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Water
retting
The preferred method of retting is water retting, as it
yields superior quality fiber. In this method, bundles of the
plant stalks are submerged in water. The time duration for the
plants to remain submerged in water should be carefully monitored.
If the submerging time allowed is not enough, the separation
process becomes very difficult and so the yield is affected. On
the other hand, if the submerging time allowed is too much, the
quality is affected and the extracted fiber is weak.
Trial and error
methods have resulted in a process known as double retting. In
this process, plant stalks are retted in water for a lesser time
than optimum, taken out and dried for a long time and then they
are retted again. The fiber extracted after this process is
generally of a very superior quality.
Stagnant
water retting
Another method
employed is natural water retting. Stagnant or slow moving water
like ponds and bogs are used for this. The stalk bundles are
dropped into the water and are weighted down with stones or logs.
The submerging time is decided depending upon the temperature
of the water and the mineral content of the water. The submerging
time allowed varies between 10 days to two weeks.
Tank
water retting
Tank retting is yet another method using for retting
fiber yielding plant stalks. Control can be exercised over water
conditions and thus the quality of fiber obtained is better and
more consistent. Tanks
constructed for the purpose are used for submerging plant stalks.
Water is changed after the initial eight hours of submerging. This
aids the retting process, as a lot of waste and toxins are removed
along with this water. The waste water that is removed is treated
and then used as liquid fertilizer as it is rich in chemicals.
The
next stage
Straw is the name used to refer to the stalks that have
completed the retting process. This straw is then put through the
process of drying in open air and then stored for a while to allow
curing to occur. Curing aids the process of fiber removal.
The next stage is
the breaking process in which the woody portion of the straw is
broken. This process may be done either by hand or through
machines. Machines with rollers are used for this process when
done on a large scale.
A process known
as scuthing, wherein broken pieces are removed by either beating
or scraping the straw, follows breaking. Some machines perform
both the beating and the scuthing process. The waste material from
the scuthing process is used for paper manufacture. Another
by-product of the scuthing process, woody pieces referred to as
shives are used as fuel for heating the water used for retting.
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