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Post Harvesting

Jute

Processing of Jute

The jute is second in world’s production of textile fibres. Jute is almost entirely a market oriented crop. As much as 90% of crop produced is necessarily to be sold and only 5% is retained by the farmers for domestic purposes. The growers usually market the fibre in the immediate post harvest period. The peak arrival months are September and October.

The crop is ready for harvesting when it is in small pod stage. If harvested before, the fibre is weak while if left until the seed is ripe, the fibre is stronger but is coarser and lacks the characteristic lusture. The plants are left in small heaps at different places in the field for two to four days when most of the leaves get dried up. After this period the plants are tied into bundles. At the time of bundling most of the leaves shed on the ground. The colour of the fibre is darkened if the leaves are allowed to remain during the process of retting. It is also thought that drying of the plants before retting facilitates the separation of the fibre. The bundles are then taken for steeping in water. In low lands where jute plants may be standing in water, steeping is carried out immediately after harvest.

Flow chart of jute processing

Bundle stalk

Retting

5 to 15 days

Stripping

Washing

Squeezing excess water out

Sun drying

2-3 days

Bailing

Kutcha packing

Storage

Shipping / Transport

Retting

It is a process by which fibres in the tank get loosened and separated from the woody stalk due to the removal of pectinals and other mucilaginous substances. This is usually affected by the combined action of water and micro-organisms. The tied bundles of jute stalks are taken to the tank or ditch for retting. The bundles are steeped in water at least 60 to 90cm in depth. Jute bundles rot better when steeped out at a depth of 15cm to 23cm below the surface in slow flowing clean water. The retting process is completed in 8 to 30 days.

When the barks separate out easily from the stick or wood retting is completed. When retting is complete, fibres are ready for extraction. Fibre must be extracted as quickly as possible otherwise the quality will suffer.

Stripping (Fibre Extraction)

This is a process of removing the fibres from the stalk after the completion of retting. Generally the fibres are removed from the stalk by any of the three methods. In the first method single plants are taken and their fibres are taken off. This method though very slow, results in good quality of fibres as it is free from pith, etc. The second method implies taking off a handful of stalks breaking at one end and stripping off the fibres by dashing it in a to and fro motion in water. The third method consists of washing the stalks first by standing in waist deep water and then stripping afterwards. None of the above methods is efficient as they are slow and the recovery is also low.

The fibre bundles lie beneath the bark, surrounded by gummy materials in the living plants. To obtain the fibre from the stem these entirely soft tissues must be softened, dissolved and washed away. This is done by steeping the stem in water, the bundle of stalks are laid in the ponds ditches or slow moving streams, weighted down the stones leaves, or clods of earth, and left for 5-15 days. A plentiful supply of water for retting is required. Approximately 2,800 gallons are needed to pond-set one tonne of green stalks yielding 112 leaf fibre. The optimum water temperature for retting is 26.70C. Retting is caused by micro-organisms which soften the tissues and gums, starting at the continue and extending outward so that the outer cells of the cortex are the last to disintegrate. Retting is better if the stems are uniform in thickness. The type of water which is used for retting has an influence on the value of the fibre. The best place for retting is slow running streams which are free from pollution as possible.

The fibre is taken from the water as soon as possible when the daily examination of the stems shows that the bark can be removed easily from the rest of the stem. This stage is called stripping. A bunch of stem is held in one hand and the root end tapped lightly with a mallet. This action frees the fibres at the root of the stalk. The labourers then grasps the fibres and by jerking and lashing the stems about in water, loosens the rest of the fibres, picks off odd pieces of bark, washes, the fibre and squeezes the excess water out. The fibre is then collected and laid out on bamboo racks to dry for 2-3 days.

Washing and drying

Before hanging for drying the extracted fibres are washed in clean water. The dark colour if present can be removed to a great extent by dipping the fibre in tamarind water for 15 to 20 minutes and then washing in clean water. Five kilograms of ripe tamarind fruits in two buckets of water will give the necessary solution to treat about 5.5 to 7.5 quintals of fibre. The fibres are hung on bamboo railings for drying which takes 2-3 days. After drying the fibres are ready to be sold in the market. The fibre extraction is done during the months of August and September.

The yield of the crop depends upon the quality of the soil and the attention which the fibre has received in its various stages. The fibre content of plant generally ranges between 4.5 to 7.5% of the green weight with an average of 5.5%. The normal average yield per hectare in India is estimated at about 11 to 21 quintals.

Grading

There are two stages of grading, one for the home trade and another for the export trade. Grading factors for jute are colour, length, firmness of fibre, lustre, strength, clearness, freedom from defects, and the amounts of root end which will have to be cut off. The preliminary grading is done by kutcha balers.

Kutcha Balers grading of raw jute.

Grade

Characteristics

Tops

Very strong fibre, excellent colour and lustre free from all defects

Middles

Strong, sound fibre, average colour for the district, free from specks, runners and hard crop end

Bottoms

Sound fibre,medium strength, free from hard-centred fibre

B- Bottoms

Sound fibre, medium strength, not suitable for higher grades

C- Bottoms

Medium strength fibre, any colour, free from runners and cropiness

X-Bottoms

(cross bottoms)

Weak harse Jute, free from tangle Jute and stick jute of any sort, free from dust and cutting

Spinning process:

Type of jute yarns manufactured can be classified according to the use to which they will be put:

  1. Fine Yarns: These yarns are of low count for making fine fabrics for tailers inter-lining and the like. The volume of trade in these is comparatively small since they are expensive and the top grades of the jute must be used to enable such yarns to tie spun.

  2. Hessain Qualities: Medium weight yarns for weaving cloths for general packing purposes, linoleum backings carpet backings etc.come under these qualities.

  3. Carpet yarns: These are yarns usually medium-heavy weight yarns of good quality either single or top-play for the carpet industry.

  4. Sacking yarns: These are medium/heavy yarns of lower grade used for the manufacture of sacks and bags.

Type A, B and C can be divided into warp and weft qualities; the warp being superior to the weft as it must withstand the tensions of weaving and undergoes little strain.

Marketing of Jute

The important link in the chain of the movement of jute from the growers to the home mills or the exporter is collection, assembly storage and transportation at several stages. The first link is the bi-weekly village market or hat. As the top becomes ready in June or early July, dealers travel round the homes of the growers buying their jute and then taking it to the hats where they and some of the growers who bring their own jute to the market sell or merchants. The jute at the hat is sold in an unassorted fashion, the only distinction being between white-Tossa jutes. The fibre is transported by country boat, back animal, or cart to the larger secondary centres where jute buying and selling goes on daily during the seasons.

The fibre is graded into Tops, middles, B, C and X-Bottoms by the Kutcha baler. A kutcha baler is one who grades the raw jute and packs it into kutcha bales weighing about 250 pound for use in the home trade. A pucca baler grades the fibre for export, cuts off the hard root end and presses the jute into pucca bales weighing 400 pounds of 49" x 18" x 20". This is done to some valuable cargo space for the material which is to be supplied overseas. The home mills buy their jute either from the primary or secondary centres being the chief sources.