Hemp

                                   Hemp

Hemp is the name of soft durable fiber that is cultivated from the plant of Cannabis genus.

                                  

The variety of appearances for cannabis. Only C. sativa (left) is suited for industrial hemp, but it also has medicinal varieties.

Like flax, hemp is a bast fiber. It grows to a height of 3m (10ft) or more.

The hemp plant is now cultivated in almost every European country, and in many part of Asia.

                 Production and Processing

The hemp plant is harvested and processed in a manner similar to that used for flax.

Fiber is freed from woody matter dy dew-retting and water-retting, followed by breaking and scutching. 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 being harvested

Dyeing:-

Hemp is used very largely in its natural state. In dyeing direct colors are often used. Basic dyestuffs provide bright shades, the fiber being mordanted (A substance that combines with dye and is used to fix it in a material) with antimony and tannin.

Structure and Properties:-

Hemp is a coarser fiber than flax. It is dark in color and difficult to bleach. The fiber is strong 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.

Strands of hemp fiber may be 2m (6ft) in length. The individual cells are, on average, 13-26mm (1/2-1 in) long. They are cylindrical in shape, with joints, cracks, swellings and other irregularities on the surface.

Like flax, the cells of hemp fiber are thick-walled. They are polygonal in cross-section. The central canal or lumen in broader (large than usual side to side) than flax and ends of cells are blunt ( lacking sharp edge or point).

The hemp fiber is more lignified than flax, and is consequently stiffer.

                                      Hemp stem showing fibers

                

                                      PROPERTIES

Physical Properties:-

Tenacity                                       5.6g/d

Extension                                    1.7%

Chemical Properties:-

Cellulose                                     67%

Pectin                                          0.2%

Water Soluble                          2.1

Fat, Waxes                                 0.7%

Others                                         19.4%

Hemi cellulose + Lignin

Hemp in Use:-

              Hemp is used for almost every form of textile material.

1-   It has been made into fine fabrics by skilful spinning and weaving.

2-    Hemp is used mainly for coarse fabrics such as sacking and canvas, and for making ropes and twines.

               

                  Hemp rope                                                     A sack made from hemp fiber

3-    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 (up to 50% hemp).