Lynne Wong's PhD thesis

Figure 3.4. The four cane varieties chosen for fibre extraction.
3.3 EXTRACTION OF PLANT FIBRES
Some fibres are embedded within the tissues of the plant, which have to be removed to
obtain the fibres, while fibres of cotton and kapok need only be removed from the seed
case. Fibres can be extracted from tissue either by beating and/or scraping the fresh leaves
or by softening the tissues by retting. For some fibres, retting alone is not sufficient and a
further chemical treatment needs to be carried out, for example, the use of alkaline
solutions in degumming of ramie (Jarman, 1998), which is an Asiatic shrub, Baehmeria
nivea, in the nettle family, yielding a fibre used in making textiles, upholstery, thread and
paper.
3.3.1 Industrial extraction of fibres from flax, hemp, jute and sisal
Jarman (1998) described the dew retting and water retting methods of fibre extraction from
flax and hemp stem. In the former, freshly pulled straw is spread in the field in relatively
thin layers; rain, snow or dew causes fungi and bacteria to enter the stomata of the stems
and attack the pectin binding the fibres together. In the water retting method, retting can
be carried out either in cold water in rivers, pools or ditches: the small, loosely bound
bundles are submerged in water and weighted down with large stones to keep them
submerged; or in a tank using warm water at about 28 °C. In cold water retting, at
temperatures below 15 °C, there is little bacterial activity whereas in warm water retting,
the principal retting organisms are anaerobic bacteria. Once the retting is completed after
days, the straw bundles are rinsed and taken back to the field where they are piled in open
“wigwam” fashion and allowed to dry completely before fibre extraction. The process
consists of beating and shaking the broken straw to remove most of the wood and finally
“hackling” to align the fibres and remove the woody stem portions (Jarman, 1998).
In jute stems, Jarman (1998) also described the retting method whereby the bundles of jute
stems are immersed in pools, canals, slow-moving streams or ponds at a depth of 1-2 m.
The bacteria on the stem will attack the plant tissues surrounding the fibres, softening them
sufficiently so that they can be washed away leaving the fibres unaffected. When retting is
complete, the bundles must be removed from the water and the fibres stripped from the
stem before it over-rets. The retted stems are first gently beaten at the base with a mallet to
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