Sericulture: Raw Silk

Sericulture, or silk farming, is the rearing of silkworms for the production of raw silk. Although there are several commercial species of silkworms, Bombyx mori is the most widely used and intensively studied. According to Confucian texts, the discovery of silk production byB. mori dates to about 2700 BC, although archaeological records point to silk cultivation as early as the Yangshao period (5000 – 3000 BCE).[1] About the first half of the 1st century AD it had reached ancient Khotan,[2] and by AD 140 the practice had been established in India.[3] Later it was introduced to Europe, the Mediterranean and other Asiatic countries. Sericulture has become one of the most important cottage industries in a number of countries like China, Japan, India, Korea, Brazil, Russia, Italy and France. Today, China and India are the two main producers, together manufacturing more than 60% of the world production each year.

Production
Silkworm larvae are fed mulberry leaves, and, after the fourth moult, climb a twig placed near them and spin their silken cocoons. This process is achieved by the worm through a dense fluid secreted from its gland structural glands, resulting in the fibre of the cocoon. The silk is a continuous-filament fiber consisting of fibroin protein, secreted from two salivary glands in the head of each larva, and a gum called sericin, which cements the two filaments together. The sericin is removed by placing the cocoons in hot water, which frees the silk filaments and readies them for reeling. The immersion in hot water also kills the silkworm pupae. This is known as the degumming process.[4] Single filaments are combined to form thread. This thread is drawn under tension through several guides and wound onto reels. The threads may be plied together to form yarn. After drying the raw silk is packed according to quality. [edit]Stages of production

The stages of production are as follows:
1. The silk moth lays eggs.
2. The eggs hatch, and the larvae feed on the mulberry leaves.
3. When the silkworms are about 10,000 times heavier than when they hatched, they are now ready to spin a silk cocoon.
4. The silk is produced in two glands in the silkworm’s head and then forced out in liquid form through openings called spinnerets.
5. The silk solidifies when it comes in contact with the air.
6. The silkworm spins approximately 1 mile of filament and completely encloses itself in a cocoon in about two or three days but due to quality restrictions, the amount of usable silk in each cocoon is small. As a result, 5500 silkworms are required to produce 1 kg of silk. 7. The silk is obtained from the undamaged cocoons by brushing the cocoon to find the outside end of the filament. 8. The silk filaments are then wound on a reel. One cocoon contains approximately 1,000 yards of silk filament. The silk at this stage is known as raw silk. One thread consists of up to 48 individual silk filaments. *

third stage of silkworm

silkworms on to Modern Rotary montage

* silk cocoon in mountages
The country of origin of silk is China, since it’s also where most silkworm harvesting occurs. For thousands of years, the Chinese have developed techniques and processes to produce the silk fibres to be sold around the world and adapted into products that people demand. The tradition of raising silkworms and turning their cocoons into raw silk is known as sericulture, a craft that has been perfected and handed down for many generations. Ensuring a high quality silk turnover is a complicated process high quality silk skilled in maintaining a precisely controlled environment (temperature and humidity) for the silk worm, and in growing the mulberry tree that is used as food.

Silk fibres are a continuous protein fibre created from natural processes and extracted from cocoons, which means that these fibres can retain the properties that are associated with the chemicals produced by the silkworm. When secreted by the silkworm, the natural state of the fibre is a single silk thread made up of a double filament of protein material (fibroin) glued together with sericin, an allergenic and gummy substance that is normally extracted during the processing of the silk threads. You can learn more about how silk is made by reading our research paper.

EXTRACTING RAW SILK
The production process of silk can seem deceptively simple but indeed has several steps. In fact, the process of creating silk fibres of the highest quality take a few weeks to complete. Here is a quick breakdown of the entire process:

1. First, the new born larvae of the silkworms are kept in a warm and stable environment and given plenty of mulberry leaves, their favourite diet. 2. The silkworms naturally produce cocoons around themselves to pupate. This process is done through “spinning”: the worm secretes a dense fluid from its gland structural glands, resulting in the fibre of the cocoon. 3. The cocoons are sorted carefully according to size and quality. 4. Boiling water with soap is used unravel the silk fibres from the cocoon. This is known as the degumming process. 5. The outer shell of the cocoon is fed into into the spinning reel, which is still often operated manually 6. The long fibre thread that are extracted from the cocoon are then cleaned and stripped from any deficiencies. 7. The silk fibres are implemented into products such as bedding and clothes. AN EXTREMELY DELICATE PROCESS

The extraction of silk must make sure that only the highest quality cocoons are submitted to the degumming and reeling process. What’s more, the quality of silk generated becomes finer and finer the closer the spinner moves to the inner layers of the cocoon. As the cocoons are exhumed from the boiling water, they become twisted and strands from the edges become to uncling from the rest. These are what eventually results in long fibre Mulberry silk multi-filament. Often, the best quality silk is extracted by the technique of “throwing”, resulting in “thrown silk” which can be made through through knitting or weaving.

SILK FIBRES CAN BE ENHANCED
Did you know that silk is hypo-allergenic purely because of natural properties? However, when it is processed into usable objects that we touch in daily life, it’s also important to make sure that it is not left under the influence of chemicals or other allergens. The process through which a silk duvet is made should be as healthy and clean as the much as the silk production process. What’s more, silk fibres can be made stronger and better through diligent research. Since the silk sleeping environment temperature regulated and moisture absorbent, it’s extremely hard for bacteria to develop. However, most silk fibres cannot be washed safely without the risk of damaging the core structure of the duvet or comforter. This is frustrating, as over the years naturally people might want to clean their duvet. A great example of silk enhancement in action is the application ofnanotechnology to silk fibres in order to add to their natural longevity and strength, and therefore become able to withstand hotter washing temperatures. Sericulture Industry in India

If fashion is a fine art, then silk is its biggest canvas, and if silk is the canvas, then all its weavers, dyers, designers, embroiderers are the greatest artists. Indian silk has enthralled fashion watchers and all categories of consumers across the world with its vast repertoire of motifs, techniques and brilliant hues. India’s traditional and culture bound domestic market and an amazing diversity of silk garments that reflect ‘geographic specificity’ has helped the country to achieve a leading position in silk industry. Present status: India is the second largest producer of raw silk after China and the biggest consumer of raw silk and silk fabrics. An analysis of trends in international silk production suggests that sericulture has better prospects for growth in the developing countries rather than in the advanced countries.

Silk production in temperate countries like Japan, South Korea, USSR etc., is declining steadily not only because of the high cost of labour and heavy industrialization in these countries, but also due to climatic restrictions imposed on mulberry leaf availability that allows only two cocoon crops per annum. Thus, India has a distinct advantage of practicing sericulture all through the year, yielding a stream of about 4 – 6 crops as a result of its tropical climate. In India, sericulture is not only a tradition but also a living culture. It is a farm-based, labour intensive and commercially attractive economic activity falling under the cottage and small-scale sector. It particularly suits rural-based farmers, entrepreneurs and artisans, as it requires low investment but, with potential for relatively higher returns. It provides income and employment to the rural poor especially farmers with small land-holdings and the marginalized and weaker sections of the society. Several socio-economic studies have affirmed that the benefit-cost ratio in sericulture is highest among comparable agricultural crops (Table 1).

Currently, the domestic demand for silk, considering all varieties, is nearly 25,000 MTs, of which only around 18,475 MTs (2006-07) is getting produced in the country and the rest being imported mainly from China. Indian domestic silk market has over the years been basically driven by multivoltine mulberry silk. Due to inferior quality of the silk produced, India could not meet the international quality standard. Though, R&D efforts have been made to improve the quality of multivoltine silk, even the best of multivoltine silk produced could not match the bivoltine silk in quality. Therefore, it is essential to enlarge the production base and improve current productivity levels of bivoltine silk to meet the international standards and quality demands of the power loom sector. Steps need to be taken to ensure that export oriented units having automatic state of the art weaving machinery.

Types of silks in India: India is a home to a vast variety of silk secreting fauna which also includes an amazing diversity of silk moths. This has enabled India to achieve the unique distinction of being a producer of all the five commercially traded varieties of natural silks namely, Mulberry, Tropical Tasar, Oak Tasar, Eri and Muga. Silk obtained from sources other than mulberry are generally termed as non-mulberry or Vanya silks. The bulk of the commercial silk produced in the world is mulberry silk that comes from the domesticated silkworm, Bombyx mori L. which feeds solely on the leaves of the mulberry (Morus sp.) plant. Tasar silk is copperish in colour, coarse in nature and is mainly used for furnishing and interiors and secreted by the Tropical Tasar silkworm, Antheraea mylittai which thrives on Asan and Arjun (Terminalia sp.). Rearing is done on naturally growing trees in the forests and is the main stay for many tribal communities in the states of Jharkhand, Chhattisgarh, Orissa, Maharashtra, West Bengal and Andhra Pradesh.

Oak Tasar is a finer variety of Tasar produced by the temperate Tasar silkworm, Antheraea proylei which feeds on natural oak plants (Quercus sp.) and is found in abundance in the sub-Himalayan belt. Eri silk is a silk spun from open-ended cocoons and secreted by the domesticated silkworm, Samia cynthia ricinii that feeds mainly on castor leaves. Muga silk is golden yellow in colour and an exclusive produce of India, primarily the state of Assam where it is the preferred attire during festivities. Muga silk is secreted by Antheraea assama that feeds on aromatic leaves of naturally growing Som (Persia bombycina) and Sualu (Litsea polyantha) plants.