Hemp Fibre
The hemp plant, Canabis Sativa is a member of the mulbery family has been used for cordage, and to some extent for clothing. It is grown mostly in Russia, also in Poland, Italy, France, India and China. During the 1939-1945 war it was also sown in USA. However the best qualities of hemp come from Italy, they are generally creamy white, long, soft, lustrous and pliable.

Hemp plant does not thrive in arid conditions and water logged areas. Soils in the temperate zones are suitable for hemp cultivation, but must be freshly tilled to considerable depth. The plants have astonishing adaptability to altitudes. Thus,it can be grown at a height of nearly 8,000 feet. However, it takes more time to grow and need higher summer temperatures then flax. The field for cultivation of hemp should contain soft, rich and moist soil.

The Hemp Plant
Hemp is an annual plant and grows to a height of 12 feet or more. Hemp is a dioecious plant, i.e. the male and female flowers are born on separate plant. To obtain tall, straight, unbranched stem close sowing is necessary. The stems are about half inch thick. In cross section the various layers of the stem of hemp plant are similar to those of the flax stem. Epidermis on the outside, cortex, bast fibers, wood and finally a hollow space which may occupy one half of diameter of the stem.

Harvesting and Retting
The sowing of hemp is done in mid April. It is essential to choose the right moment for harvesting. If the crop is cut early, the fibers will be fewer, weaker and less glossy. If the harvesting is delayed the fibers turn out woody, harsh and lacking in lustre. Generally harvesting is carried out when the lower leaves fall off and the stems begin to yellow. The harvest usually takes place in August or September. As the male plant is exclusively grown for fibers and the female plant for both fiber and seeds and as the ripening of the fibers and seeds do not coincide, a laborious plucking out of each plant is necessary. In order to get quality fiber, the male plants are plucked 2-3 weeks before the female plants.

In the retting of hemp certain bacteria bring about the separation of fibers from the softer parts of the stalk. The male plant can be retted in 10 days, while the stronger female plant needs about 3 weeks for retting. There are two process for retting. In dew retting the stalks are left to lie in the field to allow humidity and heat to stimulate the growth of micro-organisms,which contribute to the isolation of the fibers. Fibers produced by dew retting are of medium length and dark in colour.

In water retting, as practised in Italy, hemp is treated in ditches, some of them being lined with masonry. River or well water is used for retting. The microbes are found in ditches and on the bark of the stems. The water should not be turbid with impurities or soil but clear and free from aquatic plant. Water low in lime and free from chloride is excellent for retting. The upper most hemp bundles should be submerged at least four inches below the water surface and the undermost bundles should be at least twenty inches below the surface.

On the first day of retting the air entrapped between the stems and contained within the stems bubbles to the surface of water. On the second day the water turns acidic. Starting from the fourth day, a steadily volume of gas developes until the process is stabilised. The chlorophyll disappears, disintegrating into small irregular platelets and the fiber strands begin to separate from the woody portion. The retting process is continued and is found to be complete when the fibers show a white colour. The entire retting period depends on climate, water and air temperature, type of water available and the number of previous retting operations carried out in the same water. Retting results in a bulk loss of 10 to 30%. The fibers are then removed from the retting tank after washing in the same water. The bundles are then dried and stored.

Ultimate Hemp Fiber
The ultimate hemp fibers consist of cells which average about 20 mm in length, varying from 5 mm to 55 mm, they have a mean breadth of 0.022 mm varying from 0.01mm to 0.05 mm. the ratio of length to diameter is about 1000. The cells are partly lignified, and the lumen is angular and broader than flax. The ends of the hemp fibers are thick walled and blunt.

Physical properties
Moisture Regain - 12%
Specific Gravity - 1.48 - 1.50
Specific Heat - 0.323

Chemical Composition
Cellulose 67.0 %
Hemicellulose 16.1 %
Pectin 0.8 %
Lignin 3.3 %
Water-Solubles 2.1 %
Fat and Wax 0.7 %
Moisture 10.0 %