Raw Silk Manufacture (Reeling)

Introduction

The process of drawing silk fibre from the cocoon is called ‘reeling’. The cocoons are cooked in hot water and the silk fibre is unwound from the cocoons. The silk consists of two proteins, the inner core of fibroin and an outer cover of gum sericin. During reeling, the cocoons are processed in hot water at 95-97⁰C for 10-15 minutes. This process is called cooking. This cooking will enable the sericin portion to get softened and make unwinding easy without breaks. The cocoons after cooking are reeled in hot water in different types of machines. In India, 61% of the silk amounting to 1,320 tonnes is reeled on the country-type charka (spinning-wheel) numbering 6,656. The silk produced with the country charka is of very poor quality, as the thread is not uniform, as it carries many slubs etc. the improved cottage-type basins have been introduced recently into India. Provision for button-holes and a proper croisure system to maintain the thickness of the fibre, and to control the defects of neatness in the cottage basin have facilitated the production of better-quality silk. As much as 4,000 cottage basins in the country produce 806 tonnes of silk.

Large-scale basins organized scientifically are arranged in filatures for the extraction of superior-quality fibre. The silk produced by the filatures is superior because of the low level of defects of cleanliness and uniformity in the thickness of the fibre. Only 8% of the total production of silk in India is contributed by filatures.

The silk produced from multivoltine races of silk worms is poor in quality and is known to have greater defects, such as lousiness, and defects in neatness and cleanliness and is of very poor quality in light of the international D grade. The silk produced by the bivoltine races of silkworms possesses superior neatness and cleanliness, is without lousiness and has high tensile strength and stands to the international A grade.

The new technology of handling silkworms in the country has shown that bivoltine silkworms, producing the international quality of silk, can be produced throughout the year in the Karnataka state in India. It has been shown that, on an average, 30 to 35 kg of cocoons, yielding 3 to 4 kg of high-grade silk can be produced by rearing 40,000 eggs of bivoltines, as compared with 25 kg of cocoons and 1.4 kg of low-quantity fibre from multivoltines.

• Water

The water used in silk reeling plays an important role. It is estimated that to produce one kg. Of silk from charka, the volume of water required is about 100 liters. If the quality of water is poor, the impurities suspended in the water will adhere to the silk thereby the colour, and lustre of silk would be influenced. The water used for cooking cocoons should be colour less, odour less and transparent. The pH of water should be between 6.8 to 8.4.

• Cocoon drying

The cocoons contain live pupae which will emerge out with in 10-12 days of cocooning hence, cocoons ae stifled. Once the moth emerge out, the shell becomes of no use to reel since the adult emerges out by piercing the cocoon shell. The cocoons contain live pupae, which will emerge out with in 10-12 days of cocooning hence, cocoons are stifled. Once the month emergesout, the shell becomes of no use to reel since the adult emerges out by piercing the cocoon shell. The primary object of drying cocoons is to kill the pupae and to reduce the water content of fresh cocoons.

1. Sun drying

The freshly harvested cocoons are directly exposed to sunlight. In this method the harvested cocoons are spread in one layer and directly exposed to bright sun-light for several days from morning to evening until the pupae inside is killed and cocoon is found properly dried. This can be identified by shaking the cocoon which will make rattling sound.

Advantages:

1. this is cheapest method of stifling

2. Easily available method of cocoons drying to rearers.

3. These cocoons can be reeled immediately.

Disadvantages:

1. Continuous exposure to hot sun-light, damages the silk quality due to the action of ultra violet rays.

2. Some times continuous sun-light may not be possible, particularly during rainy season. Partial drying of cocoons will spoil the quality of silk.

3. Wastage of silk during reeling will be more.

1. Steam stifling

Methods

• Steam stifling is the very common and easy method.

• The fresh cocoons are directly exposed to hot wet steam.

• Basket steaming

• Barel steaming

• Chamber steaming

Advantages

1. conveniently used to stifle large quantities of cocoons

2. uniform stifling of cocoons

Disadvantages

1. steam stifled cocoons cannot be reeled immediately, other wise the sericin will wet and fibroin comes is lumps while reeling

2. in steam stifling pupa is killed inside and does not dry it.

1. Hot air conditioning

In the modified hot air conditioning chamber there are five compartments. Each chamber is different ranges of temperature.

• The first chamber is filled with cocoons are supplied of with hot air at 50⁰C for about 3hrs.

• The second chamber by sliding mechanism by pulling out where 70⁰C for about 3hrs.

• The third chamber cocoons are dropped into 75-80⁰C.

• The forth chamber is cocoons dried by hot air at 80-90⁰C temperature

• The fifth chambers are gradually exposed to hot air in the 12 hours of time and continuous process.

Advantages

1. Any amount of cocoons can be easily stifled.

2. Time saving, labour saving.

Disadvantages

1. Cocoons of uniform size are quite suitable for this process, but Indian multi-voltine cocoons with different sizes and different qualities need different degrees of temperature for stifling.

2. Costly and skilled labours are required.

Storage of cocoons

While storing the cocoons certain precautions should be taken into consideration other wise improper storage of cocoons leads to loss due to occurance of damage to the cocoons.

Preventive measures should be taken:-

1. avoid storage of stained cocoons

2. storage room should have good ventilation.

3. Cocoon storage place should be clean and dry. No waste cocoons should be stored in the premises.

4. Always ensure proper drainage of cocoons before storage.

5. Relative humidity in the storage room should not exceed 70%.

6. Before storage of cocoons, the storage place should be thoroughly disinfected.

7. In case of long storage of cocoons, frequent turnings should be given.

Sorting

Sorting of cocoons is already done at once, once again it should be checked prior to reeling.

Deflossing

Floss is the outer most layer of cocoon which is only a protective covering and is not reelable. Prior to reeling floss has to be removed by any of the methods to avoid obstruction during reeling.

Cocoon ridding

After deflossing the cocoons, in the process of ridding, cocoons are separated according to their sizes by simple sieves into big, small and medium size cocoons and collected in separate containers. This will facilitate the reeling operations easy.

Definition

Reeling is a process of unwinding of silk filament from the cocoon. Reeling process is an important activity. Depending upon the required thickness (denier) of silk thread filaments from number of cocoons are combined together and reeled. An efficient reeler will maintain the fixed number of cocoons per end to produce uniform denier silk. Reeling is carried out by distinctive methods.

• Charka

It is about 50% of total raw silk production is contributed by charka. Reeling machine is traditionally home built by using wooden material with the assistance of black smith and corpenter hence,

1. Investment on reeling machinery is very-very less.

2. Even the inferior quality cocoons can be also reeled by charka.

3. No much technology is involved in this system of reeling.

4. Only one reeler can reel.

5. Brushing and cooking are done in the same basin.

6. The cost of production is very low compared to other reeling machines.

7. Involvement of labour is very less only two persons are sufficient to maintain.

8. Reeler can establish a charka unit at the back yord of his own residence.

9. Production per day would be around 1 kg from each charka.

10. Marketing of charka reeled silk is very easy and it will be always at his door steps.

In charka, there are three distinct parts.

1. Mud-Platform

2. Distributor

3. Reel.

Important points

1. The reel should be always smooth.

2. As the cooking and brushing, reeling are done in the same water. The water should be changed frequently.

3. As the cooking and brushing, reeling are done in the same water.

4. After cooking the cocoons thoroughly, when reeling ends are found, the temperature of water in the reeling basin should be lowered to 40 0C by adding cold water.

Disadvantages

1. The silk produced by charka reeling is inferior quality.

2. As the reeling is done in water at very high temperature which is harmful to the reeler.

3. Frequently, water is to be changed and heated again, this will increase the fuel cost.

• Cottage Basin

In cottage basin, the cocoons are cooked separately and re-reeling is done separately to increase the quality of silk. In cottage basin cooking is done separately and the reeling basins are fixed to a reel bench. There will be 6-10 ends in each basin. Arrangement to supply hot water to each basin and to drain out the dirt water accumulated due to floss and sericin is made.

Advantage

1. Quality of silk produced is superior to charka silk.

2. Water in the reeling basin will be fresh. This will help to maintain the quality of silk.

3. Production per day can be increased, as it is power operated.

Points to be remembered by reeler

1. The waste material stuck to the jetteabout should be removed from time to time.

2. It is acvisable to take a mixture of fresh and partially reeled cocoons while reeling.

3. Replace the water in the reeling basin from time to time.

4. Apply the lubricant to croissure pulleys for smooth running.

• Filature

Filature or multi-end reeling machine works on the principle of slow motion reeling and thread production on small reels at a large number of ends per basin.

Advantages

1. Superior quality silk can be produced

2. Wastage is reduced

3. High productivity

4. Less labour

5. Arrangements are made to control the speed of the reels and tension of the threads.

6. Raw silk per day will be around 800 gms of superior quality.

• Automatic reeling machine

Bi-voltine cocoons are best suited to automatic reeling machines. This machinery requires superior quality cocoons and uniform size of cocoons with less floss. Generally the multi-voltine cocoons are not fit for automatic reeling. This is particularly due to inferior quality. The silk produced from automatic reeling machine will be superior.

Ag.
Technologies
(Sericulture)