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Origin
According to Chinese legend, the culture and use of Silk
originates 4000 years back on the banks of Hwang-ho or Yellow
River. The empress Si-Ling-Chi learned how to rear the
caterpillars on mulberry leaves and how to unwind the silk from
cocoons. The secret of silk-making was kept close by the Chinese
and was smuggled into Japan early in the Christian era and also
reached India.
Raw Silk is now extensively produced in China, India, Vietnam,
Russia and Japan.
Sericulture
Silk is a strong, soft, lustrous fibre extruded by certain kinds
of moth and spiders. The cultivated silk variety is produced by
the species Bombyx mori. There are other less-cultivated species,
known as Wild Silk (such as Tussar feeding on Oak leaves, Eri on
Castor-oil plant leaves and Muga on variety of polyanthus leaves
like Som, soalu etc.).
Silkworm eggs (popularly known as seeds) are laid out on the
mulberry leaves to hatch out into caterpillars about 2 mm long.
They grow rapidly, eat voraciously and end up about 30 mm long
after 4-5 weeks. During this time, they change skins 4 times.
After final skin change, straw frames are provided in which
silkworms makes its cocoon. Cocoon-making takes further 8 days,
It takes the silkworm another 3-4 days to transform into pupa and
another 15 days for the moth to emerge. Like all other moths, the
insect passes through four stages in it's life : Egg,
Caterpillar, Pupa (or chrysalis) and perfect insect. Female moth
lays 200-500 eggs at a time, normally in the summer.
Twin silk threads (fibroin- in fluid form) are extruded through
two glands together with a gummy substance -sericin, which binds
the filaments together as well as forms the walls of cocoon. By
moving its head from side to side, the silkworm lays the filament
in a series of figure `8' gradually building from wall to wall.
The sericin sets hard and cocoon develops into a shape like
peanut with the chrysalis inside
Silk
Varieties
India basically produces four different varieties of Silk:
Mulberry |
Tussar |
Muga |
Eri
Certain other types Silks which are Bye-products of main process
are also produced in India, namely,
Dupion Filature :: Matka Katiya :: Ghicha Balkal
:: Noil Spun
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The main
production centres being the states of Karnataka, West Bengal,
Madhya Pradesh, Orissa, Bihar, Maharastra, Assam and to some
extent Kashmir.
Mulberry:
The Cultivated silkworm, Bombyx mori
feeds on the leaves of the mulberry tree. This variety of Silk is
mostly cultivated in Karnataka and Kashmir.
Dupion An irregular, rough silk reeled from double
cocoons or cocoons spun side-by-side which are interlocked,
making it necessary to reel them together. The unevenness of the
yarn confines its use.
Filature A raw silk which is reeled by machine as
distinct from silk prepared by hand in cottage industry.
Matka silk is obtained from waste Mulberry silk by
hand spinning without removing the gum (sericin). Cocoons
required to produce Matka are mainly obtained from Karnataka and
Kashmir but spiining is mostly done in the villages of Malda and
Murshidabad districts in West Bengal by women by hand spinning.
Some of the well-known villages such as Sujapur, Islampur,
Dariapur have given their names to the Matka yarns produced in
these villages.
Tussar:
Tussar Silk is produced by the larvae of
several species of moth such as Antheraea mylitta, Antheraca
proylei, Antherea pernyi and Antheraca yamamai.The insects mostly
live in the wild on bushes and trees on which they feed. Tussar
silk is spun by the worm in a single-shelled, oval cocoon, with a
fine-grained, hard, non-flossy shell. The cocoons are generally
yellow or grey and are hard & compact.
The cocoons are boiled in chemical solution or treated with
enzyme to soften. Thereafter yarn is reeled either in dry process
(by drying the cocoons) or by wet reeling process.
The portion of Tussar cocoons leftover after about 60% reelable
silk is spun into Katiya yarn.
The pierced cocoons are spun into Ghicha yarn while peduncles are
utilised for production of Balkal yarn.
Muga:
Native of Assam and named after Assamese word
"Muga" which indicates the amber (brown) colour of cocoon. It
belongs to same family as Tussar. It is popular for its natural
golden colour, glossy fine textures and durability. Muga silk is
produced by Antheraea assama westwood which is an endemic species
prevalent in the Brahmaputra valley and adjoining hills.
Muga silkworm is a polyhageous insect which feeds on leaves of
Som, Soalu and other plants which grows abundantly in
Brahmapautra valley.
Eri :
The word Eri is a derivative from Sanskrit
nomenclature for Castor Plant, eranada. Castor leaf is the main
food for the Eri silkworms and so named as Eri. This is the only
completely domesticated non-mulberry variety. Its silk is spun as
it can not be reeled.
Spun Silk A Silk yarn made of short lengths of silk obtained from
silk wastes, pierced cocoons or floss which gives yarn its
characteristic brilliance. There are two grades of yarn Schappe
and Bourette. It is spun on special machinery which in some ways
is akin to cotton and worsted.
Noil Short fibres removed in combing operation of yarn making of
Spun silk is spun into Noil yarn. Noil is mostly produced in
Karnataka and Madras.
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