Coir fibers are extracted from the fruit coconut. It grows in the part between the husk of the coconut and its outer shell. The color of this fiber is golden, therefore it is also known as Golden Fiber. However they are not initially golden in color, but of pale color. At later stage when fibers become hard, they acquire yellowish-golden color because of the lignin deposits on its walls. Its structure is narrow and hollow.
Coir fibers are water-proof in nature, also to the sea water, which is a distinguishable property. There are mainly two types of coir - white coir and brown coir. For processing of white coir both sea and fresh water is used, whereas for brown coir fresh water is used.
Properties of coir
- It is a bad conductor of heat. It provides padding against extreme temperatures and sound.
- It is easy to wash and clean, which makes them highly durable and maintenance free.
- It is unaffected by fungi, rot and other moths. As it is resistant to moisture the growth of micro-organisms is barred.
- Even if it is used for many years it does not loose its shape easily.
Types of coir
The types of coir - brown coir and white coir are categorized on the basis of the stage of the fruit when they are extracted from it, i.e. whether the coir is extracted from an immature coconut or fully ripped one. White coir is extracted from the husks of coconut which is not fully ripen and it is comparatively less stronger and more softer. Brown coir is extracted from the husks of coconut which is 100% ripened.
- White coir
As it is derived from immature husks, these husks are submerged in water for about ten months time. In this time period the plant tissues covering the coir fibers break down due to chemical reactions of the micro-organisms. Then the husks are hand beaten which separates the long fibers. The fibers further are dried in the sun, cleaned and sent for spinning where they are converted into yarn. These yarns are useful for making ropes, mats, etc.
- Brown coir
The husks are immersed into the slow flowing water, were the fibers get swollen as a result become soft. The long fibers and shorter fibers are separated from each other. The shorter fibers are also known as mattress fibers and longer ones are known as bristle fibers. They are first cleaned, sun dried and packed. Coir fibers are wavy in structure and have elasticity. The ropes are made by twisting these fibers. The long fibers are cleaned by water, dried in the sun and made into bundles. They are then made straight by steel combs and dyed with the desired colors.
The procedure for obtaining coir
Harvesting of the fiber
The coconuts are obtained from the trees, fetched by the climber with the help of the bamboo pole and a knife. As it is described earlier the two types of coir are extracted from different stages of the coconut, the unripe coconut are allowed to dry in the sun for about a month. Whereas the fully ripened coconuts are husked as soon as they are fetched from the tree, then the fruit is separated from the seed. Earlier this work was done only manually but now-a-days husking machines do this work at many places.
Retting of the fiber
Retting is a procedure where the husks are decomposed in either salt water or fresh water, encouraging the growth of micro-organisms. At this stage the coir fibers separate from the husk leaving behind residue which is known as coir pith. Retting in salt water is used for unripe coconut husks and fresh water for ripe coconut husks.
Salt water retting requires the unripe green husks to be soaked in saline water. Generally they are soaked in pits near the ocean. This method takes about 8-10 months time duration. If microbes are added artificially to the water, then this procedure will not take much time.
In freshwater retting the fully ripened husks are soaked in pits filled with water along the river banks. Or else put in the net which is submerged in river water by adding some weight to the net that keeps them dipped in the water. This procedure takes about time period of 6 months. Due to advancement in technology, mechanical machines are being used for retting. The unripe coconut husks are dry milled, thereafter crushed in crushing machines. Further they are required to be soaked in water for about 1-2 days only and at last dry milling is done again. In case of ripe husks, they are crushed in crushing machines then undergo the retting procedure for maximum of 10 days.
Defibering is done both manually and mechanically. In manual process the retted husks are hand beaten with wooden hammer that separates the fiber from the residue. Then are further sorted out by hand. In mechanical procedure, the retted husks are put into steel drums with beaters, these machines operate with the help of motor. The rotating drums with steel spikes further separate the fibers.
The residue is washed and combed manually or mechanically to obtain mattress fiber. This fiber is then allowed to dry in the sun.
Finishing of the fiber
Both bristle and mattress fibers are compressed by hydraulic press. In case of mattress fibers, they are combed and packed into a bundle of loosely coiled yarns whereas bristle fibers do not require to be combed. Now these bundles of yarn can be spunned into desired products by the manufacturer.
Coir is the natural fiber which has no effect of salt water on them. Thus are used for making fish nets and marine ropes. White coir is used is mainly used for making ropes, mats, alternate for milled peat moss. Brown coir is used to for sacks, mattresses, brushes and doormats. Its pads are also useful as erosion control tool and cushioning of the upholstery used by certain automobiles companies.
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