Thursday, June 1, 2017

Modern Hemp Cultivation

Hemp is a bast fiber plant similar to flax, kenaf, jute and ramie. Its valued primary fibers are contained around the long slender stalk that surrounds the hollow, woody core of the hemp plant called the hurd. Although hemp fiber is similar to other bast fibers, it has some major advantages such as: better strength, durability, absorbency, anti- mildew and anti-microbial properties.

Hemp is an annual plant easily grown from seed. Crops grow quickly, so many farmers can get at least 2 crops per growing season. It grows best in well-drained soil that is non-acidic and rich in nitrogen. Hemp plants also require limited pesticides because they grow so quickly and attract very few pests. In northern latitudes, hemp is usually planted between early March and late May. Hemp can grow to an average height of 6 - 14 feet in about four months of growth.

Farmers can tell when the crop is ready for harvesting when the plants begin to shed pollen... usually in mid-August for North America. Harvesting for seed occurs four to six weeks later. High quality hemp fiber is normally ready for harvest about 70-90 days after planting.

Once the crop is cut, the stalks are allowed to rett (removal of the pectin [binder] by natural exposure to the environment) in the field for four to six weeks, weather permitting, to loosen the fibers. While the stalks lay in the field, the leaves decompose allowing the nutrients to return to the soil. The stalks are turned several times and then baled with hay harvesting equipment. The bales must be stored in dry places to keep the moisture away from the hemp stalks. A hemp fiber crop typically yields from 2-6 short tons of dry stalks per acre, or 3-5 short tons of baled hemp stalks per acre.

To get the fiber from the hemp plant, a special machine called a decorticator is used. It has rows of independent teeth and a chopper that pulverizes the stock into fine hair-like fiber. When harvesting hemp for textiles, specialized cutting equipment is required so the machine doesn’t get tangled up with the bast fiber.

The core fiber of the hemp plant is also used. It is called the hurd, which is the middle part, the wood-like core, of the hemp and kenaf plant. It is a highly absorbent material that has many useful properties. A study done by the Navy showed that the core material of hemp and kenaf is one of the most absorbent materials on the planet.

It is twice as absorbent as wood shavings, making it an excellent animal bedding and garden mulch. It also can be blended with lime to create a strong, yet lightweight concrete or plaster sometimes called “hempcrete”. Its high cellulose content also means it can be applied to the manufacturing of plastics, avoiding petroleum used for many products. Like the primary bast fiber, it is biodegradable and has anti-mildew and anti-microbial properties.

Hemp Fabrics and Fibers

Hemp has been used as clothing fiber for at least 10,000 years. Traditional methods for turning hemp fiber into fabric are eco- friendly, and today many companies still use those methods. Hemp is one of the strongest and most durable of all fibers; it holds its shape well, and it does not require herbicides or pesticides to produce. It is also antimicrobial to protect your skin better.

Once the world’s most ubiquitous fiber crop, hemp has largely been replaced by cotton and other fibers, both natural and synthetic. However, renewed interest in the hemp industry is opening the possibility for new hemp textiles to be produced.

Ancient history has shown us that it has always been possible to make a variety of high-quality, durable fabrics from hemp, either alone or in combination with other natural fibers such as flax or silk. 

Although traditionally hemp fabric is rough and sort of scratchy, there are a variety of remarkable delicate textiles that can be produced from hemp.

Linen is a lightweight textile that can be made from pure hemp. Although ‘linen’ refers strictly to cloth made from flax fibers, the standard linen weave is used with other fibers; the resulting textiles are all generally known as linens. Cloth made from hemp is lightweight, durable and breathable, and is excellent in hot, humid conditions.

Hemp is also widely used to make terrycloth, a towel like fabric primarily used as an absorbent. When used in combination with silk, hemp can be used to make taffeta fabric that’s used in ball-gowns and wedding dresses. It can also be made into a charmeuse, a lustrous satin that is fabulous for figure- draping lingerie and flowing evening dresses.

Hemp is often blended with cotton to make cloth diapers because of its superior absorption and durability qualities and the increase in the softness of the fabric. Because hemp is antibacterial and antimicrobial, it helps prevent diaper rash and related skin conditions in babies. Basically most knitted fabrics, when blended with hemp, have improved softness.

Antibacterial Properties of Hemp Fiber

Lab tests showed that hemp fabric helps kill the ‘staph’ bacteria (staphylococcus aureus). Researchers studied the growth of the bacteria on a textile made from a blend of 60% hemp fiber and 40% rayon, and discovered that 98.5% of the bacteria had died by the time of first testing. The same textile was also infected with Klebsiella pneumonia, and was 65.1% effective in killing the bacteria at first testing.

Fabrics made from hemp could be very beneficial for the healthcare industry. Scrubs made with hemp material could help keep bacteria from spreading from one patient to the next and protect the wearer from dangerous bacteria infection. Touching towels, sheets or clothing previously handled by an infected person often transmits staph infections. MRSA (Methicillin-resistant staphylococcus aureus) a deadly bacteria people get in the hospital, is estimated to kill 19,000 people each year in the USA alone. Making fabrics from hemp for hospitals could help keep those nasty germs at bay.

The company responsible for manufacturing the fabric used in this test was EnviroTextiles, whose lead textile engineer, Barbara Filipponne, began working with Chinese hemp in the early 1990’s. Now, EnviroTextiles has over a hundred different pure and blended hemp textiles, several of which have been added to the USDA’s BioPreferred Program (a preferred procurement program for Federal agencies and contractors).

Ralph Lauren has used hemp-silk charmeuse produced by EnviroTextiles to make various garments including evening dresses. They have also used several different hemp blends in recent collections such as: 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.

Hemp 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.