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Sericulture
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Sorting cocoons
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Softening and sericin
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Reeling
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Throwing
1 ) Sericulture:
The cultivation of silkworms for the purpose of producing
silk is called sericulture. The best raw silk is obtained from the species of
moth called Bombyx Mori. Breeding of silkworm occurs once in a year but under
scientific conditions, they may be hatched three times a year. 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 charge their skin for four times and are formed into
caterpillar of about 9cm long. Now they are ready to spin cocoon for which
racks, clusters of twigs or straw are provided.
The caterpillar have small openings under their jaws called
spinnerets through which they secret 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.
2 ) Sorting cocoon:
The cocoon is sorted according to color, shape and texture,
as all these affect the final quality of the silk. Cocoons may range from white
or yellow to grayish, depending on the source abd the type of food consumed
during the worm stage.
Cocoon from China are white, Japanese cocoons are creamy
white and yellow, Italian cocoons are yellow.
3 ) Softening the sericin:
After the cocoons have been sorted, they are put through a
series of hot and cold immersions, as the sericin must be softened to permit
the unwinding of the filament as one continuous thread.
4 ) Reeling:
Reeling may be
achieved manually or automatically. The cocoon is brushed to locate the end of
the fiber. The method is as simple as it is laborious. It is threaded through a
porcelain eyelet, and the fiber is reeled onto a wheel. Meanwhile, diligent
operators check for flaws in the filaments as they are being reeled.
As each filament is nearly finished being reeled, a new
fiber is twisted onto it, thereby forming one long, continuous thread. Sericin contributes
to the adhesion of the fibers to each others. The average cocoon reels off
about three hundred yards in a single thread.
5 ) Throwing:
The production of yarn from reeled silk known as throwing
consists of adding twist or of doubling and further twisting these strands in
to desired size.
Different types of silk:
I.
Mulberry silk:
Produce by silk worm(Bombyx Mori) fed on
Mulberry leaves.
II.
Tussar silk:
Larvae of several species of moth such as
Antheraea mylitta, Antheraca proylei, Antherea pernyi and Antheraca yamamai
produce this silk. The insects mostly live in the wild on bushes and trees on
which they feed.
III.
Katiya silk:
The portion of Tussar cocoons leftover
after about 60% reelable silk is spun into katiya yarn.
IV.
Balkal silk:
The peduncle(silk that anchors the cocoon,
it is very week) are utilized for production of Balkal yarn.
V.
Muga silk:
It belong to same family as Tussar. It is
popular for its natural golden color, glossy fine textures and durability. Muga
silk is produced by Antheraea assama westwood which is an endemic species
prevent in the Brahmaputra valley and adjoining hills.
Muga silkworm is a polyhageous insect which
feeds on leaves of Som, Soalu and other plants which grow abundantly in
Brahmaputra valley.
VI.
Eri silk:
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 names as Eri. This is the only completely domesticated
non-mulberry variety. Its silk is as it cannot be reeled.
VII.
Spun silk:
A silk yarn made of short lengths of silk
obtained from silk wastes, pierced cocoon 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.
VIII.
Noil silk/waste silk:
A noil short fiber removed in combing
operation of yarn making of spun silk is spun into Noil yarn. Noil is mostly
produced in Karnataka and Madras.
IX.
Dupion silk:
An irregular, riugh silk reeled 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.
X.
Filature silk:
A raw silk which is reeled by machine as
distinct from silk prepared by hand in cottage industry.
XI.
Matka silk:
Mutka silk is obtained from waste Mulberry
silk by hand spinning without removing the gum. Cocoons required to produce
Matka are mainly obtained from Karnataka and Kashmir but spinning is mostly
done in the villages of malda and Murshidabad districts in west Bengal by hand
spinning.
XII.
Spider silk:
The silken filament spun by spders is so fine
that they can often be seen only with difficult. The golden garden spider spins
a filament only 0.0001 in diameter. Many attempts have been made to use spider
silk as a textile fiber.