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Hemp Fibers and Fabrics:
The textile material used to make hemp clothing comes from the long strands of bast fiber that make up the stalk of the hemp plant. The long bast fibers are the most desirable for the manufacturing of textile. They can be spun and woven into a
fine, linen-like fabric. This fabric can then be used alone, or blended with cotton, linen, silk, or man-made fibers such as lycra and lyocell. Hemp fibers are mildew and microbe resistant, which make them valuable for the production of sails,
tarps, awnings, carpets, and clothing.
When compared to other bast fibers such as flax, ramie and jute, hemp ranks second in fiber length, ultimate fiber length, aspect ratio, tenacity, tensile strength, and breaking length, and third in cellulose content.
Flax is the dominant bast fiber in North America. The following are the primary differences between hemp and flax:
Hemp fibers can reach longer lengths although most processing methods and machinery reduce the lengths of hemp fiber. New processing techniques for hemp may be developed to enable fiber length to become an advantage in certain applications.
Flax is reported to have a "farm odor" when used in making composite board whereas hemp exhibits little odor.
A significant difference is the versatility and characteristics of hemp hurd verses flax shives. The hurd has a longer fiber than shives. This longer fiber is able to add strength to paper and perhaps other types of products.
Hemp is colorless.
Less processing is required to produce long line flax fiber of textile quality. Hemp is larger and the bonds are stronger to separate the fibers.
Flax is thinner than hemp therefore retting is easier. This is an important issue and is a critical factor affecting the quality of fiber.
Flax is preferred to hemp in the textile industry, even in geographic areas where there have no restrictions on growing hemp.
Hemp fabric is naturally more suitable to people with chemical sensitivities such as Multiple Chemical Sensitivities than cotton. Hemp grows well without herbicides, fungicides, or pesticides. The production of cotton, on the other hand,
consumes almost half of the agricultural chemicals used on American crops. Hemp bast fibers are one of the longest natural soft fibers. They are longer, stronger, more absorbent, more mildew-resistant, and more insulative than cotton. This means
that hemp will keep you warmer in winter and cooler in summer than cotton. Hemp is more effective at blocking the sun's harmful ultraviolet rays. The nature of hemp fibers makes them more absorbent to dyes, which coupled with hemp's ability to
better screen out ultraviolet rays, means that hemp material is less prone to fading than cotton fabrics are. Like cotton, hemp can be made into a variety of fabrics, including high quality linen. When blended with materials such as cotton, linen,
and silk, hemp provides a sturdier, longer lasting product, while maintaining quality and softness.
FROM FIELD TO FABRIC Hemp has demonstrated that it can have a significantly positive impact upon the environment and the lives of people. Let’s examine how friendly the processes are for converting hemp plants into fabric and garments. The
major steps in taking hemp from the field to fabric fashions are:
Growing. Hemp has been described as "Flax with attitude". It's quick growth -- germination to maturity takes between 80-120 days (depending on variety, latitude and field/climate factors) - to reach heights of up to 15' is one of
hemp's most impressive features. On a summer day, some claim that you can almost see hemp growing. Unlike cotton, hemp grows in many climate zones. It does especially well in regions where corn is grown. The plant has a short growing season of
three to four months. Hemp is grown densely packed with up to 150 plants per square meter so that tall plants containing long primary bast fibers will be produced. By the time they are ready to be harvested, the hemp plants have reached a height of
two to four meters. Hemp requires no pesticides to aid in its growth, as it is naturally pest resistant. It has been known to reduce pests in future crops when grown in rotation. Hemp requires no herbicides because it is grown so densely that it
smothers out other plants. Hemp also requires little or no fertilizer and it returns 60-70% of the nutrients it takes from the soil.
Weed Control. Herbicides are not needed for growing hemp. Hemp grows very quickly and its dense foliage chokes out most weeds. Field choice, pre-seeding tillage, shallow seeding, and packing after seeding all help to ensure that the hemp
stand will emerge quickly and uniformly to gain advantage over the weeds.
Insect Control. Bertha army worn (Mamestra configurata) may be a significant pest to industrial hemp. Bertha armyworm is a cyclical pest of canola and other crops in Canada. Other pests that have been observed include Lygus plant bugs,
cutworms, and grasshoppers. Organic farming methods can be use to control these insect pests.
Disease Control. Diseases that can attack hemp include Sclerotinia sclerotiorum and Botrytis cinerea. Wild mustard and volunteer canola, or adjacent canola stands can be the source of Sclerotinia stem rot infections. Adequate rotation with
non-susceptible crops, ensuring seed free of disease organisms, and management of host species like wild mustard and volunteer canola are the key approaches to manage disease risk. The lower plant densities used for seed production should be less
risky for sclerotinia than higher density plots for fiber production, but because fiber crops will be cut by mid-flowering the disease may be of less consequence.
Harvesting. For hemp, there are two products to be harvested – the hemp fiber and the hemp seeds. The highest quality fiber is obtained by cutting at early to mid flowering. Mowers with the crimping rolls removed and round-balers may be
suitable for low to medium quality end uses. The best approach for harvesting appears to be combining when shelling becomes evident and running the header cutter bar 4 to 5 feet above the ground. Care should be taken to avoid dehulling the seeds in
the combine, since dehulled seed is more prone to spoilage or quality loss in storage. After combining, the remaining stalk material can be cut and baled. The mature stalk contains a coarse, low-grade fiber compared with stalk cut at early
flowering, but is still marketable.
Drying and Storage. Freshly threshed seeds may have an average moisture content of 16 - 20%. The moisture content at which hemp seeds/grain can be considered "dry" is not known precisely. Seeds should be dried to between 12% and
10%. Air flow through hemp grain should be relatively free. Because the grain may be tough when it is combined, drying should commence as soon as possible after harvest to ensure that quality remains high. Large fans, some with heaters, are used to
dry the hemp seed grains.
Grain Cleaning. Ultimately hemp grain seeds need to be cleaned to a rigorous standard for food processing. Conventional seed cleaning apparatus should be able to deal with most foreign material or weed seed problems. If a significant amount
of green foreign material is present in the harvested grain, the grain should be pre-cleaned prior to storage to avoid spoilage. Some contracting companies may arrange to do the cleaning themselves.
Grading. Grading standards have not been determined for hemp grain seeds. Buyers will be concerned about foreign material, seeds with adhering bracts, dehulled or otherwise damaged seeds, and off-type crop or weed seeds.
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