NATURAL ANIMAL FIBRES
SILK
Silk is the only example of a
natural filament yarn.
The continuous filament can be up to three miles long and,
size for size, it is stronger than steel.
It is both elastic and absorbent.
Silk was being cultivated in China as long ago as 2600 BC,
and is renowned
for its lustre and brilliance.
There are two categories of silk
cultivated and wild
cultvated silk
- Bombyx is a cultivated silk produced on a silk farm
by the Bombyx mori silkworm
- The diet of this silkworm is mulberry leaves
- The leaves of the black-mulberry tree are gathered daily to be fed
to the silkworms
- The caterpillar spins a cocoon when it has grown
to about 7cm (3inches) long
- The caterpillar extrudes two filaments which it cements
together with a gum called sericin
- In order to preserve the unbroken filament, cultivated
silkworms are not allowed to hatch
- When eight days old the cocoons of silk filament
are steamed to stifle the grub which is inside
- The cocoons are then softened in hot water to release the gum,
and the silk filament is wound off
- Filaments from a number of cocoons are usually wound off together,
to be spun into a mult-filament yarn
- The cultivated silkworm produces the best white filament
wild silk
- Tussah silk is produced by wild silkworms which feed on oak leaves
- The caterpillar spins a cocoon when it has grown
to about 7cm (3inches) long
- When the wild silk moths hatch and eat their way out of the cocoon,
they damage the silk filament
- After the filament has been spun this damage shows as small slubs in the
yarn. It is these slubs that give some woven silk fabrics (such as dupion),
that charactoristic natural texture
- It is usual to cut the long filaments of wild silk into staple lengths, which are then
carded before spinning
- Wild silk is coarser and stronger than cultivated,
and is creamy or brown in colour
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to read about vegetable stalk fibres
