Hemp Fabrics

History

Hemp was probably the earliest plant cultivated for textile fibre, a remnant was discovered in ancient Mesopotamia dating back to 8,000 BC. The Lu Shi, a Chinese work of the Sung dynasty (500 AD), mentions Emperor Shen Nung (28th century BC) codifying the skills needed to efficiently cultivate hemp for cloth. Renowned as the strongest natural fibre (excluding spiders’ silk), hemp fabric, made from the outer or bast fibre, is easy to produce. The plant stems are prepared by retting (rotting) in water or left in the field for the dew to break down the bonds. Then using only simple wooden tools the fibres can be separated, carded and spun. These characteristics made hemp fabric ubiquitous globally for thousands of years.

So essential was it that in 1533, King Henry VIII passed a law that all farmers had to cultivate one-quarter acre of hemp for every sixty acres of land. The requirement for hemp fabric for sails and clothes made it fundamental to the country. By 1856 the science of efficient retting processes was a staple of the learned journals of the day.

The introduction of the cotton gin into the textile industry in 1793 created a new competitor for hemp followed in 1937 by prohibition of all industrial hemp, for political reasons, an act that helped not only cotton, but nylon, flourish. Cotton, being today the dominant global natural fibre crop, is described as natural (being a plant), but its production has huge environmental impacts. The majority of clothing in the modern world is now made from synthetic, petroleum- derived plastic materials like polyester, nylon & rayon. Recent research has shown that these garments can shed micro plastics into the water system: for an average load of 6 kg, over 700,000 fibres can be released per wash.

 

Cultivation

Cotton, accounting for 78% of natural fibre production in 2012, is only cultivable in subtropical climates, which both limits the area of production and means much of it is grown where evaporation is higher, increasing water requirements further (see below).

Hemp, in contrast grows readily in most temperate or subtropical climates and is even capable of growing in climates ranging from Nepalese mountains to the equator. This allows for local production resulting in shorter transportation, less carbon thereby emitted, and thus more sustainable supply chains. Hemp productivity is more than twice as high in the same land area, with yields of up to 3 tonnes of dry fibre per hectare compared to 1.35 tonnes of cotton lint per hectare. Hemp is a low maintenance crop, being a fast growing and much more hardy plant. Overall, hemp production has an unequivocally smaller overall ecological footprint than cotton production.

 

Water

WWF studies have shown that it takes more than 20,000 liters of water to produce 1 kg of cotton, the equivalent of a single T-shirt and pair of jeans. For hemp the amount of water required is just 300-500 litres. It is estimated that approximately 73% of global cotton is harvested from irrigated areas. Worldwide, irrigation efficiency is lower than 40 per cent. The second order problems beyond stress on the water supply from irrigation of cotton include negative impacts on the regional freshwater quality including eutrophication, salinisation, pollution, wildlife contamination, raising water tables and habitat destruction

 

Chemical Farming

Cotton covers 2.5% of the world's cultivated land yet uses 16% of the world's pesticides- more than any other single major crop. Runoff from this chemical cocktail can destroy sensitive ecosystems, even if chemicals are “properly applied according to technical instructions.” The most prevalent socio-economic impacts documented with agrichemical use have been fatalities, build up of pesticides in human and animal food chains, contamination of drinking water and ground water, build up of immunity by pests, and soil mycorrhizal disruption.

Hemp meanwhile is a resilient crop, growing fast enough to outcompete weeds, tough enough to fight off pests and ideal for growing organically. Beyond this, hemp is a great rotation crop, because it leaves the land free of weeds and in good condition. Hemp is good for the soil, improving aeration and building topsoil, especially when the leaves are left to rot back. Hemp’s long taproot descends up to 2 meters in depth and these roots anchor and protect the soil from runoff. Moreover, hemp does not exhaust the soil, so hemp can be grown for many seasons successively without impacting the soil negatively.

 

Bioremediation

Hemp is suitable for growing in industrially polluted regions as it removes considerable amounts of heavy metals from the soil with its root system, helping to clean the soil.  For this reason hemp was extensively planted around Chernobyl to aid remediation. Cotton does not offer this benefit.

 

Fibre Processing

Traditionally hemp was processed by hand. After retting in the fields, simple wooden tools were used to separate the fibres, which were combed and carded by hand. All major processing stages along the cotton value chain, such as dyeing, bleaching and finishing, use large amounts of chemicals of various toxicity. Most of these chemicals, such as heavy metals, formaldehyde, azo dyes, benzidine and chlorine bleach cause environmental pollution of the mills’ waste water and many can be found as residues in the finished product. Some of them affect consumers’ health and are suspected of causing allergies, eczema or cancer. Furthermore socio- economic factors, associated with sweatshop worker impacts, can be huge. Recent studies clearly demonstrate the considerably larger energy requirement for production of synthetic fibre in comparison to hemp and cotton. Hemp represents the lowest ecological footprint of the three textiles.

 

Material Qualities

The high tensile strength of its individual fibres make hemp the strongest natural fibre apart from spiders’ silk. Hemp also has longer fibres, 1-4m, versus cotton’s c. 25-32mm. These characteristics mean hemp fabrics can be made of various strengths from light t-shirts to durable heavy canvas (which is derived from the Latin name of the plant: cannabis). Hence, hemp was used throughout seafaring history for making the sails of the ships that circumnavigated the world.

Unlike cotton, which is naturally white, hemp comes in many colours: creamy white, brown, green, grey, and even black. Furthermore it blends well with other materials and can be dyed to achieve the desired colour, both naturally and artificially. Hemp’s highly water absorbent hollow fibres also hold dyes better. Additionally hemp’s ability to withstand UV light means that once produced the garment is less susceptible to fading. The fantastic characteristics of hemp do not end there. Not only is the fibre naturally anti bacterial and mold, mildew and salt water resistant, it is avoided by moths and other insects and when organically grown is completely biodegradable.

Hemp fibre is the softest plant fiber in the world, with a beautiful drape. Hemp fabrics do not wear out but become softer with repeated use and washing. Hemp clothing is thermodynamic, meaning it buffers temperature changes. It’s hemicellulose hollow fibre means it’s cool in summer and warm in winter, as well as breathable, moisture-wicking and insulating. Many designers have worked with hemp, including Armani. Woody Harrelson wore a hemp tuxedo to the Golden Globes.

 

Conclusion

It is clear that hemp is more sustainable than cotton and that the damage of modern cotton growing and processing is a significant problem. New modern technology means hemp processing has caught up with other materials. Hemp makes materially superior fabric and clothes when compared to cotton or synthetic alternatives, but political machinations have meant that few buyers understand this. At a time when sustainability and clean industrial processes are becoming more sought after the hemp fabrics industry has the possibility of regaining its historical importance once again.

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