In many parts of Asia, the fiber hemp has been in use since prehistoric times. Ancient records describe the use of hemp fiber in China 2800 B.C. during the early Christian era, production of hemp spread to the countries of Mediterranean Europe, and since then the fiber has come into widespread use throughout the world.
Like flax, hemp is a bast fibre. It becomes from the plant cannabis sativa, an annual of the family Moraceae, which grows to a height of 3m (10 ft) or more. The hemp plant is now cultivated in almost every European country and in any parts of Asia. Important producing countries include the Soviet Union, Yogoslavia, Roumania ad Hungary.
Production and Processing of Hemp Fiber:
The hemp plant is harvested and processed in a manner similar to that used for flax. Fiber is freed from woody matter by dew retting or water retting, followed by breaking and scotching. The fiber is softened by pounding it mechanically or by hand.
Hemp can be separated from the straw by a mechanical process more easily than in the case of flax. Green hemp is now produced commercially in this way.
Hemp is used very largely in its natural state. When dyeing is necessary direct colors are often used. Basic dyestuffs provide bright shades, the fiber being mordanted with antimony and tannin.
Structure and Properties of Hemp Fiber:
Hemp is coarser fiber than flax fiber. It is dark in color and difficult to bleach. The fiber is strong and durable and is used very largely for making string, cord and rope.
Some Italian hemp is produced with great care. They are light in color and have an attractive luster similar to that of flax fiber.
Strands of hemp may be 2m in length. The individual cells are on average 13-26mm long. They are cylindrical in shape with joints, cracks, swellings and other irregularities on the surface.
Like flax fiber, the cells of hemp fiber are thick walled. They are polygonal in cross section. The central canal or lumen is broader than that of flax, however and the ends of the cells are blunt. The hemp is more lignified than flax fiber and is consequently stiffer.
Uses of Hemp Fiber:
During its long history, hemp has been used for almost every form of textile material. It has been made into fine fabrics by skillful spinning and weaving or carefully produced fibre, notably in Italy where a hemp fabric is similar to linen is made. Now a day, hemp is used mainly for coarse fabrics such as sacking and canvas and for making ropes and twines.
Hemp can be cottonized by a process similar to that used for flax, so that the individual fibers are freed. Cottonized hemp does not spin easily alone but it gives useful yarns when mixed with cotton.