Linen

30 06 2010

Linen is a textile made from the fibers of the flax plant, Linum usitatissimum L., which is a delicate and graceful annual that stands about 3 feet high and produces attractive blue flowers. Its Latin name means “most useful,” and for good reason. Though technically a wildflower, flax  has been cultivated for thousands of years for a wide variety of important uses.  Common flax was one of the earliest domesticated plants.  A cousin of hemp, cannabis sativa L., flax is also known as a “bast” plant, meaning the fiber is collected from the inner bark, or bast,  of the steam. 

Flax  grows best at northern temperate latitudes, in cool,  humid climates and within moist, well-plowed soil.

Today, France, Belgium, Netherlands, Spain, Russia, Egypt and China are the foremost producers of flax for commercial textile purposes.   China is also a major buyer of raw flax for processing, with imports of 60 000 tons a year, including most of Europe’s flax fibers. Bulk linen production has shifted to Eastern Europe and China, but niche producers in Ireland, Italy and Belgium continue to supply the market for high quality fabrics in Europe, Japan and the USA.

There are two main types of flax grown worldwide:  fiber flax and seed flax.

FIBER FLAX:

Flax is one of the oldest fiber crops in the world.  It was used by the ancient Egyptians, Romans, Greeks and Hebrews for food, clothing and medicine.

The use of flax fiber in the manufacturing of cloth in northern Europe dates back to Neolithic times. In North America, flax was introduced by the Puritans, and today has become an essential commercial crop grown throughout the Midwest.

Today, flax is used to make linen cloth,  and it’s usually an expensive textile, produced in relatively small quantities.  Linen fabric maintains a strong traditional niche among high quality household textiles – bed linen, furnishing fabrics, and interior decoration accessories.  More than 70% of linen goes to clothing manufacture, where it is valued for its exceptional coolness in hot weather – the legendary linen suit is a symbol of breezy summer elegance.

Linen has a long staple (i.e., individual fiber length).  The best grades of flax  are used for fine fabrics such as damasks, lace and sheeting. Shorter flax fibers produce heavier yarns suitable for kitchen towels, sails, tents and canvas.  Lower fiber grades are used as reinforcement and filler in thermoplastic composites and resins used in automotive interior substrates, twine, rope,  furniture and other consumer products.  Flax fiber is also a raw material for the high-quality paper industry for the use of printed banknotes and rolling paper for cigarettes and tea bags.   Linen fabric is one of the preferred traditional supports for artists canvas. In the United States cotton is popularly used instead because linen is many times more expensive, restricting its use to professional painters. In Europe however, linen is usually the only fabric support available in art shops. Linen is preferred to cotton for its strength, durability and archival  integrity.

SEED FLAX:

Flax seed is grown for human and animal consumption. Flax seeds can be eaten raw or cooked, cracked or whole, and can be ground into flour. They are often sprinkled on top of bread, cooked into foods like chips, muffins and cakes or added to granola cereal. Flax seeds contain high amounts of Omega-3, 6 and 9 fatty acids, which are believed to reduce cholesterol, boost the immune system and lower the risk of heart disease. They also contain potassium, magnesium, fiber and protein, and make a good natural laxative.                    

Flax seed oil (also called linseed oil) is used for culinary as well as industrial purposes.  A good source of essential omega-3 fatty acids, the oil is believed to provide benefits to arthritis and lupus patients by reducing inflammation.   For industry, it serves as a pigment binder for oil paint and a drying agent for paints, lacquers and inks. It is sometimes used as a wood finish, in varnishes, printing inks, and soaps and can be combined with cork to make linoleum.

Once oil is cold pressed from flax seeds, the husks, which are high in protein,  are often used as feed for chickens and other livestock. The seeds provide animals with much needed fiber and protein. Eggs from chickens that were fed flax seeds are  purported to be high in omega fatty acids and have added health benefits.

Flax  fibers range in length up to 90 cm, and average 12 to 16 microns in diameter.  They are not as long as hemp, which has fibers that measure from 90 cm to 460 cm, yet they are much longer than cotton fibers, which measure only as much as 3.5 cm.
Harvesting:

There are three degrees in the ripening of the flax grown to make linen: green, yellow and brown. The yellow has proved to be the most suitable for fiber production. Flax that is pulled too early – green – produces very fine but weak fibers. On the other hand, in overripe flax – brown – the stems are strong but brittle and produce too high a proportion of undesirable short fibers (‘tow’). When the flax is yellow, the fibers are long and supple, and therefore ideal for further processing.  (This is where we get the term “flaxen” to describe a yellow haired person.) The plant must be harvested as soon as it appears ready since any delay results in linen without the prized luster.  It is important that the stalk not be cut in the harvesting process but removed from the ground intact; if the stalk is cut the sap is lost, and this affects the quality of the linen.

These plants are often pulled out of the ground by hand, grasped just under the seed heads and gently tugged. The tapered ends of the stalk must be preserved so that a smooth yarn may be spun. The stalks are tied in bundles (called beets) and are ready for extraction of the flax fiber in the stalk. However, fairly efficient machines can pull the plants from the ground as well.

Once the plants have been harvested, the fibers must be released from the stalk.  This process is called “retting” – actually a process of rotting away the woody bark of the plant which also loosens the pectin or gum that attaches the fiber to the stem:

  • Retting may be accomplished in a variety of ways. In some parts of the world, linen is still retted by hand, using moisture  to rot  away the bark. The stalks are spread on dewy slopes, submerged in stagnant pools of water, or placed in running streams. Workers must wait for the water to begin rotting or fermenting the stem—sometimes more than a week or two. However, most manufacturers today use chemicals for retting. The plants are placed in a solution either of alkali or oxalic acid,  then pressurized and boiled. This method is easy to monitor and rather quick, although some believe that chemical retting adversely affects the color and strength of the fiber and hand retting produces the finest linen. Vat or mechanical retting requires that the stalks be submerged in vats of warm water, hastening the decomposition of the stem. The flax is then removed from the vats and passed between rollers to crush the bark as clean water flushes away the pectin and other impurities.
  • If flax is not fully retted, the stalk of the plant cannot be separated from the fiber without injuring the delicate fiber. Thus, retting has to be carefully executed. Too little retting, or under retting,  may not permit the fiber to be separated from the stalk with ease; it produces a coarse yarn suitable only for ropes.  Too much retting (over retting or rotting) will weaken fibers so they will have limited application.  The value of a batch can vary by 100% depending on the quality of the retting.
  • After the retting process, the flax plants are squeezed and allowed to dry out before they undergo the process called breaking. In order to crush the decomposed stalks, they are sent through fluted rollers which break up the stem and separate the exterior fibers from the bast that will be used to make linen. This process breaks the stalk into small pieces of bark called shives. Then, the shives are scutched. The scutching machine removes the broken shives with rotating paddles, finally releasing the flax fiber from stalk.
  • The fibers are now combed and straightened in preparation for spinning. This separates the short fibers (called tow and used for making more coarse, sturdy goods) from the longer and more luxurious linen fibers. The very finest flax fibers are called line or dressed flax, and the fibers may be anywhere from 12-20 in (30.5-51 cm) in length, but first class fibers are at least 60 cm.   Color of light grey, steel grey and silver grey are considered the best.

Spinning:

  • Line fibers (long linen fibers) are put through machines called spreaders, which combine fibers of the same length, laying the fibers parallel so that the ends overlap, creating a sliver. The sliver passes through a set of rollers, making a  roving which is ready to spin.
  • The linen rovings, resembling tresses of blonde hair, are put on a spinning frame and drawn out into thread and ultimately wound on bobbins or spools. Many such spools are filled on a spinning frame at the same time. The fibers are formed into a continuous ribbon by being pressed between rollers and combed over fine pins. This operation constantly pulls and elongates the ribbon-like linen until it is given its final twist for strength and wound on the bobbin. While linen is a strong fiber, it is rather inelastic. Thus, the atmosphere within the spinning factory must be both humid and warm in order to render the fiber easier to work into yarn. In this hot, humid factory the linen is wet spun in which the roving is run through a hot water bath in order to bind the fibers together thus creating a fine yarn. Dry spinning does not use moisture for spinning. This produces rough, uneven yarns that are used for making inexpensive twines or coarse yarns.
  • These moist yarns are transferred from bobbins on the spinning frame to large take-up reels. These linen reels are taken to dryers, and when the yarn is dry, it is wound onto bobbins for weaving or wound into yarn spools of varying weight. The yarn now awaits transport to the loom for weaving into fabrics, toweling, or for use as twine or rope.

A great concern to the environment is the chemicals used in retting. These chemicals must be neutralized before being released into water supplies. The stalks, leaves, seed pods, etc. are natural organic materials and are not hazardous unless impregnated with much of the chemicals left behind in the retting process. The only other concern with the processing of linen is the smell—it is said that hand-retted linen produces quite a stench and is most unpleasant to experience.

The first flax-spinning mill was opened in England in 1787, but only in 1812 was linen successfully woven with power looms. The linen industry suffered in relation to cotton because many textile inventions were not applicable to linen.   Although linen exceeds cotton in coolness, luster, strength, and length of fiber, the expense of production limits its use.

The decrease in use of linen may be attributed to the increasing quality of synthetic fibers, and a decreasing appreciation of buyers for very high quality yarn and fabric. Very little top-quality linen is produced now, and most is used in low volume applications like hand weaving and as an art material.

Over 90% of the world’s spinning equipment are designed to quickly and effectively spin fibers based on the length and diameter of cotton fibers.  This is referred to as the “cotton” system.  No other spinning system is as productive or cost-effective as the cotton system.  Flax fibers can be broken down into their shortest components, and this is called cottonization and the product is called cottonized flax.  Flax has traditionally been cottonized using mechanical systems (i.e., mechanical cottonization) but it can also be done using enzymes, steam explosion and ultra-sound.  This “cottonization” is done to be able to spin linen fibers on cotton machines – it means the process is quicker and requires less equipment.  However, the finished fibers often lose the characteristic linen look.

The Living Linen Project was set up in 1995 as an Oral Archive of the knowledge of the Irish linen industry still available within a nucleus of people who were formerly working in the industry in Ulster.  There is a long history of linen in Ireland.

For those of you with linguistic interests, linen has given rise to a number of words:

  • line, derived from the use of a linen threadto determine a straight line;
  • liniment, due to the use of finely ground flax seeds as a mild irritant applied to the skin to ease muscle pain
  • lining, because linen was often used to create a lining for wool and leather clothing
  • lingerie, via French, originally denotes underwear made of linen
  • linseed oil, an oil derived from flaxseed
  • linoleum, a floor covering made from linseed oil and other materials

CHARACTERISTICS of Linen:

Linen is among the strongest of the vegetable fibers, with 2 to 3 times the strength of cotton.  It is a very durable, strong fabric, and one of the few that are stronger wet than dry. It is smooth, making the finished fabric lint free, and gets softer the more it is washed.  The fibers  are resistant to damage from abrasion.

However, constant creasing in the same place in sharp folds will tend to break the linen threads. This wear can show up in collars, hems, and any area that is iron creased during laundering. Linen has poor elasticity and does not spring back readily, explaining why it wrinkles so easily.

Linen fabrics have a high natural luster; their natural color ranges between shades of ivory,  ecru,  tan, or grey. Pure white linen is created by heavy bleaching. Linen typically has a thick and thin character with a crisp and textured feel to it, but it can range from stiff and rough, to soft and smooth.

When freed from impurities, linen is highly absorbent and will quickly remove perspiration from the skin. Linen is a stiff fabric and is less likely to cling to the skin; when it billows away, it tends to dry out and become cool so that the skin is being continually touched by a cool surface.  It’s valued for its exceptional coolness and freshness in hot weather.

Mildew, perspiration, and bleach can also damage the fabric, but it is resistant to moths and  carpet beetles. Linen is relatively easy to take care of, since it resists dirt and stains, has no lint or pilling tendency, and can be dry cleaned, machine washed or steamed. It can withstand high temperatures, and has only moderate initial shrinkage.

Linen should not be dried too much by tumble drying: it is much easier to iron when damp. Linen wrinkles very easily, and so some more formal linen garments require ironing often, in order to maintain perfect smoothness. Nevertheless the tendency to wrinkle is often considered part of the fabric’s particular “charm”, and a lot of modern linen garments are designed to be air dried on a good hanger and worn without the necessity of ironing.

A characteristic often associated with contemporary linen yarn is the presence of “slubs”, or small knots which occur randomly along its length. In the past, these slubs were considered defects associated with low quality. The finest linen had very consistent diameter threads, with no slubs.  Today, however, the presence of slubs is considered appealing, and fashion dictates that even the finest linens have these slubs.

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Cotton

24 06 2010

King Cotton.  The cotton textile industry has perhaps been studied as much as any industry in history, and the fiber itself is so important that it’s traded as a commodity.  “In high cotton” means to be wealthy, somebody can be out of his “cotton picking mind”, and  “to cotton” has even become a verb!  Today the range of uses for cotton has expanded so much (only 35% of the global harvest ends up in textiles) and there are so many issues surrounding cotton – from government subsidies, to GMO cotton to the intense chemical cultivation needed to produce conventional cotton – that I want to say at the outset that I just want to discuss  cotton without putting a value judgment on the plant, which after all is a pretty incredible natural gift to us!

Cotton is the world’s most popular natural fiber.    The fruit of the plant, better known as the cotton boll,  provides the fiber – the fiber of a thousand faces and almost as many uses, the fibers which the ancients called “white gold” because it was so valuable. 

Successful cultivation of cotton requires a long frost-free period, plenty of sunshine, and moderate rainfall, usually from 600 to 1200 mm (24 to 48 inches).  In general, these conditions are met within the seasonally dry tropics and subtropics in the Northern and Southern hemispheres, but  lots of the cotton grown today is cultivated in areas with less rainfall than cotton needs, so 70% of cotton crops are irrigated.

Today, cotton is cultivated in around 130 countries – but only six countries (China, Brazil, India, Pakistan, the USA and Uzbekistan) account for more than 80% of total production.  It is one of the world’s most widely produced crops and uses about 2.5% of the world’s arable land area.  Cotton cultivation is fundamental to the economies of many developing countries; according the International Cotton Advisory Committee (ICAC), around 20 million farms depend on cotton.

Cotton fibre grows on the seed of a variety of plants of the genus Gossypium, a member of the Hibiscus family. Of the four cotton species cultivated for fibre, the most important are :

  • G. hirsutum (also known as Upland cotton or Mexican cotton), which originated in Mexico and produces 90% of the world’s cotton.  Upland cotton is white, 2.1 – 3.2 cm long.
  • G. barbadense (also known as Pima cotton), of Peruvian origin, which accounts for 5% of the world’s cotton.  Pima cotton is longer than Upland, 3.5 – 4.1 cm, and more costly.  Special features of Pima cotton are its luster and extreme softness. Types of Pima cotton:
    • Egyptian cotton is 3.8 to 4.4 cm long, yellow brown in color, and grown only in Egypt.
    • Sea Island, longest of all the cotton fibers (3.5 to 6.4 cm) and the most expensive.  Yellow in color.  Grown in SC and GA coast.

All parts of the cotton plant are useful.  When seed cotton is ginned, more seed than fiber is produced.  For every kilogram of fibre produced, each cotton plant  produces 1.65 kg of seed.  The cottonseed is crushed in order to separate it into its three products – oil, meal and hulls. Cottonseed oil (about 20% of the harvested plant) is used primarily for shortening, cooking oil and salad dressing and in lots of snack foods. The meal and hulls that remain are very high quality proteins, and  are used either separately or in combination as livestock, poultry and fish feed and as fertilizer.  We do not think of cotton as a potential source of food, and for good reason. The seeds of the cotton plant are rife with a potent poison called gossypol that attacks both the heart and liver. Only the multi-chambered stomachs of cattle and other hooved animals can cope with this poison, relegating cottonseed to a role as animal feed.

The fiber, or lint, which is used in making cotton cloth is almost pure cellulose. Linters – the short fuzz on the seed – provide cellulose for making plastics, explosives and other products. Linters also are incorporated into high quality paper products and processed into batting for padding mattresses, furniture and automobile cushions.  As a refined product, cotton linters have medical, cosmetic and other uses.

Cotton planting, harvesting and spinning can be done in a highly mechanized way – or it can be done entirely by hand.  Only about 30% of the world’s cotton production is harvested by machines.  Conventional cotton stripping machines use rollers equipped with alternating bats and brushes to knock the open bolls from the plants into a conveyor.

A second kind of stripper harvester uses a broadcast attachment that looks similar to a grain header on a combine. All harvesting systems use air to convey and elevate the seed cotton into a storage bin referred to as a basket. Once the basket is full, the stored seed cotton is dumped into a boll buggy, trailer or module builder.

Today, nearly all cotton is stored in “modules”, which look like giant loaves of bread. Modules allow the cotton to be stored without loosing yield or quality prior to ginning. Specially designed trucks pick up modules of seed cotton from the field and move them to the gin.

Modern gins place modules in front of machines called module feeders. Some module feeders have stationary heads, in which case, giant conveyors move the modules into the module feeder.  The module feeders literally break the modules apart and “feed” the seed cotton into the gin. Once in the cotton gin, the seed cotton moves through dryers and through cleaning machines that remove the gin waste such as burs, dirt, stems and leaf material from the cotton. Then it goes to the gin stand where circular saws with small, sharp teeth pluck the fiber from the seed.

From the gin, fiber and seed go different ways. The ginned fiber, now called lint, is pressed together and made into dense bales weighting about 500 pounds.  Producers usually sell their cotton to a local buyer or merchant who, in turn, sells it to a textile mill either in the United States or a foreign country.

The seed usually is sold by the producer to the gin. The ginner either sells the seed for feed or to an oil mill where the linters (a byproduct of the oil mill – don’t confuse this with the ginned fiber, called lint) are removed in an operation very much like ginning. Linters are baled and sold to the paper, batting and plastics industries, while the seed is processed into cottonseed oil, meal and hulls.

At the textile mill, the bales are opened by machines, and the lint is mixed and cleaned further by blowing and beating. The short lint that comes out usually is separated and sold for use in other industries. The best part of the lint consists of fibers about 1 inch to 1 ¾ inches long.

The mixed and fluffed-up cotton goes into a carding machine which cleans the fibers some more and makes them lie side by side. The combing action of the carding machine finishes the job of cleaning and straightening the fibers, and makes them into a soft, untwisted rope called a sliver (pronounced sly-ver).

On modern spinning frames, yarn is made directly from the sliver. The spinning devices take fibers from the sliver and rotate it up to 2,500 revolutions in a second twist that makes fibers into a yarn for weaving or knitting into fabrics.

After all of that,  the yarn is ready to be woven into fabric.

Cotton, as an intensely studied commodity, has a variety of grades, usually dependent on the length of the cotton staple fibers.  Cotton quality is judged based on the grade, color, length of the fibers and the character:

  • Grade: determined by the major or minor brightness of the fibers, by the more or less white color and the presence of particles of the leaf or other extraneous substances.
  • Color: color can differ greatly, from white to grey, but also reddish, tawny, chamois colored varieties.
  • Length: the most important attribute, and this category is divided into two parts:
    • Long fiber (long staple) measures more than 28 mm
    • Short fiber (short staple) does not reach the length of 18 mm; an intermediate category of 18 – 28 mm (such as the US Uplands cotton) constitutes 60% or more of world production
  • Character or micronaire: partly connected with origin, variety and maturity but a cotton of good character is that whose fibers are the most strong and robust (so as to resist traction and breakage); homogenous and uniform (to produce few losses in working) and have a complete physical-chemical constitution (so as to give the cotton mass notable solidity and compactness, smoothness and silkiness).  Cotton fiber fineness is defined as mass per unit of length,  the term millitex (for milligram per kilometer) is used; and upland cottons have millitex values between 150 and 200.  Ideal maturity ratios are around 0.8

The traditional method of establishing cotton quality is by visual hand classing. Professional classers hand class bale by bale and visually define color, grade, leaf content, preparation, maturity, and incidence of defects. In other words, the overall visual characteristics of the cotton is sampled. In addition, the classers randomly pull the staple to evaluate the length of the fibers.

A certain degree of subjectivity is involved in this method of classifying cotton. Samples are judged against grade boxes that are produced to establish standards. The Universal Standards, established each year by the USDA, define standards: Good Middling, Strict Middling, Middling, Strict Low Middling, Low Middling, Strict Good Ordinary, Good Ordinary. Other terms that are used to describe variations in color include: Light Spot, Spotted, Tinged, Grey, Dull, etc. Inferior cotton is denominated as Below Grade. Specific machines are then used randomly, as a complement, to measure micronaire and strength (Pressley). Cotton negotiated under this methodology is referred to as ‘sold on description’.

The more modern method of ascertaining quality is with a High Velocity Instrument (HVI). With these machines more than 1000 samples can be tested per day. These machines are generally not as accurate as hand classing with respect to color, grade and leaf, however, the results are more objective and very effective for measuring, staple, strength, uniformity, short fiber content and elongation which have gained much more importance. These machines do not have the capability of measuring the overall preparation of the cotton. Nonetheless, the trend is for textile mills to require HVI results when purchasing cotton.

CHARACTERISTICS:

Cotton fabrics are very comfortable to wear due to their soft hand, lovely drape and other characteristics.  They are easy to handle and sew.

Cotton has excellent absorbing capabilities.  “Absorbent” cotton will retain 24-27 times its own weight in water and is stronger  wet than dry. This fiber absorbs and releases perspiration quickly, thus allowing the fabric to “breathe”.

Cotton can stand high temperatures and takes dyes and printing inks easily.

Cotton is washable but does shrink if it has not been treated with a shrink resistant finish.  Boiling and sterilizing temperatures can also be used on cotton without disintegration.  Colored cotton garments retain their color longer if they are washed in warm or cool water. Cotton fabrics can be bleached but too much bleaching could weaken the fibers.  Sunlight  harms cotton by causing it to oxidize and turn yellow.

Cotton wrinkles very easily, but can be ironed at relatively high temperatures. However, there are many cotton garments on the market that have been treated with wrinkle resistant finishes or blended with polyester to give it wash and wear properties..

Mercerized cotton is treated to permanently straighten the cotton fibers which then becomes a smooth, rod-like fiber that is uniform in appearance with a high luster.





Silk

16 06 2010

Silk has set the standard in luxury fabrics for several millennia. Silk is highly valued because it possesses many excellent properties. Not only does it look lustrous and feel luxurious, but it is also lightweight, resilient, and extremely strong— the strongest natural fiber known to man, one filament of silk is stronger then a comparable filament of steel! Although fabric manufacturers have created less costly alternatives to silk, such as nylon and polyester, silk is still in a class by itself.

The origins of silk date back to ancient China. Legend has it that a Chinese princess was sipping tea in her garden when a cocoon fell into her cup, and the hot tea loosened the long strand of silk. Ancient literature, however, attributes the popularization of silk to the Chinese Empress Si-Ling, to around 2600 B.C. Called the Goddess of the Silkworm, Si-Ling apparently raised silkworms and designed a loom for making silk fabrics. Silk was originally reserved exclusively for the use of the emperor; gradually silk came into more general use.   Silk, indeed, rapidly became one of the principal elements of the Chinese economy. Silk was used for musical instruments, fishing-lines, bowstrings, bonds of all kinds, and even rag paper, the word’s first luxury paper. Eventually even the common people were able to wear garments of silk.

During the Han Dynasty, silk ceased to be a mere industrial material and became an absolute value in itself. Farmers paid their taxes in grain and silk. Silk began to be used for paying civil servants and rewarding subjects for outstanding services. Values were calculated in lengths of silk as they had been calculated in pounds of gold. Before long it was to become a currency used in trade with foreign countries.

For more than two thousand years the Chinese kept the secret of silk altogether to themselves. It was the most zealously guarded secret in history. Indeed, the reigning powers decreed death by torture to anyone who divulged the secret of the silk-worm. Eventually, the mystery of the silk-making process was smuggled into neighboring regions, reaching Japan about A.D. 300 and India around A.D. 400.

The first country to apply scientific techniques to raising silkworms was Japan, which produces some of the world’s finest silk fabrics. Other countries that also produce quality silks are China, Italy, India, Spain, and France. China was the largest exporter of raw silk in the early 1990s, accounting for about 85% of the world’s raw silk, worth about $800 million. Exports of China’s finished silk products were about half of the world’s total at about $3 billion.

Silk has a miniscule percentage of the global textile fibre market—less than 0.2%. This figure, however, is misleading, since the actual trading value of silk and silk products is much more impressive. This is a multibillion dollar trade, with a unit price for raw silk roughly twenty times that of raw cotton. (The precise global value is difficult to assess, since reliable data on finished silk products is lacking in most importing countries.)

“With time and patience the mulberry leaf becomes a silk gown”

Ancient Chinese Proverb.

The finest, most desirable silk comes from the mulberry silkworm, which is actually a caterpillar and not a worm. Blind and flightless, it feeds solely on the leaves of mulberry trees.  Known as the Bombyx mori, the mulberry silk worm is a fascinating but tragic bundle of insect life. Raised by professional keepers in China on trays of mulberry leaves a thousand years before the Roman Empire when wild tribes were roaming Europe living in stick and mud huts, the mulberry silkworm has been totally domesticated and can not live without humans for their care and feeding. There are no wild silkworms or Bombyx mori moths that roam and feed in the wild.

The cultivation of silkworms for the purpose of producing silk is called sericulture.  Over the centuries, sericulture has been developed and refined to a precise science. Today, a hugely developed industry has developed around the raising of silkworms for the production of silk. Silk worms are raised by large corporate silk worm farmers and hobbyists all over the world. Sericulture companies sell and ship all that the silk grower enthusiast needs from Bombyx mori ova (silkworm eggs) in an incubation dish to handling tools.

One acre of mulberry trees produces enough foliage to feed silkworms that create 178 pounds of cocoons which can be unraveled into 35 pounds of raw silk. The mulberry leaves are a renewable and sustainable crop as the trees produce year after year. One mature mulberry tree will produce enough foliage for 100 silkworms. Generally, one cocoon produces between 1,000 and 2,000 feet of silk filament, made essentially of two elements: a substance, called fibroin, makes up between 75 and 90% of the filament, and sericin, the gum secreted by the caterpillar to glue the fiber into a cocoon, comprises about 10-25%. Other elements include fats, salts, and wax. One silkworm produces very little useable silk.  To make one yard of silk material, about 3,000 cocoons are used.

The natural course in the cycle of worm to moth would be for the chrysalis to break through the protective cocoon and emerge as a moth. But by breaking its way out, it cuts this fiber off in many places, thus largely decreasing its value;  So, sericulturists must destroy the chrysalis so that it does not break the silk filament. This is done by stoving, or stifling, the chrysalis with heat.  The usual method is that of immersing the cocoons in steam for a few minutes. Another method, that of placing the cocoons in boiling water, serves a double purpose. Not only does it kill the chrysalides, but it also softens the seracin, the “gum”  that sticks the threads together, so that they can be unreeled from the cocoon.  Although silk is about 20% seracin, only about 1% is removed at this point.

Reeling the filament

  • Reeling may be achieved manually or automatically. The cocoon is brushed to locate the end of the fiber. The method is as simple as it is laborious.  It is threaded through a porcelain eyelet, and the fiber is reeled onto a wheel. Meanwhile, diligent operators check for flaws in the filaments as they are being reeled.
  • As each filament is nearly finished being reeled, a new fiber is twisted onto it, thereby forming one long, continuous thread. Sericin contributes to the adhesion of the fibers to each other. s. The average cocoon reels off about three hundred yards in a single thread.

Packaging the skeins

This is raw silk, just pure silk fibers without any chemicals or treatments added, although sometimes the raw silk fibers will be soaked in a 1% hydrogen peroxide solution for a few hours to refine the creamy color. Organic and sustainable certification organizations are working on standards for organic silk but they have not yet been finalized and adopted.

Degumming

The remaining sericin, or silk “gum”,  must be removed from the yarn by soaking it in warm soapy water.  This is called degumming, and it improves the sheen, color, hand and texture of the silk.  Because the gum can serve as a protective layer, it is usually left on the silk until it’s ready to dye.  But the degumming process,  which enables the silk to accept dyes readily and which contributes  to its high gloss,  also causes the silk to lose about 25% of its weight and not a little strength. If the scouring and bleaching are not well and carefully done, the reduction in strength may be serious indeed.

Finishing silk fabrics

  • After degumming, the silk yarn is a creamy white color. It may next be dyed as yarn, or after the yarn has been woven into fabric.   After dyeing, the skeins are again dried, run through an equalizing machine similar to a stretcher, and then rewound into the form in which they are wanted by consumers and the trade, such as spools, bobbins, skeins, etc.
  • This completes the process of silk throwing. The silk is now ready for the weaver, the knitter, the lace maker, or the embroidery maker.

After the raw silk has been reeled into skeins or hanks, the most laborious parts of silk production are completed; that is, most of the work done on the fiber thereafter is done by machine processes instead of by hand. The amount of hand labor that it takes to produce raw silk is almost incredible, and the amount of labor taken after the machine processes begin is no less than for other textiles. It has been said that it takes more human labor to produce a lady’s silk dress, from the mulberry leaves into the finished product ready for wear, than it takes to produce and build a locomotive out of the raw ores in the ground. More hours are expended, and more people have something to do with the work.  If the laborers employed in the production of silk were paid as high wages as are commonly paid in the iron and steel industry the silk dress would cost almost as much as that locomotive. As it is, raw silk production is carried on chiefly in countries where wages are very low. At the present prices of silk, the most efficient workmen doing their very best could not earn more than fifteen cents per day at this kind of work.

WEIGHTED SILK:

Silk is sold by weight.  “Weighting” is a textile manufacturing practice peculiar to silk manufacturing and involves the application of metallic salts to add body, luster and physical weight to silk fabric. The reason for adding metals to silk fabric is to increase the weight of the fabric and, because silk fabric sells by the pound, the extra weight increases the selling price of the fabric. Generally, only the finer and more expensive reeled silks are weighted rather than the less costly spun silks By means of weighting the manufacturer can increase the weight of silk by 3 to 4 times.

Weighting is done by immersing the silk  in a solution rich in tannin, then transferred to iron or tin baths, then washed.   Weighting causes the fabric to lose its strength as soon as the weighting is applied. Heavily weighted silk must be made into garments as soon as it is made. Spots develop in the dyes. Saltwater, perspiration and tears cause spots to be formed which seems as if the silk is eaten by acids. Sunlight also attacks weighted silk and can cause silk to fall to pieces.

The silk industry makes a distinction between pure-dye silk and  weighted silk. In the pure-dye process, the silk is colored with dye, and may be finished with water-soluble substances such as starch, glue, sugar, or gelatin.  But it is not weighted.    If weighting is not executed properly, it can decrease the longevity of the fabric by causing it to lose much of its strength and durability, so pure-dye silk is considered the superior product.  Also, the metallic salts used to weight silk can cause health risks and problems for some people.

After dyeing, silk fabric may be finished by additional processes, such as bleaching, embossing, steaming, or stiffening.

WILD SILKS:

The wild silks are gathered principally in Japan, China; and India. There are several varieties of wild silk cocoons, each with qualities somewhat different from the rest. The principal variety of Japan is the Yamai-mai, and the chief varieties of India are the tusser, or tussah, and the ailanthus. Most of these silks are much darker in color than the domesticated silk, the Bombyx mori, probably because of the difference in feed. Wild silkworms do not always have mulberry leaves to eat. Great numbers feed on oak leaves and in some cases on other plants.

In  general,  it may be said that wild silks are in most respects of poorer quality than domesticated silk. They are harder to bleach, and do not take dyes so well. They are generally very uneven in texture, but when made up into fabrics are often more durable than common silks. Wild silks are used principally in the manufacture of pile fabrics such as velvet, plush, and imitation sealskin, and in heavy or rough cloths such as pongees and shantungs. While the silkworms of the wild varieties take care of themselves, and therefore do not require the constant labor that must be given to domesticated silk, the expense of gathering is nevertheless high. The wild cocoons must be hunted, trees must be climbed to gather them, and much time may be consumed in collecting comparatively few. On the whole, however, because of the poorer qualities, wild silks are worth considerably less than “tame” silks.

CHARACTERISTICS OF SILK:

Silk, a protein fiber like wool, with a smooth hand, is very lustrous and retains its shape well. Silk can take on many different appearances. A raw silk fabric may fool you into thinking that it is cotton or synthetic. The more refined the silk and the smaller the yarn, the more it resembles the look and feel that we know as silky.

Silk is the strongest natural fiber and  is very strong in terms of tensile strength, meaning it can withstand a lot of pulling type pressure without breaking. This should not, however, be confused with wear ability or abrasion resistance. Silk will not stand up to the heavy wear that other fibers will.

Because of it’s good absorbency, fabrics made from silk are comfortable in summer and warm in winter.

Silk creases and wrinkles easily, especially when damp or wet. Some silk clothing manufacturers apply softeners, elastomers, and synthetic resins such as EPSIA – a silicone-containing epoxy crosslinking agent – to increase the dry and wet anti-wrinkling and crease-resistance performance of silk garments. With the family of silicone epoxy crosslinking agents (EPSIA, EPSIB and EPTA) this crease resistance occurs because chemical cross links occur between the silk fibroin strand and the epoxy groups. Research by Zaisheng Cai and Yiping Qiu in the Textile Research Journal (January 2003) reported “in conventional epoxide finishing of silk, organic solvents have to be used, which may be hazardous to the health of the exposed workers as well as the environment.”

Chemical treatments are also added to silk to improve anti-static, water and oil repellency, flame retardant, dimensional stability and other wash-and-wear properties that our easy-care culture seems to expect. Textile chemicals have become an integral and important component of conventional textile and clothing manufacturing. Textile chemicals, also know as textile auxiliaries, have two primary purposes: to increase the efficiency and lower the costs of conventional textile manufacturing; and to create special finishing effects and properties for the clothing.

Silk fabrics have  poor resistance to sunlight and UV exposure and must be protected from the sun. Draperies should be lined and even interlining may be desirable. Colors can fade by oxidation, called “gas fading”, if unaired in storage for a period of time. Impurities in the air may cause as much fading as the direct rays of the sun. Avoid storing silk fabric in a basement or attic near a furnace. Furnaces not only give off fumes but also pull fumes and impurities from other parts of the home.  Silk will become brittle with age and exposure to sunlight.

The silk fibroin from the silkworm is an ideal biomaterial (biocompatibility, biodegradation, non-toxicity, absorption properties, etc.) and has been widely used for sutures and other medical applications.





Wool

9 06 2010

When we talk about wool, we almost always mean the fiber from sheep, although the term “wool” can be applied to the hair of other mammals including cashmere and mohair from goats, vicuna, alpaca and camel from animals in the camel family and angora from rabbits.

As with many discoveries of early man, anthropologists believe the use of wool came out of the challenge to survive – Neolithic man used pelts from animals to keep warm.

Sheep (Ovis aries) were first domesticated 10 000 years ago.  The British sought to protect their own wool industry during the eighteenth century, and passed laws requiring native English wool be used – for example, judges, professors, and students were required to  wear robes made of English wool. Another law required that the dead be buried in native wool. When the American colonies began to compete with the motherland, the English passed a series of laws in an attempt to protect their “golden fleece.” One law even threatened the amputation of the hand of any colonist caught trying to improve the blood line of American sheep.

Today, wool is a global industry, with Australia, Argentina, the United States, and New Zealand serving as the major suppliers of raw wool – but wool is produced worldwide in about 100 countries on half a million farms.   Wool producers range from small farmers to large scale grazing operations.  While the United States is the largest consumer of wool fabric, Australia is the leading supplier. Australian wool accounts for approximately one-fourth of the world’s production.

The annual global output is now estimated at 2.2 billion pounds, yet wool represents less than 5 percent of the world consumption of fibers. Wool is an expensive fiber to produce and process.  Though cotton is the number one plant used for fabrics and the number one natural fiber overall, the number one source for animal fiber is still wool.

Two terms one often sees are Merino and worsted.  The main difference between them is that Merino pertains to the type of fiber while worsted pertains to the process the fibers go through:

Merino is a term used in the textile industry which has varied meanings:  originally it meant wool made from a specific breed of sheep:  the Merino.  Merino sheep are regarded as having some of the finest and softest wool of any sheep: it is finely crimped and soft, fibers are commonly 65 – 100 mm (2.5 – 4 inches) long and generally less than 24 microns in diameter.

But now the term has broader use and may pertain to an article which just contains some percentage of wool from Merino sheep – or even just a fine wool and cotton yarn!  The Australian Wool Testing Authority Ltd is trying to institute a definition for Merino wool, citing fiber diameter and comfort factors.

The essential feature of a worsted yarn is its long, straight fibers which lie parallel to each other, the result of having been both carded AND combed.

So yes, you can have Merino worsted wools!

THE FIBER:

In scientific terms, wool is considered to be a protein called keratin. Its length usually ranges from 1.5 to 15 inches (3.8 to 38 centimeters) depending on the breed of sheep. Fiber diameter ranges from 16 microns in superfine merino wool (similar to cashmere) to more than 40 microns in coarse hairy wools.  Wool has several qualities that distinguish it from hair or fur: it is crimped (meaning it has waves),  it has a different texture or handle, it is  elastic, and it grows in staples (clusters).

Each wool fiber is made up of three essential components: the cuticle, the cortex, and the medulla.

  • The cuticle is the outer layer. It is a protective layer of scales arranged like shingles or fish scales.   They are sometimes described as little “barbs” because it’s the points of the scales that give wool the reputation for being prickly.
    • When two fibers come in contact with each other, these scales tend to cling and stick to each other. It’s this physical clinging and sticking that allows wool fibers to be spun into thread so easily.  And it’s also what causes the fiber to interlock – or felt.   See below for more information on this.

    Scales on a wool fiber under electron microscope

  • The cortex is the inner structure made up of millions of cigar-shaped cortical cells. The arrangement of these cells is responsible for the natural crimp unique to wool fiber.  The amount of crimp corresponds to the fineness of the wool fibers.  A fine wool like Merino may have up to 100 crimps per inch, while the coarser wools may have as few as 1 to 2. Hair, by contrast, has little if any scales and no crimp, and little ability to bind into yarn.  Its wool’s scaling and crimp that make it easier to spin into yarn, because the individual fibers attach to each other, so they stay together.
  • Rarely found in fine wools, the medulla comprises a series of cells (similar to honeycombs) that provide air spaces, giving wool its thermal insulation value.

The Manufacturing Process

The major steps necessary to process wool from the sheep into yarns are:  shearing, cleaning and scouring, grading and sorting, carding.

SHEARING:

Sheep are usually sheared once a year—usually in the springtime. The fleece recovered from a sheep can weigh between 6 and 18 pounds (2.7 and 8.1 kilograms); as much as possible, the fleece is kept in one piece. While most sheep are still sheared by hand, new technologies have been developed that use computers and sensitive, robot-controlled arms to do the clipping.

GRADING AND SORTING:

Grading is the breaking up of the fleece based on overall quality. Wool fibers are judged not only on the basis of their strength but also by their fineness (diameter), length, crimp (waviness) and color.  In wool grading, high quality does not always mean high durability.

In sorting, the wool is broken up into sections of different quality fibers, from different parts of the body. The best quality of wool comes from the shoulders and sides of the sheep and is used for clothing; the lesser quality comes from the lower legs and is used to make rugs.

CLEANING AND SCOURING:

Scouring in the true sense of the word in the textile industry means simply removing any foreign material from the fabric; the term scour grew up around the washing of cottons and linens.

Wool taken directly from the sheep is called “raw” or “greasy”  wool.  It contains a substantial amount of natural contaminants, such as  sand, dirt, grease, and dried sweat (called suint) as well as pesticide residues from the treatment of sheep to prevent disease; the weight of contaminants accounts for about 30 to 70%  of the total weight of the fleece.

To clean the wool, the fiber is washed in a series of alkaline baths containing water, soap, and soda ash or a similar alkali. The scouring effluent contains these impurities, which has high levels of COD (chemical oxygen demand) and BOD (biochemical oxygen demand), suspended solids, organic matter and sheep dip chemicals.  These levels represent a significant pollution load:   the organic effluent from a typical wool-scouring plant is approximately equal to the sewage from a town of 50,000 people.[1]

The effluent is separated into three categories:

  1. grease – when refined, this is known as lanolin, which is saved and sold for a variety of consumer products.
  2. liquor (water) – discharged to sewage works or open waters
  3. sludge – this needs to be disposed of too:   The sludge contains high levels of organic materials such as the potentially toxic sheep dip pesticides (such as organochlorines, organophosphates and synthetic prethroids).   In the EU, landfills will now only accept non-recoverable and inert waste.  Since the global production of wool sludge is over 930,000 tons, research is being done on the feasibility of disposing of scouring waste by composting, incineration and other methods.

The processing stages to this point cause the natural fiber alignment of the scales (or “barbs” as mentioned above) to be completely disrupted; the scales no longer line up “tip to base” as they would in the fleece. Those scales make raw wool itchy and also cause the fiber to shrink when wet.

In order to prevent this shrinkage (also called felting), and to make the wool more comfortable when worn next to the skin, many producers use chlorine to “burn” off the scales…this doesn’t entirely remove them, but it does lessen their profile, and then the fibers are coated with a synthetic polymer resin, which essentially glues down the scales. This allows the wool to be machine washed without felting, and gets rid of the shrinkage of the fabric associated with felting.  This is the chemistry behind Superwash wool.  The tradeoff, of course, is that this chlorination process is highly toxic.

See our blog post on Organic Wool to read about the environmental effects of wool scouring and chlorination.  It’s not pretty.

CARDING:

Next, the fibers are passed through a series of metal teeth.  The teeth untangle the fibers and arrange them into a flat sheet called a web. The web is then formed into narrow ropes known as silvers.   Carding  is one of the processes that untangles the wool fibers and lays them straight; it also removes residual dirt and other matter left in the fibers.  Combing is the next process, which removes shorter length fibers and helps to further straighten the fibers and lay them parallel.  Combing also helps to clean more debris from the fibers.

  • Carding only produces woolenyarn.   Woolen yarns:
    • Have a short staple (1-4 inch long fibers).
    • Are carded ONLY
    • Have a slack twist
    • Are weaker, softer and bulkier than worsted
  • Carding and Combing produces worsted yarn.Worsted yarns:
    • Have a long staple (4 inch and longer)
    • Have a tight twist in spinning
    • Are stronger, finer, smoother and harder than woolen yarns.

CHARACTERISTICS of WOOL:

Wool is highly regarded as one of the most lavish natural fibers in the world.  Lightweight, versatile, resistant to dirt and considered somewhat water repellant, non wrinkling, and durable, wool:

  • Can absorb almost 30% of its own weight in water – and it can also release it.  This makes it breathable and extremely comfortable next to the skin.  It can absorb sweat and release it as vapor, keeping you cool and dry.  It prevents the clammy, cold feeling you may experience when wearing some types of synthetic clothing and sweating.
  • Is resistant to static electricity,  because the moisture retained within the fabric conducts electricity. This is why wool garments are much less likely to spark or cling to the body. The use of wool car seat covers or carpets reduces the risk of a shock when a person touches a grounded object.
  • fabrics have a greater bulk than other textiles because of the crimp, and retain air, which is a great insulation.  It keeps you warm when you’re cold, but insulation also works both ways – Bedouins and Tuaregs use wool clothes to keep the heat out.  And it does not cling to the skin, allowing for air circulation next to the skin.
  • fibers can be bent 20,000 times without breaking (compared to cotton, which breaks after 3,000 bends or rayon, which can be bent only 75 times without breaking), and have the power to elongate (it can be stretched 25 – 30% before breaking), stretch and recover. This natural elasticity and memory  returns to its natural shape
  • doesn’t readily catch fire – its ignition point is higher than cotton and some synthetics.  Even if it does burn, it burns slowly (not melting or dripping as in synthetics) and self-extinguishes when the source of the flame is removed.  It contributes less to toxic gases and smoke than synthetics, and is therefore often specified for high safety environments such as trains and aircraft.
  • has a naturally high UV protection, which is much higher than most synthetics and cotton.
  • is considered by the medical profession to be hypoallergenic.
  • is hydrophilic—it has a strong affinity for water—and therefore is easily dyed.

[1] Christoe, Jock; The treatment of wool scouring effluents in Australia, China and India”,  project # AS1/1997/069; http://aciar.gov.au/system/files/node/9074/AS%2003-04%20AS1-1997-069.pdf





Characteristics of hemp

2 06 2010

We were charmed by this quote, which was written by Yitzac Goldstein of Earth Protex, many years ago:

Before Huang-Ti’s time                                      
clothing was made from skins of birds and animals.

But as time went on

people increased and animals were few

Causing great hardship.

So Huang-Ti ordained that

Clothing should be made from hemp fiber.

This is how the spiritual leader  changed matters

For the people’s benefit.

6th century A.D. historian Khung Ying-Ta on

The Yellow Emperor, Huang-Ti, 27th century B.C.

I love hemp, maybe just because of the lore associated with the plant – and I don’t mean the lore surrounding the hallucinogenic properties of the plants that are bred for high THC content!  So let’s get that part out of the way fast:

Hemp is another word for the plant Cannabis sativa. Yes, marijuana comes from this same plant genus – and so does hops, used to produce beer for millennia. But what we call “industrial hemp” is a different variety (or subspecies), called Cannabis sativa sativa.  Marijuana is from Cannabis sativa indica, which is bred to contain between 5 – 10% of the intoxicating substance delta-9 tetrahydrocannabinol, or THC.  Industrial hemp, Cannabis sativa sativa, contains less than one tenth that amount.  Industrial grade hemp is not marijuana – it doesn’t look the same and if you tried to smoke it you’d probably die of carbon monoxide poisoning before you felt anything but sick. For more about the differences between the two varieties click here or go to the Industrial Hemp website.

Hemp is unique among other crops in that every part of the plant has utility and potential market value.  Here are some interesting facts about hemp that contribute to the lore I’m referring to:

  • In 1941 Henry Ford built a car with a plastic made from hemp and wheat straw.
  • Both George Washington and Thomas Jefferson grew hemp on their plantations; in fact the colonial government mandated that people grow hemp.  Settlers used hemp fiber as money and to pay taxes.
  • The original Levi Strauss jeans were made from hemp.
  • The July 4, 1776 Declaration of Independence  was written on hemp paper.

The plant has been used for millennia for food, fibers and fuel.   Today it is said that over 30,000 different products can be made from hemp.  Hemp’s oilseed makes high-grade food and beauty products.  The stalks produce fiber and cellulose.  And today, because of its length and strength, hemp fiber is woven into natural advanced composites, which can then be fashioned into anything from fast food containers to skateboard decks to the body of a stealth fighter.  There are over two million cars on the road today with hemp composite components.

But hemp for luxurious fabrics?  I remember those macramé plant hangers that were all the rage in the 1970’s.  Hemp has a public relations campaign to wage, because when I thought of hemp a few years ago (before my enlightenment) all I could imagine was burlap bag and sisal rugs.  Turns out the technical revolution has even found hemp:  new developments from the 1980’s  in retting and processing the stalks has meant that the hemp fibers produced today are soft and lustrous enough for even the finest fabrics.

Many end users look for comfort and durability in choosing a fabric, so hemp’s softness and high abrasion resistance make it a competitive choice.  Hemp fiber’s positive qualities have been recognized over thousands of years of real life applications.  The texture of pure hemp textiles resembles that of flax linen, appealing to the eye with its subtle variations in thickness, but it is also versatile and can be blended with other fibers to create many different looks.  Hemp’s versatility as a textile is stunning:  hemp fibers can be woven alone or with other fibers to produce weaves from rugged canvas to the lightest, silkiest  gauze,  in an unlimited array of colors and finishes.  Hemp has a beautiful natural luster and a lush hand and drape not found with any other natural or synthetic fiber, even linen.

Hemp’s characteristics as a textile make it a desirable choice in many applications:

  • Hemp is stronger and more durable than any other natural fabric, including linen, which almost matches hemps abrasion resistance and tensile strength.  The result is that hemp has a longer lifespan than other natural fabrics.[1] (Patagonia is just one of the many companies which has published studies which demonstrate hemp’s superior strength; results for these studies range from 3 to 8 times stronger.)  Products made from hemp will outlast their competitors by many years.
  • Not only is hemp strong, but it also holds its shape, stretching less than any other natural fiber. This prevents hemp fabric used in upholstery, demountable panels, acoustic paneling or as wallcovering from stretching out or becoming distorted with use.
  • Hemp fabric withstands, even benefits from, commercial laundering. Its inherent luster and light reflective qualities are enhanced by washing; it becomes finer and more luxurious with use. Hemp also possesses excellent soil-release properties because it sheds a microscopic layer each time it is laundered. This eliminates soiling and exposes a fresh surface. In effect, this means that hemp retains its sleek sheen every time it is washed, that it never dulls, and that it releases stains more easily than other fabrics.
  • Hemp may be known for its durability, but its comfort and style are second to none.  The more hemp is used, the softer it gets: it wears in, not out, thriving on regular use and machine washing without suffering fabric degradation. Hemp actually becomes softer, more resilient and more lustrous as a result of washing.
  • Hemp’s superior absorbency, due to its porous nature, means that it is very breathable and quick drying. Hemp can absorb up to 20% its own weight while still feeling dry to the touch (vs. polyester, which can absorb a maximum of 6%). This is important in the case of any fabric that is in contact with human skin, such as sheets, as perspiration is rapidly absorbed. It feels cooler in summer yet during cool weather, air which is trapped in the fibers is warmed by the body, making it naturally warm.
  • Hemp’s absorbency allows it to accept dyes readily and retain color better than other natural fibers, including cotton.
  • Hemp has a high resistance to ultraviolet light; it will not fade or disintegrate from sunlight as quickly as other natural fibers. (Tilly Endurables introduced a new hat in 2004 after testing its hemp fabric to a UPF of 50+, the maximum ultraviolet protection rating given.[2]) UV damage is especially a problem for draperies and marine interiors, so hemp would be a good natural fiber choice for these applications.
  • Hemp fiber is highly resistant to rotting, and its resistance to mildew, mold and salt water led to its premier use in marine fittings:  the majority of all twine, rope, ship’s sails, rigging and nets up to the late 19th century were made from hemp.  The word canvas itself is derived from cannabis.
  • Finally, any product made of hemp is fully biodegradable and easily recyclable.

Hemp as a crop is also a standout.  The bio-regional model of agriculture focuses on obtaining high value for the resources of the local land, recycling the waste and end products ad infinitum and thereby creating a “closed circle” of farming and industry.  Hemp is an elegant solution to the crises created by modern agribusiness and conventional cotton production because:

  • Hemp grows well without the use of chemicals:  usually no pesticides or fungicides are used because it has few serious fungus or pest problems – although the degree of immunity to attacking organisms has been greatly exaggerated.  Several insects and fungi specialize exclusively in hemp!  But despite this, the use of pesticides and fungicides are usually unnecessary to get a good yield.    No herbicides are generally used because dense plantings shade out weeds; no defoliants are needed (as they are with machine harvested cotton) because the dried foliage is not a problem for harvesting.
  • Hemp requires less water to thrive than cotton – is actually drought tolerant –  and usually grows well without irrigation.  Globally, 77% of cotton crops are irrigated.
  • Hemp has a fiber yield higher than any other agricultural crop, thereby requiring less land for equal yield:

Average fiber production, in pounds, per acre:

Conventional cotton Organic cotton Flax Wool Hemp
121 – 445 lbs. 80  –  102 lbs. 323 – 465 lbs. 62  lbs. 485 – 809 lbs.

Source: UK-government funded project at University of London, “Demi: design for sustainability” (www.demi.org.uk), © Kate Fletcher, 1999

This yield translates into high biomass, which can be converted into fuel in the form of clean-burning alcohol, or no-sulphur man-made coal.

The most widespread claim for the environmental friendliness of hemp is that it has the potential to save trees that otherwise would be harvested for the production of pulp.  If  hemp reduces the need to harvest trees for building materials or other products, its use as a wood substitute will tend to contribute to preserving biodiversity.  Hemp may also enhance forestry management by responding to short-term fiber demand while trees reach their ideal maturation. In developing countries where fuel wood is becoming increasingly scarce and food security is a concern, the introduction of a dual-purpose crop such as hemp to meet food, shelter, and fuel needs may contribute significantly to preserving biodiversity.

For more on hemp, here are some resources to get you started:

Organizations

Web

Journals

  • Journal of the International Hemp Association. Vol. 1 (1994)–Vol. 6 (1999). (Vols. 1–5 and part of Vol. 6 available online at mojo.calyx.net/~olsen/HEMP/IHA/). Superseded by Journal of Industrial Hemp.
  • Journal of Cannabis Therapeutics. Hawarth Press. Vol. 1 published 2001.
  • Journal of Industrial Hemp. Haworth Press. Vol. 1 to be published 2002.

[1] Kerr, Nancy, PhD, “Fabulous Fibers? Can hemp compete with natural and manufactured fibers?” AgFibe2002 conference, Winnipeg, MB, Nov. 13 – 15, 2002.

[2] Press release, Tilly Endurables 2004; also see http://www.backpackgeartest.org/News/article.php?story=20050210193045692.