Hemp is a plant with infinite resources from which we can obtain food, cosmetics, fuels, fabrics, paper, etc. Its use has ancient origins: for thousands of years, the sailcloths of boats, including those of the Phoenicians, have been made with hemp, since it is the only natural fabric that resists the saltiness of the sea; in China, where paper production began, a small piece of it was found that dates back to the first century BC.
Until 1975, when the law came into force that banned the cultivation of all hemp, world paper production derived from this plant was 90%; then there was a long period of decline that lasted until 1998, when a new law allowed the cultivation of Cannabis sativa with a low THC (tetrahydrocannabinol) content, the narcotic active ingredient, which by law must be less than 0.2%. Currently only 5% of the paper produced in the world comes from annual plants such as hemp, flax, cotton, etc.
The use of the hemp plant
Paper is obtained from the stem, both from its external part, made up of fibres, and from the internal, woody part called hurd.
The hemp stem is made up of:
- Approximately 15-20% from fibres
- Approximately 80% from hemp
- 4% from lignin and pectin, which constitute the organic glue.
Long fibres are used to make fabrics, while medium fibres, called tow, are used to make paper (and nowadays only in rare cases are they also used in the hydraulic field).
The medium fibres, obtained from the fibrous part of the stem, are 2 mm long and have a thickness of 0.02 mm. From them a fine, thin, hard and slightly rough paper is obtained. While with the hurd, the woody part of the hemp, a type of soft paper is produced, rather thick and a little less resistant.
The qualities of hemp paper
This type of paper, compared to others, is much stronger and more resistant, almost indestructible, because it does not use acids to produce it, which make other types of paper subject to decomposition over time. The lack of treatments also prevents yellowing. It is therefore a strong and extensible paper, resistant to tears and lacerations, to attacks by mold and insects, resistant to heat and light.
An “eco-friendly” plant
Hemp is an annual herbaceous plant with an erect cylindrical stem, 80 cm to 5 m tall, which produces an enormous quantity of biomass with which energy can be created.
Growing hemp has great environmental advantages, including avoiding cutting down trees to make paper, considering that trees take about 20 years to develop while hemp only grows in 3-4 months, and that with one hectare of land cultivated with hemp, as much paper is produced as a 4-hectare forest would produce.
Hemp is a very rustic and resistant plant that does not require emergency watering or fertilizers to grow. It develops so quickly that in the field where it is cultivated, spontaneous weeds cannot grow, suffocated by its thick vegetation, it is therefore a plant that does not even require weeding. Furthermore, it improves the fertility of the soil, as the leaves that fall enrich it with mineral substances and the long, robust roots improve the structure of the soil.
The production of paper from hemp fibers does not require acids, only small quantities are needed for the processing of the shives; on the contrary, many chemicals, such as sulphates and sulphites, are needed to dissolve and separate the lignin fibres in the trees, contained in quantities of 20%.
Finally, the hemp plant is so strong and resistant that the paper can be recycled up to 7 times, unlike other types of paper that can be recycled a maximum of 3 times.
From plant to paper
Here are the various operations necessary for the transformation process:
- cleaning of soil, stones and foreign materials
- separation of all the fibres with mechanical or chemical processes to give rise to hemp pulp
- cutting of fibers to size, according to a given size, to make sheets of paper
- division of the fibres to be classified in order, discarding those that are too thin, or too short or too long
- for bleaching, a little hydrogen peroxide is enough, in fact hemp paper is already quite light and chlorine is not needed, which is essential for other types of paper
- refining consists in making the surface of the fibres rougher in order to facilitate adhesion and have a better bond
- the fibre pulp is then diluted with water to make it homogeneous
- then it is kneaded and poured over a mesh to remove the water and press it, forming the sheets of paper
- finally, the sheets obtained, still wet, are left to dry
The uses
Paper derived from hemp shives is used to make cardboard, newspapers, handkerchiefs, napkins, etc. For some particular uses where it is essential that the paper derives from fibres and has particular qualities of elasticity and resistance, hemp fibre paper is used, which is used to make cigarette paper, coffee filters, tea filter bags, filter paper for technical or scientific use, artistic paper, insulating paper for electrical use…