together to form the desired heavier size of the yarn. This process of doubling in the cotton system is known as “Throwing”. The “Throwster” simply converts the raw silk thread into a yarn od proper size for manufacturing or by regulating the twist produces various qualities of silk yarn for the several purposes required for the weaving or knitting of various kinds of fabrics. The term “Throwing” is apparently derived from an anglo–saxon word. “Thrown word meaning to whirl or spin. And the word in this connection means to twist the silk. Silk requires especially skill and knowledge as well as expensive machinery and consequently, it has developed into a separate and districts business. Degumming: The natural gum, sericin is normally left on the silk during reeling throwing and weaving. It acts as a size which protects the fiber from mechanical injury. The gum is removed from the finished yarns or fabrics, usually by boiling with soap and water. Silk Fabrics woven with the
TYPES OF THROWN SILK YARN:
Physical Properties of Silk Fabrics:
- Thickness: 12 to 25 micrometers
- Thickness: 12 to 25 micrometers
- Color: whitish, yellowish or greenish
- Length: 10 to 250 mm
- Density : 1.25 g/cc
- Tenacity: 25 to 40 CN/tex
- Moisture regain : 11% (at 65% R.H and 20°C)
- Elongation : 15 to 20% (dry) , 25 to 30% (wet)
- Flame reaction: partial burning, the odor of burnt horn
Composition: The silk fiber is chiefly composed of 80% of fibroin, which is protein in nature and 20% of sericin, which is otherwise called as silk gum. Strength: Silk as a fiber, has good tensile strength, which allows it to withstand great pulling pressure. Silk is the strongest natural fiber and has moderate abrasion resistance. The strength of the thrown yarns is mainly due to the continuous length of the fiber. Spun silk yarn though strong is weaker than thrown silk filament yarns. Elasticity: Silk fiber is an elastic fiber and may be stretched from 1/7 to 1/5 of its original length before breaking. It tends to return to its original size but gradually loses little of its elasticity. This would mean that the fabric would be less sagging and less binding resulting in the wearer’s comfort. Resilience: Silk fabrics retain their shape and have moderate resistance to wrinkling. Fabrics that are made from short – staple spun silk have less resilience. Drapability: Silk has a liability and suppleness that, aided by its elasticity and resilience, gives it excellent drapability. Heat Conductivity: Silk is a protein fiber and is a non-conductor of heat similar to that of wool. This makes silk suitable for winter apparel. Absorbency: Silk fabrics being protein in nature have good absorbency. The absorptive capacity of the silk fabric makes comfortable apparel even for the warmer atmosphere. Fabrics made from silk are comfortable in the summer and warm in the winter. Silk fiber can generally absorb about 11 percent of its weight in moisture, but the range varies from 10 percent to as much as 30 percent. This property is also a major factor in silk’s ability to be printed and dyed easily. Cleanliness and Washability: Silk fabric does not attract dirt because of its smooth surface. The dirt, which gathers can be easily removed by washing or dry cleaning. It is often recommended for the silk garments to be dry-cleaned. Silk fabrics should always be washed with a mild soap and strong agitation in the washing machine should be avoided. Silk water – spot easily, but subsequent washing or dry cleaning will restore the appearance of the fabric. Specific Gravity: Degummed silk is very fewer dens than cotton, flax, rayon or wool. It has a specific gravity of 1.25. Effects of Moisture: Like wool, silk absorbs moisture readily. It can take a third of its weight of water without feeling wet to touch. Silk has regained of 11.0%. Degummed silk swell as it takes up moisture. At 100 % relative humidity silk absorbs 35% of its weight of water and increase in cross-sectional area by 46%.