behind the scenes...
Natural vs. Synthetic Fibers
The number of synthetic fibers being used to produce yarns and clothing has grown significantly in recent years. While the primary synthetics used in yarn are acrylic, polyester, polyamide and nylon, any of the following may be found in yarn as well; elastic, microfiber, modacrylic, modal, payette, rayon, sinflex, soysilk, spandex or tencel. If you want to stick to natural, you'll want to watch out for all these fibers, as well as yarns labelled shimmer, sparkle, glitter, metallic or shine.
The variety of natural yarns available to knitters has grown to include quite a dazzling assortment. There are yarns available to suite every need, from soft lacy cashmeres and silks, to thick roving wools. The following are the most prominent of the natural fibers available in yarns today; alpaca, angora, bamboo, bison, camel, cashmere, cotton, hemp, linen, llama, merino wool, mink, mohair, possum, qiviut, silk, wool and yak.
When considering synthetic fibers, it's important to keep in mind that polyfill stuffing is made of the same synthetic fiber as polyester yarn. There are a number of natural stuffing options available including cotton, wool, buckwheat, shredded natural rubber and kapok. Consider saving your yarn clippings and scraps to use for stuff small toys.
The same applies to synthetic fabrics and embellishments, which can be easily substituted with natural alternatives.
There's been a lot of talk about synthetic yarns versus natural yarns. But what are the specific differences? Are you looking for reasons to switch to natural, or trying to stick to synthetic? Well let's take a look at some comparative facts and you can decide for yourself:
So just what do synthetic fibers have going for them? In the end, the biggest draw is price. In a day when money is tight for many, price vs. quality is not an easy choice. But the way we see it, it's better to pay a little more money than to pay the price which inevitably results from the hazards of synthetics. The more research comes out, the more we're left to wonder just how big of a price we're going to pay one day flooding the world with synthetic fibers.
For those who want to learn more about the specific natural fibers and their advantages, we recommend The Fleece & Fiber Sourcebook, a priceless guide to the natural fiber industry. Plus it's chalk full of cute critter pictures!
The Natural Fiber Process
Suri Alpaca with young in Peru
Natural fibers include alpaca, angora, bamboo*, bison, cashmere, camel, cotton, guanaco, hemp, linen, llama, mink, mohair, possum, qiviut, silk, vicuña, wool, yak as well as other less common fibers. Alpaca, cotton and wool are the most commonly used in yarns. The process of making natural yarns begins with the animals and plants from which each fiber is derived. The exact methods vary depending on the fiber and farm. We will review the processes used to make wool and cotton yarns. Though the exact techniques may vary slightly, the basic processes apply to the other fibers as well.
Cotton field in Texas
WOOL - From Sheep to Spun Yarn:
There are 6 steps involved in making wool yarns; shearing, skirting, washing, carding, spinning and dyeing. Shearing can be done one of two ways; either with hand shears, or using power shears. Professional shearers can shear an entire sheep in less than one minute, without even scratching the sheep. When shearing, the fleece is usually removed in a single piece. Once the fleece has been removed from the sheep, the next step is to skirt and card it.
Skirting is the process of removing unusable or extremely soiled bits of wool from the fleece, before processing. With animals such as sheep, the fleeces contain a lot of lanolin, which is either removed or left in the fleece, depending on how the fleece is to be used. If the finished yarn is meant to be water-repellent, then the lanolin will not be removed. Once the fleece has been skirted, it is carefully washed to remove extraneous vegetable matter, twigs, straw, etc. and lanolin if its to be removed. The washing process may be done with large washing machines or by hand and can be very time consuming. Much care has to be taken when washing fleeces, because too much agitation can result in undesired felting.
After the fleeces have been cleaned and dried, they may be spun immediately, but they are usually carded first. Carding is the process of combing the fibers into fine straight layers, so that they can be easily spun. Once the fibers have been spun, they are referred to as either a rolag (if handcarded) or roving (if machine carded).
At this point, the fibers are prepared for spinning. They may be handspun using a spindle or spinning wheel or machine spun. After spinning, the yarn will be dyed and rolled for packaging. The wool fiber may also be sold for spinners after cleaning and carding or as roving, both for spinning and for big-needle knitting and thrumming.
COTTON - From Boll to Ball:
Because cotton is a plant fiber, the process used is slightly different than for animal fibers.
Cotton is a soft, fluffy fiber, which grows in a boll (a protective shell around the fiber) around the seeds of cotton plants. Cotton is grown world wide, especially in tropical and subtropical regions, such as Mexico, Australia and Africa. It has been used for thousands of years and is separated into several categories. Egyptian Cotton is generally considered one of the best, however few 'Egyptian Cottons' are truly from Egypt.
A sheep shearer uses a supporting back sling while shearing sheep
Cotton bolls
After harvesting, the cotton fiber, which is attached to the seeds is placed in a cotton gin. The gin separates the seeds and other residue (grass, leaves, dirt, etc.) from the fiber.
There are several types of gins. Saw Gins are circular and grab the fiber, pulling it through a narrow grating, too small for the seeds to pass through. Roller Gins, which are used for longer staple cottons, run the cotton over a leather roller attached to a blade, which detaches the seeds.
Once the cotton has been ginned, it is referred to as lint and is compressed into bales, which are then sent off to be carded, spun and dyed.
A woman spins yarn in Nepal
An antique cotton gin on display
Armenian women harvest cotton
*Bamboo yarns, by the strictest definition, are not natural since the bamboo is chemically processed in order to turn it into yarn. The process is actually similar to the process of making soap, where strong solutions of sodium hydroxide are used to change fat into soap. The other chemical used is carbon disulfide, an organic solvent that evaporates very quickly. In large concentrations it is a toxin. However, because it evaporates so quickly, it does not remain in the fibers. It also breaks down once released, in a few days, to simpler carbon and sulfur compounds which are all around us in daily life. The end product is very clean, non-toxic and actually very eco-friendly and biodegradable. Unlike synthetic yarns or fabrics, bamboo fibers will decompose in soil in a short time.
The Synthetic Fiber Process
Synthetic fibers have been made over the years by scientists, in an effort to create fibers superior to those found in nature. The first official synthetic fiber was Nylon, originally designed as a replacement for silk for use by the U.S. Military. Since then, a huge array of synthetic fibers have flooded the market, most commonly including polyester, acrylic, elastic and spandex. Other, less commonly recognized synthetic textile fibers include microfiber, modacrylic, modal, polyamide, rayon, sinflex, soysilk, tencel and others.
Joseph Swan, creator of the first synthetic fiber
Wallace Carothers, the first to synthesize nylon
However, in spite of their attempts, the rise of the synthetic fiber industry has not created fibers which excelled their natural counterparts, but rather has created an array of cheap, non-degradable fiber.
Though synthetic fibers may sometimes be capable of handling rough machine washing or be longer lasting than natural fibers, their overall impact is negative on both human health and the environment.
Unlike natural fibers whose production process is clean and simple, synthetic fibers are a result of, well, synthetic processing. In most cases the synthetic materials are pushed through tiny holes, called spinnerets, into the air, forming a super-thin thread. This process is usually referred to as extruding. Once these threads have been made, they are spun, dyed and packed in much the same way as natural yarns. Although certain adjustments have to be made to the process, since synthetic fibers often react differently to spinning and dyeing than natural fibers.
So far, synthetic fibers may not sound too bad. However, the true secret to synthetic fibers lies not in the extruding or post-extruding process, but in what comes before that........
The chemical structure of the Polyacrylonitrile repeat unit
ACRYLIC - From Polyacrylonitrile to Acrylic Fiber
Acrylic fiber is created from a polymer [a synthetic compound consisting of large molecules made up of a linked series of repeated simple monomers (a molecule that may bind chemically or supramolecularly to other molecules)] called Polyacrylonitrile, also known as Creslan 61. The polymer is formed by what's called free-radical polymerization. The polymer is then dissolved in a solvent such as N-dimethylformamide (DMF) which is suspected to cause birth defects. The concern about DMF is significant enough that, in some places, women are banned from working with it.
It is then sent through a multi-hole spinneret and the resulting filaments are coagulated in a water-based solution of DMF. This part of the process is called wet spinning. The resulting fibers are then washed, stretched and crimped . The fiber is then spun and dyed into yarn, thread or may go on to be used in the production of carbon fiber, boat covers, upholstery, etc.
The majority of acrylic fibers are made in the Middle East, India, Mexico and South America. Americanacrylic brands include (or at one time included) Acrlian, Creslan, Dralon and Drytex.
Ball-and-stick model of a
dimethylformamide molecule
POLYESTER - From Poly-mer to Poly-ester
Polyester is made primarily from a synthetic polymer called Purified Terephthalic Acid (or PTA). Though that may sound innocent, PTA is also used in the production of water bottles, capacitors, insulating tape, smoke grenades, etc. A catalyst called Antimony Trioxide, which is suspected to have carcinogenic potential in humans, is added to the PTA.
Then Titanium dioxide is added to dull the color. Other chemicals are then added to allow the fibers to pass through the machinery smoothly.
At this point, it is run through the spinnerets then into cool, dry air. The filaments that emerge from each hole in the spinneret are collected to form small ribbons which are then bathed in spin finish and then coiled in cans. At this point in the process, it is called undrawn TOW.
Ball-and-stick model of a PTA molecule
The filaments are then run through the draw machine which takes undrawn TOW's from multiple cans and runs them through a hot water trough to raise the polymer temperature. The polymer is then drawn (pulled) 4 times through a steam chamber or a hot water trough. Once the drawing is complete, the filaments are passed through heated cylinders to shrink and strengthen them. The fiber is then passed through a hot water bath and a steam chest to heat it up again. More spin finish is applied and the fiber is run through a drying machine.
The fibers are then cut to the desired length and sent to the spinning mills to be spun, dyed and rolled.
The deeper you dig, the more obvious it becomes that synthetic fibers are truly deserving of their name. They're created from toxic materials, bathed in toxins, heated, stretched, bathed again, on and on until the fiber is workable. Then spun into pretty yarns to be used for new-born baby blankets, adults and kids clothing, toys, etc.
Though each synthetic fiber is slightly different and the process involved in the production of each varies slightly, they all have one thing in common; when all things have been considered, none of them are truly superior to natural fibers.
All images on this page courtesy of WikiMedia Commons