Over thousands of years, humans have refined and perfected the methods to cultivate, harvest and process hemp, to obtain fibre for making garments and much more. Today, we have countless types and blends of textiles available to us, to suit all requirements and applications. But how is hemp fibre obtained and processed?
Fibre hemp is produced from low-cannabinoid varieties of Cannabis sativa L. that are planted close together to minimise branching and encourage tall, straight central stems. Unlike most psychoactive strains of cannabis, fibre varieties typically have hollow stalks, which contain far higher amounts of fibre (35% compared to 15%).
In the northern hemisphere, fibre hemp seed is planted when the ground temperature rises above 7.5°C, and is typically harvested around August, once the pollen begins to be shed. Hemp can flourish in conditions considered less than optimum, and will usually produce more than competitor crops in such instances.
However, for optimum harvests, hemp should be cultivated in mild, humid conditions, in well-drained, non-acidic soil that is high in nitrogen. Soil must be moist but not excessively so, as overly-moist soil has been shown to produce weak fibres. Cool summers are also said to assist the fibre in becoming fine and strong.
Harvesting & separating the hemp fibres
If cultivating solely for fibre, males and females are both cut down as soon as the males begin to exude pollen. If cultivating for fibre and seed, the males are allowed to pollinate the females before being cut. At this point, the females are left to mature until the seeds are ripe. Only after this are the female plants cut and the fibre and seed separated.
Interestingly, traditional farmers of hemp in the UK held that male hemp plants produce fibre much finer and silkier than that produced by the females. This was borne by a 1996 study conducted in Hungary, which concluded that male fibre was finer but female fibre slightly stronger.
Retting of hemp fibre
Once the plants have been cut, the stems are usually laid out along the ground for several weeks so that retting can occur. This is a process of decay whereby the pectin (the gel-like polysaccharide present in most plant cell walls) that binds the fibres together decomposes on exposure to light and air, and the long bast fibres are exposed. Bast fibres are those that occupy the phloem or inner bark of dicotyledonous plants such as hemp and flax.
Retting may also be done in water tanks, which speeds up the process, or in frost and snow, which is said to produce a whiter, finer fibre. Now, there are also chemical and enzymatic means with which to speed up the process of retting.
Decorticating hemp fibre
Decortication is the removal of the central woody core from the stem. This step can be performed immediately after retting, while the stems are still wet. In this case, the damp fibres are peeled off the core and then dried. Alternatively, the stems can be dried and then processed with specialised machinery, which breaks up the woody core and separates it from the fibres.
Modern decorticators often negate the need for long retting periods and separate decortication processes, instead combining the processes into one and producing ready-to-bale fibre within a few minutes of cutting the plant.
Treating the hemp fibres
Once the fibres have been separated, they are formed into bales and removed from the field to be processed into yarn. Often, the fibre is spun without further processing. However, some producers have developed chemical or mechanical processes that increase the softness or elasticity of the fibres.
For example, one involved process necessitates soaking the fibres in a near-boiling solution of soap and carbonate of soda, before being washed with water and soaked in dilute acetic acid. The fibres are washed in pure water once more, then dried and combed to produce an end result of exceptional softness and fineness.
Removing lignin from hemp fibre
Lignin is a hard, woody biopolymer that makes up 8-10% of the dry weight of hemp fibre. It is responsible for the rough, scratchy feel of traditional hemp fibre. If the lignin is removed, the resulting fibre is much smoother and softer. The inability to remove lignin from hemp without reducing its strength led to other crops being favoured over it—yet another reason that its use began to decline so dramatically in the post-industrial period.
In the mid-1980s, researchers developed a new technique to remove the lignin through enzymatic & microbial means. The protein-digesting enzyme protease is first applied to the hemp fibre, which reduces the nitrogen in the stems. Then, a species of fungus known as Bjerkandera is allowed to grow upon the fibres, where it consumes the lignin. The fibres produced with this technique were far more versatile, and hemp began to be used in garment-making once more.
Spinning hemp fibre into yarn
Hemp yarn is spun similarly to other natural fibres; typically, the fibres are twisted together to form long, continuous threads, which are often sealed with wax or a similar agent to render the end result waterproof or more durable.
It is usually at this stage of the process that other fibres are added to the blend: rather than blended cloth being woven from threads made purely from one type of fibre, the thread itself is a blend of fibres that influence its final characteristics. However, this is not always the case. Fustian, for example, traditionally referred to a textile made from a flax warp (lengthwise thread) interwoven with a cotton weft (transverse thread).
The hand-spinning process
This process was traditionally performed by hand, with the help of nothing more than two simple tools, the drop spindle and the distaff. The drop spindle is a spike-shaped weight to which the raw fibre is attached, and the distaff is a wooden stick around which the lengths of raw fibre are looped.
The hand-spinner sets the spindle spinning, and slowly releases raw fibre from the distaff; the spinning motion and the pull of the weight as it slowly drops cause the fibres to be tightly wound into threads. Some hobbyists and specialist producers still spin by hand using these traditional tools.
When hand-spinning with hemp fibres, the best choice of spindle is a lightweight top whorl, a type that can spin very fast and produce a fine, smooth yarn. Most hemp yarn is dry-spun, but can be spun ‘wet’: the spinner merely moistens the fingers with water and strokes the yarn as it spins, smoothing down the flyaway fibres to produce the smoothest possible result.
Although hemp now has to compete with an array of alternative fibres, both natural and synthetic, improved processing techniques have uncovered ground-breaking new uses for hemp textiles. As well this, the need to find textile crops of low environmental impact is increasing rapidly. For these reasons, hemp is growing in significance once more after a long period of decline, although it may never regain its former status as the number one textile crop.
Hemp textiles produced with hemp fibre
It has always been possible to make a variety of high-quality, durable fabrics from hemp, either alone or in combination with other natural fibres such as flax or silk. Although the traditional image of hemp fabric is of rough, scratchy burlap and canvas, the variety of delicate textiles that can be produced from it is remarkable.
- Linen: Linen is a good example of a lightweight textile that can be made from pure hemp. When linen is manufactured from hemp, the result is lightweight, durable and breathable – excellent in hot, humid conditions!
- Terrycloth: Hemp is also widely used to make terrycloth, the tufted material that may be either woven or knitted and is primarily used for towelling. Due to hemp’s remarkable absorptive properties, it is considered very suitable for this application.
- Twill: Hemp fibres are also very suitable for various types of twill, including denim, herringbone, and flannel, and for several types of knitted textile including jersey and velour
- Hemp silk charmeuse: When used in combination with silk, hemp can be used to make taffeta, a stiff, shiny fabric used in ball-gowns and wedding dresses. It can also be used to create charmeuse, a lustrous satin used to make figure-draping lingerie and flowing evening dresses. Even complex Jacquard-woven fabrics, in which a raised pattern is woven into the cloth, can be made with blended hemp and silk.
- Hemp cotton diapers: Hemp is often blended with cotton to make cloth diapers (nappies). It is thought to have superior absorption and durability than cotton, which is usually added to increase the softness of the fabric. Hemp also has antibacterial and antimicrobial properties, which may help to prevent nappy rash and related skin conditions.
- Hemp cotton muslin: Hemp is also blended with cotton to make fine muslin or cheesecloth, some of which can be exceptionally light and strong with excellent absorptive properties. As well as this, most knitted fabrics made with hemp are blended with cotton to improve softness.
Hemp textile is durable, versatile and fast-growing, making it a great competitor for other natural fibre plants. Most of all, it is a sustainable material to use. In a time where the world is desperately seeking sustainable alternatives, hemp textiles propose a valid and exciting opportunity.
Hemp in the mainstream fashion industry
The fashion house Ralph Lauren has used hemp-silk charmeuse produced by EnviroTextiles extensively in their garment making. Ralph Lauren has produced evening dresses and even a military-style jacket using this textile. Ralph Lauren has used several different hemp blends in recent collections too: hemp, acrylic and cotton to make jerseys, hoodies and sweatshirts; hemp and cotton to make shorts, shirts and trousers, and linen, cotton and hemp for curtains, bedclothes and upholstery.
The fact that hemp has become a mainstream fashion item is borne out by the dozens of hemp-based garments now available in high street stores such as H&M, as well as by the proliferation of high-end designer pieces, such as an Hermès cashmere, silk and hemp scarf.
As well as Ralph Lauren, EnviroTextiles fabrics have also been used by Donatella Versace, Behnaz Sarafpour, Donna Karan International, Isabel Toledo and Doo.Ri; the New York Fashion Week 2008 was a landmark year, in which many of these designers showcased their new hemp designs for the first time.
Hemp textile companies to watch
As well as EnviroTextiles, there are various other companies producing high-quality hemp fabrics: Hoodlamb, Datsusara, Patagonia, Clothing Matters, Hempy’s, Livity Outernational, Satori Movement, and, Dash Hemp, to name but a few.
Of course, fabric is just one of the few items that can be made from hemp; advances in composite plastics, building materials, foodstuffs and healthcare products are being made daily. It’s exciting to be part of an industry that has such a huge potential to make the world a little bit more eco-friendly. The applications of hemp are as versatile as sustainable.