Jute Fibre
Corchorus Capsularis and Corchorus Olitorious are two species of the genus corchorus (linden tree family), which are grown for jute fiber production. These are native to tropics and sub tropics, occuring as hubs or small shurbs.

Jute is chiefly grown in India and Bangladesh. The natural condition of these are ideal to its cultivation. The hot climate and rich alluvial soil of the Ganges and the Brahmaputra are very much suited to jute cultivation. The high humidity is also favourable. Of the two important varieties of jute Corchorus Capsularis is adapted to grow in the low land areas in clayey soil and can withstand floods, while Corchorus Olitorious is adapted to grow in high land areas in sandy loam soils and cannot withstand floods, but resist drought conditions to a certain extent.

The Jute Plant
Two species of jute plants are essentially alike but can be distinguished by their fruit. Fruits of Corchorus Capsularis are like capsules of about one third of an inch in diameter whereas fruits of Corchorus Olitorious being a pod of two inch long. Jute is an annual plant and grows upto 12 or more feet high with a straight cylindrical stem upto one inch thick in the base. The stems from outside consists of a bark, bast fiber bundles, pectins which join the woody portion to bast fibers, a woody portion and a central cavity.

Harvesting and Retting
The crop is sown in the spring and gathered in autumn.The stems are harvested by hand shortly after flowering but before the capsules can mature. The time for gathering is indicated by the fading of flowers : if left too long the fibers become coarse and woody, but if harvested too soon the fibers are weak.

The stems are cut into bundles and left to lie on the filed, ocassionally their leaves are stripped. Then the stocks are placed in retting basin (ponds, rivers, etc) and kept submerged 4-6 inches below the surface by suitable weights. The processing carried out for twelve to fifteen days depending upon the the region, water temperature and maturity of the stem. The fibers are less readily freed at the root than at the top. After retting the bark is easily separated from the stems by stripping with the hand. Old stalks are sometimes beaten with wooden hammer to break up the loose connections between fiber bundles and the surrounding tissues, after which former are readily peeled off. The strands are cleaned by rinsing water and rubbed with fingers. They are then dried, care been taken so that so that they are not exposed to strong sunlight.

The Jute Strand
Strands of jute are meshwork of fibers, are from 5-10 feet long and of pale yellow or yellowish brown colour. When first extracted they are soft, fine and lustrous, as well as being pliable, but on exposure they turn brown and become weak and brittle. A transverse section of jute consist 5-20 cells. While the strands of jute resemble those of flax, they differ in one respect, that the individual cells - the ultimates - which are cemented together, are so short that any treatment that removes the cement, completely disrupts the strand.

Ultimate Jute Fiber
The ultimate fibers of jute vary in length from 1.6 mm with mean length 2.5 mm so that they are very much shorter than flax (mean length 32 mm) or of cotton (mean length 25 mm). In diameter they are about 0.012-0.018 mm so that the ratio of length to breadth is only 150 which is very low for a textile fiber. A high length to breadth ratio is typical of nearly all fibers, that are spun and woven by traditional method, being of the order of 1000-2000 for wool, cotton and flax.

Physical properties
Jute fibers have a specific gravity of 1.48-1.50 and their specific heat is 0.324. Jute is a very good insulator of heat and electricity. The bound air within the material (Or fabric) offers a great resistance to heat transfer. The fiber is highly combustible too.

Jute is a highly hygroscopic fiber and its hygroscopocity in comparison to with that of pure cellulose is attributed to its large amourphous to crystalline ratio. the equilibrium moisture absorption of jute under extremely high humidity is 35-40 % of its dry weight.

The tenacity of jute varies from 3.5-4.5 gm per denier at 4 cm test length. At very short specimen lengths, the tenacity may be as high 6-7 gm per denier.It remains practically constant over the humidity range 35-80 %. Under very dry and very wet conditions, it decreases appreciably. Its breaking elongation under normal atmospheric condition is 1-1.2 %.

Stiffness of jute fiber is high at normal moisture content. On account of its stiffness and rigidity, jute fibers resist packing and twisting of fibers in the yarn and give rise to low inter fiber friction. Therefore a certain degree of pliancy is imparted to the fibers before drawing and spinning by applying an oil-in-water emulsion to the raw fibers.

Chemical Composition
Cellulose 64.4 %
Hemicellulose 12.0 %
Pectin 0.2 %
Lignin 11.5 %
Water-Solubles 1.1 %
Fat and Wax 0.5 %
Moisture 10.0 %