The method of separating the bast layer (in which the fibres are
embedded) from the stem of the plant requires a large supply of water,
since the plants must be completely submerged in the water for a
period varying from 8 to 30 days; such time is dependent upon the
period of the year and upon the district in which the operation is
performed.
The above operation of detaching the bast layer from the stem is
technically known as "retting," and a good type of retting or
steeping place is an off-set of a run, branch, or stream where the
water moves slowly, or even remains at rest, during the time the
plants are under treatment.
The disintegration of the structural part of the plant is due to a
bacterial action, and gas is given off during the operation. The
farmer, or ryot, and his men know what progress the action is making
by the presence of the air bells which rise to the surface; when the
formation of air bells ceases, the men examine the plants daily to
see that the operation does not go too far, otherwise the fibrous
layer would be injured, and the resulting fibre weak. The stems are
tested in these examinations to see if the fibrous layer, or bast
layer, will strip off clean from the wood or stem. When the ryot
considers that the layers are separated from the core sufficiently
easy, the work of steeping ceases, and the process of stripping is
commenced immediately. This latter process is conducted in various
ways depending upon the practice in vogue in the district.
In one area the men work amongst the water breaking up the woody
structure of the retted plants by means of mallets and cross rails
fixed to uprights in the water; others break the stems by hand;
while in other cases the stems are handed out of the water to women
who strip off the fibrous layer and preserve intact the central core
or straw to be used ultimately for thatching. The strips of fibre
are all cleaned and rubbed in the water to remove all the vegetable
impurities, and finally the fibre is dried, usually by hanging it
over poles and protecting it from the direct rays of the sun.
If the water supply is deficient in the vicinity where the plants
are grown, it may be advantageous to convey the fibrous layers to
some other place provided with a better supply of water for the
final washing and drying; imperfect retting and cleaning are apt to
create defects in the fibre, and to cause considerable trouble or
difficulties in subsequent branches of the industry.
Fig. 3 illustrates photomicrographs of cross sections of a jute plant.
The lower illustration represents approximately one quarter of a
complete cross section. The central part of the stem or pith is
lettered A; the next wide ring B is the woody matter; the outer
covering or cuticle is marked C; while the actual fibrous layer
appears between the parts B and C, and some of the fibres are
indicated by D. The arrows show the corresponding parts in the three
distinct views. The middle illustration shows an enlarged view of a
small part of the lowest view, while the upper illustration is a
further enlarged view of a small section of the middle view. It will
be seen that each group of fibres is surrounded by vegetable matter.
[Illustration: FIG. 3 PHOTOMICROGRAPHS OF CROSS SECTIONS OF A JUTE
PLANT]
Another method of stripping the fibrous layer off the stems or stalks,
and one which is practised in certain districts with the object of
preserving the straws, consists in breaking off a small portion, say
one foot, at the top end of the stem; the operative then grasps the
tops by the hand and shakes the plants to and fro in the water, thus
loosening the parts, after which the straws float out, leaving the
fibrous layer free. The straws are collected for future use, while the
fibre is cleaned and washed in the usual way.