Flax, Linum usitatissimum. The Flax fibers, seeds, and flower.

How Linen is Made

Technically, linen is a vegetable. Linen fabric is made from the cellulose fibers that grow inside of the stalks of the flax plant, or Linum usitatissimum, one of the oldest cultivated plants in human history.

Flax is an annual plant, which means it only lives for one growing season. From seed-planting, it is ready to be harvested in about a hundred days. Unless the weather is particularly warm and dry, flax requires little watering or attention during this time. It grows to about three or four feet tall, with glossy bluish-green leaves and pale blue flowers, though on rare occasions, the flowers bloom red.

Flax is cultivated around the world not only for its fine, strong fibers, but also for its seeds, which are rich in nutrients such as dietary fiber and omega-3 fatty acids. Flax oil is also a popular drying oil amongst oil painters.

Types of Flax

To date, no method of flax cultivation has been discovered that maximizes both quality and yield of both seed and fibers. To obtain the highest quality flax fibers, one must harvest before the plant fully matures, which results in poorer-quality oil. Conversely, if harvest is undertaken after maturation to obtain the best oil, the fiber quality deteriorates. Thus,  two distinct types of flax plants are cultivated:

  • The linseed variety is grown primarily to extract the seed’s highly nutritious oil. This type is fairly short and produces many secondary branches, which increases seed yield.

  • The flax variety tends to grow taller, more slender, and with less branches. It is cultivated in order to extract the very long fibers  from inside the wooden stem of the plant,  which are then spun and woven into linen fabric. The taller the flax plant, the longer the fiber.

Flax Growing Environments

Flax can grow in a variety of climates, but it flourishes in cool, damp environments. It cannot tolerate extreme heat, so the planting schedule of flax varies from country to country depending upon regional climatic conditions. For instance, in warmer regions flax is sown in the winter so that harvesting can be undertaken before the heat of early spring. Because it requires a lot of organic components, flax grows best in deep loams and alluvial soils such as the Nile River valley.

Flax Harvest

Flax is ready to be harvested for its fibers when the stem begins to turn yellow and the seeds turn brown. On some farms however, the plant is harvested prior to seed germination. This yields exceptionally fine fibers, but leaves the grower without any seeds for the next planting and subsequently dependent upon foreign imports.

Harvested flax bundlesThe stems of the flax plant are preferably pulled up with the root system somewhat intact, rather than cut at the base. This maximizes the quality of the fiber in several ways.  First, the valuable fibers run the length of the stalk all the way into the roots, so pulling up the plant by the root increases the length of the fiber produced. This practice also prevents the plant sap from leaking out of the cut stalk, a process which dries out the fibers and ultimately results in poorer-quality fabric.

Although the agricultural industry has made great strides in mechanized farming, machine harvesting of flax is still unable to preserve the root system during harvest. For this reason, despite the extremely laborious process of manual harvesting, the highest quality linens are still made from flax plants that were pulled out of the earth by hand. Fabric made from hand-harvested flax is finer, more supple, and more highly prized than fabric made from flax that is machine-harvested.

Traditional Flax Processing. From Fibers and Seeds to Linen.

After harvest, flax stalks are allowed to dry in open air for several weeks before they undergo threshing, or removal of seeds from the stalk by crushing open the dried seed pods. Hand threshing is usually achieved by simply beating the dried stalks until all the seed pods have been crushed, then shaking the seeds free.

Flax fibers are considered bast fibers. Bast fibers are fibers collected from the phloem, or the inner-bark of the plant. Fabrics made from these fibers are typically quite strong and  durable fabrics. Aside from linen, a few other fabrics made from bast fibers include hemp, ramie, and rattan.

What's in a Flax Fiber?

You may remember from your Biology 101 class that the phloem is one of the two vascular structures inside of plants that carry nutrients throughout the organism (the other is the xylem, or the woody core). Bast fibers are long, narrow supportive cells inside the phloem that provide it with great tensile strength, but still allow flexibility of the plant stem due to the fibers’ characteristic fiber nodes, or weak points that are distributed randomly along the length of the fiber. These fiber nodes are also what make linen fabric flexible without being brittle.

Separating Out the Flax Fiber 

The xylem and phloem of plants are bundled together by calcium ions and a sticky protein called pectin, which must be broken down in order to separate the valuable bast fibers from the plant’s vasculature so that they can be processed and spun into yarn. This is achieved via a process called retting--or, literally, rotting. And yes, with the same awful smell!

Retting (a quick biology lesson from DeckTowel). Let's get technical. 

Cross section of a bast fiber. X=xylem, P=phloem, C=cortex, BF=bast fibersThe malodorous process of retting can be achieved in a variety of ways, but it typically involves prolonged exposure of the stalk to moisture. Plants hold themselves upright by increasing water uptake into their cells, which causes the plasma membrane to swell and increases internal pressure against the cell wall. This pressure keeps the plant structures stiff (Biology 101 review: Turgor pressure). Prolonged water exposure during retting eventually causes the cells of the phloem to lyse, or burst open, and allows local micro-organisms that break down the sticky pectins to invade the plant cell.

The image to the right is a cross section of a bast fiber: "X" is xylem; "P" is phloem; "C" is cortex; "BF" is bast fibers.

How do these micro-organisms break down those sticky pectins? A man named Sergei Winogradsky figured out the answer to this question back in the 1890s. Winogradsky, a microbiologist and soil ecologist, is actually quite famous for this answer - his discovery of chemosynthesis - a process wherein autotrophs (organisms that make their own food) absorb carbon and inorganic nutrients from their surrounding environments in order to mediate the chemical reactions with which they create their own energy.

Prior to this discovery, scientists believed that all autotrophs were dependent upon sunlight for energy production (remember photosynthesis?). But Winogradsky found a little bacterium living in the root nodules of legume plants that changed everything. He identified it as Clostridium Pasteuranium, an obligate anaerobe that, by definition, cannot survive in the presence of atmospheric oxygen (O2). The presence of this autotrophic bacterium inside of the root nodules, without access to atmospheric oxygen and therefore also without access to sunlight, led Winogradsky to investigate how it managed to survive.

He found that C. Pasteuranium uses water molecules to break up the sticky pectin bonds that hold the bast fibers to the phloem, a process called hydrolysis.  It then uses the chemical pieces of the broken up pectins to create ammonia (NH3) out of free, bioavailable nitrogen (N2) in its surrounding environment, which can then be utilized by the bacteria in its metabolic processes. This is is called nitrogen fixation. You’ve learned about it before this biology lesson (the nitrogen cycle), and you’ve seen it with your own eyes (lightning).

Scientists have since isolated more than 22 different kinds of autotrophic, pectin-dissolving bacteria from retted flax, mostly belonging to the Clostridium family.

Methods of retting

  • Flax bundles retting in the River Lys, BelgiumWater retting is the most widely-employed practice and produces the highest quality fibers. It is best accomplished in stagnant or slowly-moving waters, like ponds, bogs and streams. As a rule, the more stagnant the water source, the more abundant the bacterial fauna and the faster the retting process. Flax bundles weighted down in ponds and bogs generally ret in anywhere from a few days to a couple of weeks, depending on water temperature. Because the water is stagnant and the microfauna abounds, pond or bog retting is particularly foul-smelling. Stream retting usually takes a few weeks longer, but yields cleaner (and less stinky) fibers.

  • Dew retting is the preferred method in areas where water sources are limited but that enjoy warm daytime temperatures and heavy nighttime dews. Flax stalks are spread out evenly across a grassy field, where the combination of air, sun and dew causes fermentation, which dissolves much of the stem within  2-3 weeks. Dew-retted fibers are typically of poorer quality and more darkly pigmented than natural water-retted fibers.

  • Tank retting takes place in large vats that are typically made of cement, as the acidic waste products of the bacteria corrodes metal. Stalks are first leached, or soaked, for 4-8 hours to remove dirt and pigment from the bundles. This water is then changed, and the bundles allowed to soak for 4-6 more days to complete the retting process.

  • Flax can also be retted chemically, which speeds up the process. It is, however,  more harmful to both the environment and the fibers themselves, and is therefore not preferred.

Dressing the flax

The retted stalks, called straw, are dried mechanically or in natural air, and are then usually stored for anywhere from a few weeks to months in order to allow curing to take place. After curing, the woody stalks that still cling to the bast fibers are further broken, usually by passing the brittle straw through rollers that crush the wood into smaller pieces that can be more easily removed, a process called scutching.

Scutching flax fibersScutching involves scraping a small wooden knife down the length of the fibers as they hang vertically, pulling the broken woody bits away from the fiber. This is a labor-intensive process. One person scutching can produce only about 15 pounds of flax fibers per day; less if the fibers are coarse, hard, or have been poorly retted. The small pieces of leftover bark that remain after scutching are called shive, and are sometimes used as a filler in thermoplastic composites.

The separated bast fibers are next heckled, or combed through a bed of nails that splits and polishes the fibers, and removes the shorter tow fibers from the mix. These tow fibers can then be spun into a coarse yarn from which low-quality linen products are made.

The longer fibers (sometimes as long as three feet!) are then ready for spinning.

Spinning

The (at long last) separated flax fibers, called stricks, are traditionally spun by hand using a distaff. A distaff is simply a long vertical pole that attaches to a spinning wheel from which the fibers are hung. This helps keep the fibers organized and prevents them from turning into a tangled mess. Spinning involves twisting together the drawn out strands of fiber to form yarns, then winding the yarn onto a bobbin, or spool. The yarn is often slightly dampened during spinning, which helps prevent fly-away strands from escaping the twist and creates an especially-smooth yarn (check out this really cool photojournal of a woman hand-spinning flax).

Flax is always spun very finely--especially the longest of the fibers--resulting in a thin yarn. In order to create a thicker yarn, multiple skeins of this thin yarn can be spun together, a process called plying. You’ve probably heard this term before in reference to your toilet paper. One ply: thin and sufficient. Two or more ply: preferred! The resulting yarn (usually 3-ply or thereabouts) is typically finished by boiling for several hours in soapy water, which gives it a nice shine.

Weaving

Linen yarn is generally woven into sheets--a process wherein multiple threads are interlaced both horizontally and vertically on a loom. Occasionally, linen yarn is also knit, or formed into fabric by creating consecutive rows of loops that intertwine with one another. By virtue of these loops, knit fabrics have a degree of stretch inherent in them, and because linen yarn has no elasticity, it is quite difficult to knit and so more frequently woven.

The Rise of the Machines

This pre-industrial method of linen production hasn’t changed in centuries. Though over the last few hundred years we’ve developed machines that complete the tasks of harvesting, retting and dressing flax, these processes damage the delicate fibers such that finest linens are still manufactured almost entirely by hand. Because the process is still so laborious, even mechanized flax production actually requires a great deal more handwork than other mass industrially-produced textiles like cotton and rayon.

Check out this awesome timelapse video, called The Art and Science Linen, to see what mechanized flax production looks like today.

The Art and Science of Linen from Alex May on Vimeo.

So that's how mechanized production turns flax into linen, but where in the world is it done the best and why?

Where is the best quality linen made?

The quality of the linen fabric is greatly dependent upon the retting process. For example, as you already learned, over-retting produces a mushy, weak fiber, and under-retting makes the bits of shive difficult to remove such that the fibers can be damaged during scutching; factors entirely under the control of the retter. The secrets of flax processing have been passed down throughout cultures for thousands of years (Don’t know about the history of flax? Read about it here), and the best linens tend to originate from the enclaves within Europe that have long traditions of flax cultivation:

(The map below shows the major centers of linen production in Europe.)

  • The best quality linen is retted in slow-moving natural water sources such as streams and rivers. In fact, the highest quality linen in the world is retted in Belgium in the River Lys, though to this day chemists have been unable to determine what makes the waters so conducive to the retting process. Harvested flax is sent to Belgium from France, Holland, and even as far away as South America to be retted in the magical waters of the River Lys, which is typically crowded for miles with weighted down flax bundles.

  • Map of the European linen industryIrish linen is the best known and most valuable,  though most of the flax used for manufacturing is grown elsewhere and imported into the country for processing. The climate in Ireland is quite favorable for flax processing, and the slow Irish bleaching methods inflict minimal damage on the fibers.

  • European linens are the next finest, with the French producing the whitest and most delicate of textiles. Scotch linen is generally considered of medium quality, and German linen quality ranges from good to poor.

  • Flax is perhaps most widely cultivated in Russia and China, though the fibers tend to be of poorer quality than their European counterparts.

  • Smaller flax production centers exist in Egypt, Northern Italy, parts of Canada and the northern United States.

So you’re probably still wondering what actually makes linen fabric so magical and highly prized, even above other bast-fiber fabrics? We wondered this, too. So we decided to look in depth (read, microscopically!) at the flax plant and its mysterious awesomeness. Check out our FAQs: Mythbusting Linen: Hard Science Made Easy.

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