SILK

WE ARE SPECIALIZED

SILK FIBRES
Silk is usually referred to as the queen of the fiber. Like wool, silk is also an animal fiber. But instead of being grown as hair, it is produced by insects as a handy material with which they build their webs, cocoons, and ropes. Almost the entire commercial silk industry based on one insect – named as the silkworm. In spite of its name, the silkworm is not really a worm. The silk is made by silkworm when it wants to change into a chrysalis and then a month. It spins the silk and wraps the fiber around itself in the form of cocoon inside which it can settle down its comfort. For 3000 years China held a monopoly in the silk industry. It was first produced in China as early as the Neolithic period. Japan and Korea are also has a good name in silk Industry. Between the Ganges and the Brahmaputra, soon became established. From India, sericulture moved again to west in Persia and the countries of the Mediterranean. Nowadays, Sericulture has become an important cottage industry in countries such as Brazil, China, France, India, Italy, Japan, Korea, and Russia. Today, China and India are the two main producers, with more than 60% of the world’s annual production.
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
Cultivation of Silk Worms / Cocoons (Sericulture) ↓ Hatching ↓ Molting ↓ The spinning of the cocoons ↓ Silk Reeling ↓ Silk Throwing
PRODUCTION AND PROCESSING OF SILK:
Silk Fabric Silk is a natural protein fiber produced by certain caterpillars in order to encase themselves in the form of cocoons. The making of silk is different from that of other natural fibers. There are many steps involved in silk manufacturing:
1. CULTIVATION OF SILK WORMS / COCOONS ( SERICULTURE)
It is the cultivation of cocoons for their filaments. Although there are several commercial species of silkworms, the best raw silk is obtained from the species of moth called Bombyxmori. (The caterpillar of the domesticated silk moth) is the most widely used and intensively studied silkworm. Firstly the eggs are being laid by the silk moth, which sticks to the paper of the egg sheet by virtue of its gummy substance in-closed in them. They change their color rapidly to a bluish, brown or black shade. After the elimination of disease, sheets are kept or stored in cold storage for a period of hibernation of 6 to 10 months. Rearing of the silkworms starts as soon as leaves begin to appear on the mulberry trees. i.e. When the mulberry starts budding at the same time the sheets of the eggs are warmed up to encourage them to begin hatching. In large, scientifically run farms warming is done artificially. The required egg sheets are placed in an incubator where the temperature is closely regulated at 80 degree Celsius for the period of incubation of about 10 days. But where silk is a part of the present economy like some regions of China, the eggs are warmed by the contact with the human body. Breeding of silkworm occurs once in a year but under scientific conditions, they may be hatched three times a year. The female moth lays around 350 to 400 eggs and the moths die soon after. As they are subject to hereditary infection, the eggs from infected moths are destroyed which results into production of fine silk. Larvae of about 3mm are hatched from the eggs. For about 20 to 30 days, they are carefully nurtured and are fed five times a day on chopped mulberry leaves. In the meantime, the larvae change their skin four times and are formed into caterpillar of about 9 cm long. Now they are ready to spin a cocoon for which racks, clusters of twigs or straw are provided. The caterpillar has small openings under their jaws called spinnerets through which they secrete a protein like substance. This substance solidifies when it comes in contact with air and the filament thus formed is spun around the silkworm in the figure resembling the digit 8. In three days the cocoon gets completed which is about a peanut shell’s size. The filament is held together by sericin or silk gum. The life of the worm is ended by the process of ‘stoving’ or ‘stifling’ in which the cocoons are heated. Some of the cocoons are preserved so that the pupa or chrysalis developed them into moths for further breeding.
2.HATCHING:
  1. 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.
3. MOLTING:

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:

 

# Japanese Central China Canton
Incubation 12 10 8
Stage 1 6 6 3
Stage 2 5 4 3
Stage 3 6 5 3
Stage 4 6 5 3
Stage 5 7 5 4
Spinning Cocoon 5 5 1
Chrysalis 12 11 10
Moth 4 3 1
Total 63 54 36
4. THE SPINNING OF THE COCOONS :
A careful dissection of the body of the caterpillars shows two large glands wherein the silk secretion is formed i.e. the liquid silk contained in these glads inside the silkworm. From these two glands, it flows in two channels to a common exist tube called the spinneret in the silkworm head, to produce the fibroin. At this point, the flow is joined by secretion of two others – symmetrically located glands, which produce the silk glue or sericin that comment together with the two filaments of fibroin. So as the liquid silk emerges out it hardness into very fine filament and these are coated and stuck together by a gummy substance called sericin. This comes from two other glands nearby. The silk used by the worm there for is really a two filament held together as a single strand by the sericin cement. Hence the fully developed or ‘ripe’ worms are taken from their feeding trays and are placed on spinning racks or straw mounting. So they may find a charge for their silk filaments. Working on the inside, each worm builds on oval casing or shade by extruding through its spinneret the various fluid from its silk glands. As the silk excludes the silkworms moves its heads backward and forwards in a figure and movement layer after layer is added by moving its head a to describe arcs of circles crossing in fibers. Gradually, it surrounds itself with a strongly built cocoon which serves as a protective covering made from a continuous silk strand that may be up to a mile in length. Spinning usually takes 2 or 4 days during which time the silkworm has shrunk to a mere vestige of its original bloated body. After spinning its cocoon the enclosed silkworms undergoes a remarkable transformation passes from the form of a caterpillar into a chrysalis or pupa. The coating of the chrysalis is hard and yellow to brown. It appears without life but it is sensitive to touch. It rapidly develops into a moth. On the silk farm, the chrysalis must be killed before it happens. For the moth cuts the cocoon by secreting a fluid that dissolves away a section of a cocoon to make a hole and through this whole, the moth escapes from the cocoon. The continuous silk filament is thus broken up into thousands of short pieces which are useless of reeling. Within a few days of making its cocoon, the chrysalis is killed by heating or stiffing. It is baked in the sun or in an oven or stuffed in hot air or steam. The cocoon can then be kept indefinitely without damage for reeling. The moth is whitish grey, has a soft body and rudimentary wings. It has no moth and therefore does not eat. The female is larger than the male. But both are unable to fly. The entire short moth life of 1 to 4 days is for reproduction. After making the mother moth lays about 500 eggs which complete her life.
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:

 

 

  1. 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.
  2. 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.
  3. GRASSERIE: Grasserie is a virus disease and is caused by the mismanagement of the worms at moulting periods 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.
  4. 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.
  5. 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.

 

 

  1. 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.
  2. 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).
  3. 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.
  4. 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 sericine is 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 croissure 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.
AUTOMATIC REELING MACHINE
In raw silk production, the continuing increase in labor costs has mandated automation. Around 1950, the Automatic reeling machine, which controls the number of reeling cocoons per thread, was invented. Shortly thereafter, it was replaced by a second Automatic reeling machine, which could automatically control the size of the reeling thread. The Automatic reeling machine mechanizes the processes of groping ends, picking ends; cocoon feeding to reeling thread and separation of dropped end cocoons during the reeling process. The efficiency of the Automatic reeling machine compares favorably with the manual Mult-ends reeling machine. The Automatic reeling machine though built to replace manual reeling, still requires manpower for problems with the reeling thread, which must be corrected by hand. A moderate amount of cooked cocoons are carried to the newly cooked cocoon feeder (3) and then removed into the groping end part (4). The end groped cocoons go to the picking end part (5) and the correctly picked end cocoons are dispensed to the cocoon supplying basket (8) which continuously rotates around the reeling basin on an endless chain belt. Usually, the reeling method is classified into the fixed cocoon feeding system and moving cocoon-feeding system. In the case of the fixed cocoon feeding system, the correctly picked end cocoons in the rotating cocoon baskets are poured into the arranging basin (11) and here the picked end of each cocoon is hung on the end holding reel (7). When the size detector of the reeling thread indicates the feeding of cocoons, the picked end cocoons on standby are fed to the reeling thread by a feeding spoon. The reeling thread fed by picked end cocoons passes through the jetboute (23), silk button, first guide, second guider, third guide, fourth guider, denier indicator (5’), fifth guider and traverser (3’), and then it is finally wound onto small reels (1’). The end dropped cocoons are placed into the cocoon flowing tunnel by the remover plate. They are carried into the pupa separating drum (14). However, more reliable cocoons are poured into the end groping part (4) by the conveyor belt (15) and reels-finished cocoons are placed into the dropped-pupa case (17) for parchment layer cocoons (Figures 13 and 14).In the case of the moving cocoon feeding systems, the correctly picked end cocoons are contained in the moving cocoon basket equipped with cocoon feeding apparatus. They are fed by the feeding fork of the cocoon basket, which moves simultaneously around the reeling basin. The denier indicator of the reeling thread indicates the feeding motion of the cocoon. After cocoon feeding, the reeling path of the moving cocoon feeding system is the same as that of the fixed cocoon feeding system. Generally, one set of the Automatic reeling machines has 400 ends, while one basin has 20 ends. The operating efficiency of the Automatic reeling machine is easily affected by cocoon qualities, drying and cooking machinery and quality of reeling water.
BRUSHING AND PICKING SECTION –
An automatic ten-brush unit brushes cocoons with independent arms rotating in reverse motion on an axis in circular basins. Picking frames rotating in one direction pick off the brushed cocoon filaments when a cam during the operation raises the brushes. Selective picking is completed in the most effective manner by this equipment. To maintain the exact number of cocoons at each reeling end, a control device is attached which detects the amount of cocoons in the cocoon suppliers and automatically supplements deficiencies in the number of cocoons.
REELING SECTION –
The denier indicating and detecting a device. In these devices, the yarn constantly passes through the denier indicator and detector, which are set to a given size. The size of the thread being reeled is detected through the balance between the friction of the running thread and an eccentric weight fitted on the denier indicator. When the thread becomes thinner than the fixed limit, the denier indicator indicates the necessity of feeding-ends. This indicator is composed of two gauge glass plates with other pieces of gauge plate which have a slit between them corresponding to the given size of thread to be reeled. The size of yarn may be adjusted to the required sizes by varying the irregular weight with the denier-adjusting device; if a wider range of adjustment is required the denier indicators have to be replaced. – A conveyor system for cocoon suppliersThe fixed end feeding system is employed together with a conveyor system to carry cocoon supplies and feed cocoons to the reeling section whenever required. – End feeding for cocoons suppliersCocoons is supplied to the conveyor, which rotates constantly around the reeling section. The feeding lever fixed to the detecting mechanism will trigger the driving lever on the cocoon supplier only when the size of yarn becomes thinner than the required denier during reeling operation. – Stop motion there is a defect in the reeling, the reel is automatically stopped by a break, which is activated by contact pressure from operation of the detector level. – Dropped cocoon gatherersThe apparatus gathers baskets that have collected all cocoons dropped during end feeding. These are carried to the dropped cocoon separator. These baskets travel intermittently between the cocoon suppliers. – The separator of dropped cocoons The device accurately distinguishes and separates pupae dropped middle layer cocoons and thick layer dropped cocoons.
SEMI-AUTOMATIC REELING MACHINE –
This is a mixed-mode or hybrid machine between the automatic and multi-ends reeling machines. As an application, this type is better for improved reeling efficiency and raw silk quality than the multi-ends reeling machine. The semiautomatic reeling machine can be operated with poor quality cocoons but relies on more labor than the automatic reeling machine. The cooked cocoons are carried into the groping end part (10) and the end-groped cocoons are removed to the picking end part (11). The correctly picked end cocoons go through the cocoon supplying basket (9) and then to the arranging basin (8). When the size detector of the reeling thread indicates the feeding motion, the picked end cocoons on standby are fed to the reeling thread by a feeding spoon. The reeling thread passes through the jetboat, silk button, first guide, second guider, third guide, fourth guide, size detector, fifth guide, and traverse guide, and then it is finally wound onto small reels (4). The end dropped cocoons are collected by the cocoon buckets (13) and removed to the cropped cocoon basin, where more reliable cocoons are separated and then poured into the groping end part (10). The principal difference between a semi-automatic reeling machine and an automatic reeling machine is that the cocoon end groping, cocoon end picking and cocoon carrying are manual.
A) REELING VELOCITY (R.V.)
Reeling velocity is defined as the winding speed of raw silk on the reel. The reeling velocity is measured as the length of raw silk reeled during 1 minute or as the revolution number of the reel per minute. It is usually calculated by the following formulas.
B). GROPING ENDS
The high water temperature of the groping ends section dissolves sericin to a great extent and improves the reliability of the cocoon. However, it is apt to reduce the raw silk percentage of the cocoon. Alternatively, the too low water temperature in this process can reduce the groping end efficiency, the reliability percentage, and the reeling efficiency.
C). PICKING ENDS
This is a very important function of the reeling operation, which can affect raw silk percentage and reliability. Correct end cocoons should not be permitted in picking ends to minimize cocoon filament waste. Insufficient picking ends causes the feeding of incorrect end cocoons, breaking down of the reeling thread, and affects the accuracy of the feeding end work. On the other hand, excessive picking ends reduce raw silk by causing an increase in waste. The picking end with too many cocoons can cause the work to be carried out inaccurately and is apt to increase waste of cocoon filament by repeated work on correct end cocoons. The number of cocoons for a picking end section should be below 40 pcs, and the recommended temperature of the water bath is 40 to 50° C. In automatic end-picking machines, the degree of end picking varies between 80 to 85 percent for good cocoons, 75 to 80 percent for medium ones and 70 to 75 percent for inferior ones.
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 croissure and 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 sercian still on the yarn have a characteristic, stiffness of handle. They are also dull in appearance. After degumming the silk acquire its beautiful luster. As much as one-third of the weight of the fabric may be lost when the gum is removed in this way. Raw silk with the gum still on the filaments is called hard silk. Degummed silk is soft silk. Hard Silk: Foulard fabric, Georgette, Chiffon, crepe de chine are hard silk which is afterward degummed.

TYPES OF THROWN SILK YARN:
There is the number of the different type if thrown yarn which is described by the manufacturer as follows: TRAM: This is lightly twisted thread formed by twisting 2 or 3 strands of silk together. Low twist tram will have only 2-3 twist per inch and high twist tram may have 12-20 twists per inch. ORGANZINE: This is very strong yarn made from high-quality silk. Two or three more strands are twisted separately and the compound thread then twisted together in the opposite direction from about 9-30 TPI. Organzine is used mainly as warp in woven fabric. CREPE: These are the yarns with a very high twist, as many as 30-70 TPI. They are used for crepe and chiffon fabrics in woven and knitting. GEORGETTE: It is composed of two or three untwisted singles doubled and twisted up to 7-75 turns right and left and used as filling yarn in weaving. COMPAZINE: This yarn is made from two tightly twisted yarn (Crepe Yarns) and one untwisted yarn. When these are twisted together about 5 turns per inch. The untwisted yarn crinkles up and giving the ‘knobby’ appearance characteristics of crepe thread. This also gives a balanced yarn which will not kink in Knitting. SEWING: These are tightly twisted strong yarns. They are made by twisting 2-3 silk strands together and then combining several of the resulting threads by twisting in the opposite direction. [Usually 10-50 raw silk threads of 14 denier size formed in 2-3 ply]. In sewing thread, the criterion of strength is given by the products of yarn per ounce and breaking strength in ponds. The minimum standard for this product is 6000. EMBROIDERY SILK: Embroider silk are often simple untwisted strands united by a slight twist. Charmeuse The silk we have in mind when we think of ‘traditional’ silk. The front of the fabric is in a shimmery satin weave. The back of the fabric is a flattened crêpe. BENEFITS Charmeuse has more drape than crêpe de chine and works well for scarves, blouses and lingerie. Chiffon A light, matt fabric made from fine twisted yarns, spaced out to make the fabric transparent. Dimension is added to garments by the creation of billows of fabric. Unless it is used for scarves, garments with chiffon normally require lining or backing. Crêpe de Chine A lightweight fabric made by fibers, where part of them are twisted clockwise and others in a counter-clockwise direction. These fibers are then woven in a plain-weave fabric. The twisted fibers give crêpe its distinctive ‘pebbly’ look and feel. Comes in many different varieties – crêpe de Chine, Moroccan crêpe and crêpe georgette… Dupion Silk Produced from two silkworms that spin a cocoon together. This makes a strong double-thread silk, usually resulting in a rough yarn and irregularity in sheerness or weight. Feels coarse. Black specks which occasionally appear in the fabric are part of the original cocoon of the silkworm. Removing them would both weaken the fabric and destroy part of its beauty and character. They are inherent to dupion silk fabric and should not be considered as defects in weaving. BENEFITS Strong and lustrous Fuji Silk Medium-weight fabric, woven from spun silk fibers. Have a soft luster and a lavish feel, reminiscent of high-quality suede. Has a fluid drape. BENEFITS Durable. Resists wrinkles. Habotai Silk Is Also known as China silk, Habutai, Pongee. The “classic” silk fabric. Was first used to line kimonos. Plain-weave fabric. Its weight can range from 5 mm to the heavier 12 mm. Most scarves are made of 8mm Habotai. BENEFITS Soft and lightweight. Habotai silk is a sheer fabric and has a graceful drape and smooth surface. Great for scarves. Noil Silk Known as ‘raw silk’. Made from the short fibers left after combing and carding, so it doesn’t shine like many other silk fabrics. Very versatile fabric. Has a matte surface and rough finish – has a ‘nubby’ feel. Doesn’t show pin holes. Off-white in color. It is easily distinguished from other types of silk for the subtle flecks on it, which are natural particles of the cocoon. BENEFITS Looks similar to cotton, but still feels soft against the skin. Drapes better than cotton and resists wrinkling. Durable. Easy to care for. Great for traveling. Tussah Silk Also known as ‘shantung’. A type of wild silk, that is produced by silkworms that feed on oak and juniper leaves. As the worm is not grown in a controlled environment, the moth hatches from the cocoon and interrupts the filament length, resulting in short and coarse fibers, instead of long and lustrous ones. Usually comes from India or China. India silk generally has more luster to it. Feels coarse and is delicate and stiff. Difficult to dye and most often available in its natural color, a creamy tan. BENEFITS Both lightweight and airy, as well as dressy, giving cool comfort to the wearer. Does not wrinkle easily. Good for traveling. Silk Cashmere A blend of the two luxury fabrics – pure silk and the fine wool that comes from the undercoat of the cashmere goat. The natural crimp it contains aids the fiber to interlock during processing. This enables it to be spun into a very fine and lightweight fabric. The number of crimp correlates with the fineness of the spun yarn and the softness of the finished product. The fabric retains the small air spaces trapped between fibers which makes it warm without being heavy. BENEFITS Luxuriously soft and lightweight with good insulation quality. Extremely warm. Does not scratch like other wool. Silk Cotton Difficult to weave together in order to keep the separate fibers from unraveling. As warm as silk, but of a heavier weight. Thicker than silk on its own. BENEFITS Durable. Has a superior substance and body to plain cotton. Less slippery than silk due to its heavier weight. Silk Linen Used to create finer fashions and premium apparel. BENEFITS Much like our other silk mixes, the feel and drape of pure cotton linen is improved when blended with pure silk. Silk Wool Pure wool on its own does not necessarily feel wonderful against your skin, but blending it with silk will create such a fabric. Patra uses Merino wool in its garments, the finest sheep wool fabric in the world, famed for its superior shine and softness. Merino wool has natural elasticity. BENEFITS The addition of Merino wool means that this mix has the maximum absorbent quality and has great breathability. It absorbs moisture and transfers it to the air, creating a dry layer next to the skin, as well as absorbing odors from the body. Resistant to dirt and wrinkling. Has the ability to hold dye. Provides warmth without adding weight. Non-scratchy wool. Has a higher level of UV light protection.

 

 

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%.

CHEMICAL PROPERTIES OF SILK FABRICS
Silk is slowly attacked by acids but is damaged readily by basic solutions. Strong oxidizing agents such as hypochlorite rapidly discolor and dissolve silk, whereas reducing agents have little effect except under extreme conditions. Silk is resistant to attack by biological agents but yellows and loses strength rapidly in sunlight. Silk is often weighted with tin and other metal salts. These salts make silk even more sensitive to 1ight-induced oxidative attack. Silk undergoes charring and oxidative decomposition when heated above 175°C in the air over a prolonged period of time. Reaction to Bleaches: Silk, like wool, is deteriorated with chlorine bleaches like sodium hypochlorite. However, mild bleach of hydrogen peroxide or sodium perborate may be used for silk. Shrinkage: Silk fabrics are subjected only to normal shrinkage which can be restored by ironing. Crepe effect fabrics shrink considerably in washing, but careful ironing with a moderately hot iron will restore the fabric to its original size. Effect of Heat: Silk is sensitive to heat and begins to decompose at 330° F (165° C). The silk fabrics thus have to be ironed when damp. Effect of Light: Silk fabric weakens on exposure to sunlight. Raw silks are more resistant to light than degummed silk. Resistance to Mildew: Silks will not mildew unless left for some time in a damp state or under the extreme conditions of tropical dampness. Resistance to Insects: Silk may be attacked by the larvae or clothe moths or carpet beetles. Reaction to Alkalis: Silk is not as sensitive as wool to alkalis, but it can be damaged if the concentration and the temperature are high. A mild soap or detergent in lukewarm water is thus advisable. Reaction to Acids: Concentrated mineral acids will dissolve silk faster than wool. Organic acids do not harm silk. Affinity for Dyes: Silk has good absorbency and thus has good affinity for dyes. Dyed silk is colorfast under most conditions, but its resistance to light is unsatisfactory. Resistance to Perspiration: Perspiration and sunlight weaken and yellows silk fabrics. The silk itself deteriorates and the color is affected causing staining. Garments worn next to the skin should be washed or otherwise cleaned after each wearing.
CHARACTERISTICS OF SILK:
High wet strength Good moisture regain Soft feel Good lustier Expensive cleaning Sensitive to cleaning & washing Sensitive to the sun and heat Poor wrinkle and abrasion resistance
USES OF SILK:
The bulk of silk fibers produced is utilized in preparing silk clothes. Uses of pure silk are decreasing gradually due to its high-cost value and costly maintenance. Production of synthetic fibers has posed a serious threat to the silk industry. Clothes in which Silk fibers are combined with other natural and synthetic fibers are in great demand not only in India but also in foreign countries. Seeing this demand many textile industries are manufacturing clothes like Teri-silk, cot silk etc. Besides silk being used as garments, it is also used in other industries and for military purposes. It is used in the manufacture of fishing fibers, parachutes, cartridge bags, insulation coils for telephones and wireless receivers, tires of racing cars, filter clothes for flour mills, and in medical dressings and suture materials. Insulation coils for telephones and wireless receivers, tires of racing cars, filter clothes for flour mills, and in medical dressings and suture materials.
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