Should I choose a hemp or linen fabric?

5 08 2015

We are often asked for 100% hemp fabric in lieu of linen fabrics. We offer hemp and adore it, but it may not be the best eco choice.  Make no mistake – we love hemp, we sell hemp fabrics and we think the re-introduction of hemp as a crop would be a boon for American farmers and consumers.

But hemp that is used to produce hemp fabric via conventional methods – as opposed to GOTS methods – is an inferior choice to any GOTS certified fabric. So the overriding difference is not between hemp and any other fiber, but between a GOTS certified fabric versus one that is not GOTS certified, because GOTS certification assures us that the fabric is free of any chemicals that can change your DNA, give you cancer or another dread disease or affect you in other ways ranging from subtle to profound. It also assures us that the mill which produced the fabric has water treatment in place, so these chemicals don’t pollute our groundwater – and that the mill pays fair wages to their workers who toil in safe conditions!

The GOTS certification requires that the fiber used in the fabric be third party certified organic. Organic linen is more available and less expensive then organic hemp, so we often use linen instead of hemp in our fabrics. Using organic linen instead of organic hemp keeps the price lower for you and you do not give up any performance characteristics at all.   Allow me to say that once more: You do not give up any performance at all.

To begin with, do not be confused by the difference between the fiber and the cloth woven from that fiber – because the spinning of the yarn and the weaving of the cloth introduces many variables that have nothing to do with the fibers. Both hemp and flax (from which linen is derived) are made from fibers found in the stems of plants, and both are very laborious to produce. The strength and quality of both fibers are highly dependent on seed variety, the conditions during growth, time of harvest and manner of retting and other post-harvest handling.

Yarns, made from the fibers, are graded from ‘A’, the best quality, to below ‘D’ and the number of twists per unit length is often (but not always) an indication of a stronger yarn.   In addition, the yarns can be single or plied – a plied yarn is combined with more than one strand of yarn. Next, the cloth can be woven from grade ‘A’ yarns with double twist per unit length and double ply into a fabric where the yarns are tightly woven together from cloth that is lightweight or heavier, producing a superior fabric.  Or not.

Now let’s look at some of the differences between hemp and linen:

Hemp and linen fibers are basically interchangeable – there is very little to distinguish flax fibers from hemp fibers.  In fact,  hemp’s fibers so closely resemble flax that a high-power microscope is needed to tell the difference. Without microscopic or chemical examination, the fibers can only be distinguished by the direction in which they twist upon wetting: hemp will rotate counterclockwise; flax, clockwise.  And in general, they tend to have the same properties.

In general, there are many similarities between cloth made from hemp and cloth made from linen:

  • Both linen and hemp become soft and supple through handling, gaining elegance and creating a fluid drape.
  • Both hemp and linen are strong fibers – though most sources say hemp is stronger (by up to 8 times) than linen (even though the real winner is spider silk), but this point becomes moot due to the variables involved in spinning the fiber into yarn and then weaving into fabric.   The lifespan of hemp is the longest of all the natural fibers.
  • Both hemp and linen wrinkle easily.
  • Both hemp and linen absorb moisture. Hemp’s moisture retention is a bit more (12%) than linen’s (10 – 12%)
  • Both hemp and linen breathe.
  • Both hemp and linen are natural insulators: both have hollow fibers which means they’re cool in summer and warm in winter.
  • Both hemp and linen have anti-bacterial properties.
  • Both hemp and linen benefit from washing, becoming softer and more lustrous with each wash.
  • Both hemp and linen are resistant to moths and other insects.
  • Both hemp and linen absorb dyestuffs readily.
  • Both hemp and linen biodegrade.

In general, hemp fiber bundles are longer than those of flax.   So the first point of differentiation is this: the length of the fibers. Hemp fibers vary from 4 to about 7 feet in length, while linen is general 1.5 to 3 feet in length. Other differences:

  • The color of flax fibers is described as yellowish-buff to gray, and hemp as yellowish-gray to dark brown.
  • Hemp is highly resistant to rotting, mildew, mold and salt water.
  • Hemp is also highly resistant to ultraviolet light, so it won’t fade or disintegrate in sunlight.
  • Hemp’s elastic recovery is very poor and less than linen; it stretches less than any other natural fiber.

The biggest difference between hemp and linen might be in the agricultural arena: Hemp grows well without the use of chemicals because it has few serious 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. Hemp has a fiber yield that averages between 485 – 809 lbs., compared to flax, which averages just 323 – 465 lbs. on the same amount of land.  This yield translates into a high biomass, which can be converted into fuel in the form of clean-burning alcohol.

Farmers claim that hemp is a great rotation crop – it was sometimes grown the year prior to a flax crop because it left the land free of weeds and in good condition.   Hemp, it was said, is good for the soil, aerating and building topsoil. Hemp’s long taproot descends for three feet or more, and these roots anchor and protect the soil from runoff. Moreover, hemp does not exhaust the soil. Additionally, hemp can be grown for many seasons successively without impacting the soil negatively. In fact, this is done sometimes to improve soil tilth and clean the land of weeds.

The price of hemp in the market is far higher than for linen, despite hemp’s yields.   We have no idea why this is so.

The overriding difference is not between hemp and linen, but between a hemp OR linen fabric that has a GOTS certification and one that does not. That means that a conventional hemp fabric, which enjoys all the benefits of hemp’s attributes, also introduces unwanted chemicals into your life: such as formaldehyde, phthalates, heavy metals, endocrine disruptors and perhaps soil or fire retardants.   The GOTS certified fabric is the better choice. If the choice is between a conventional hemp fabric and a GOTS certified linen fabric, we wouldn’t hesitate a second to choose the linen over the hemp, especially because hemp and linen are such close cousins.

 

 

 

 

 

 

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What does “mercerized” cotton mean?

5 12 2012

fullsizeMercerization is a process applied to cellulosic  fibers  – typically cotton (or cotton-covered thread with a polyester core)  but hemp and linen can be mercerized also – to increase luster.  It is done after weaving (in the case of fabrics) or spinning (for yarns or threads).  But early on it was found that the process also had secondary benefits:  the mercerized fibers were able to absorb more water, and therefore absorb more dye, making the color of the dyed cloth brighter and deeper.  The difference is dramatic:  mercerization increases the absorption of dyestuffs by as much as 25%.[1]  unmercerized-101mercerized-101Not only is the color brighter, it also gives the cloth a better resistance to multiple washings,  keeping the colors bright and unchanged over time.   In addition to increasing luster and affinity to dyestuffs, the  treatment increases strength, smoothness, resistance to mildew, and also reduces lint.  So higher quality yarns and fabrics,  for example, are always mercerized.

The process goes back to the 1880’s.   John Mercer was granted a British Patent for his discovery that cotton and other fibers changed character when subjected to caustic soda (NaOh, also known as sodium hydroxide or lye), sulfuric acid, and/or other chemicals.   One of the changes was that caustic soda caused the fiber to swell, become round and straighten out.  But so what – these changes didn’t impart any luster to the fibers, so his patent was largely ignored.  Then in 1890 Horace Lowe found that by applying Mercer’s caustic soda process to cotton yarn or fabric under tension, the fabric gained a  high luster  as a result of the light reflection off the smooth, round surface created by the NaOH. It became an overnight success and revolutionized the cotton industry. The rest is history.[2]

Later testing proved that cotton fiber in its roving state (no twist in the yarns) would absorb more NaOH than fiber in a twisted state and as a result would absorb more water or dye.  Since fine, long stapled fiber gives the best absorption with the lowest twist, ( some twist is required for treating under tension to gain luster) it is usually the long fiber types of cotton (Sea Island, Egyptian, Pima) that are selected for yarn to be mercerized.   So mercerized cotton fabric starts with a better quality cotton fiber.

How is it done?

To get the desired luster and tensile strength,  cotton is held under specified tension for about ten minutes with an application of between 21%-23% caustic soda (NaOH) and wetting agents (used to facilitate the transfer of the NaOH into the fibers), at room temperature.  Then the fabric is neutralized in an acid bath.

Luster is a result of light reflection off a surface. The more glass like the surface, the better the luster. Yarn in its spun, treated state still has a very fine covering of tiny fiber ends (fuzz). This fuzz is removed by passing the yarn (or fabric) through a controlled heated atmosphere termed singeing (gas fired in the past, electric more currently) resulting in a cleaner surface.  (Luster is a result of light reflection off a surface. The more glass like the surface, the better the luster.)
You knew I’d have to look at the toxicity profile of sodium hydroxide, which is considered one of the building blocks of chemistry.  It’s a very powerful alkali.   It’s used in industry in a broad range of categories: chemical manufacturing; pulp and paper manufacturing; cleaning products such as drains, pipe lines and oven cleaners ; petroleum and natural gas; cellulose film;  and water treatment as well as textiles. The US Food and Drug Administration (FDA) considers sodium hydroxide to be generally safe, and recognizes it as not being found to pose unacceptable dietary risks, though it is generally only used on food contact surfaces rather than in foodstuffs.

The chemical is toxic to wildlife, and the EPA requires that effluent containing NaOH not be discharged into groundwater.  Because sodium hydroxide falls in the group of chemicals (salts) which are by far the most often used in textile processing, the sheer volume of NaOH used by the textile industry is important to recognize.  Usual salt concentrations in cotton mill wastewater can be 2,000 – 3,000 ppm[3], far in excess of Federal guidelines for in-stream salt concentrations of 230 ppm.  So treatment of effluent is very important, as prevention is the only reasonable alternative to solve the environmental problems associated with this hard-to-treat, high volume waste.  I have read that electrochemical cell treatment might be a substitute for using NaOH to mercerize.  This process occurs in a low voltage electrochemical cell that mercerizes, sours, and optionally bleaches without effluents and without the purchase of bulk caustic, neutralizing acids, or bleaches.





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.