Wool Explained

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Wool conjures images of itchy holiday sweaters and scratchy blankets for many, but this natural material has so many qualities that go underappreciated. Today we’ll take a deeper dive into wool and its origins, properties, and best uses for the dapper man.

Sheep produce most of the world's wool
Sheep produce most of the world’s wool

What is Wool?

Wool is a category of textile fibers derived from the coat of mainly sheep, but also goats, muskoxen, rabbits, camels, llamas, alpacas, vicunas, guanacos, and even cattle and pigs.

Wool’s Special Characteristics

Wool has many useful properties besides insulation
Wool has many useful properties besides insulation

While wool is grown to keep an animal insulated, it is not the same as hair or fur. Wool fibers are crimped and elastic, and they have scale, which in combination give wool it’s unique characteristics.

Wool scale
Wool scale

Crimp describes the waviness or texture of the wool, which corresponds to the fineness of the fiber. Merino wool can have as many as 100 crimps per inch. Scale is the roughness of the surface of the fiber. Hair, for example, has very little scale and no crimp, so it is nearly impossible to weave into a yarn since the smooth straightness of the hair doesn’t create grip.

Highly crimped raw merino wool
Highly crimped raw merino wool

Wool fibers have good scale, which helps the fibers attach to each other. Wool is also an elastic fiber, meaning that it resists distortion and has the ability to return to its original form.

Wool, interestingly, readily absorbs moisture while also being flame resistant. Wool is often used in contexts in which flame retardant properties are useful, such as the clothing and underlayers for firefighters.

Lanolin
Lanolin

Finally, wool contains lanolin, which is a natural wax that is produced in tandem with wool. It helps to “waterproof” sheep from the elements, preventing the wetness from reaching the skin of the animal.

For the purposes of this article, we’ll explore the history, finishing, buying, and care of sheep wool only. For more on cashmere, check out our Cashmere Explained Guide.

History of Wool

Sheep have been domesticated by humans since as early as 11,000BC, but evidence suggests that wool harvesting and weaving didn’t occur until 4000 or 3000 BC. Around 1900BC, Britain developed the ability to spin and weave. The earliest known preserved wool textile was discovered in a Danish bog, and it was dated to 1500BC.

Oldest woolen trousers ever discovered - from China
Oldest woolen trousers ever discovered – from China

The Romans wore primarily wool, linen, and leather for garments. In 50AD, they established a wool production center in what is now Winchester, UK. Despite the advances in wool finishing techniques, wool began to take on its greatest economic importance more than 10 centuries later in the Middle Ages. Annual wool fairs in cities across Europe made the wool the basis of much international trade, and wool was the primary export and economic driver of England and the kingdom of Castile.

Richard the Lionheart was ransomed with bags of wool
Richard the Lionheart was ransomed with 50,000 bags of wool

In 1194, Richard the Lionhearted of England was being held prisoner by Henry, the Holy Roman Emporer, and part of his ransom was paid with 50,000 sacks of wool; this was the equivalent of an entire year’s worth of English wool production at the time.

Weavers workshop in the 17th century
Weavers workshop in the 17th century

Wars and invasions of neighboring countries caused talented weavers to relocate or be enslaved, creating new centers of wool production. Flemish weaver migrated to England in the 14th century to avoid a Spanish invasion, while Greek weavers were forcibly sent to Italy after the Norman conquest of Greece in the 12th century.

In the Rennaissance, the Medici family built their fortune (and empire) on the wool trade. Between the 15th and 18th centuries, the wool trade was so powerful that exporting sheep was punishable by death in Spain. Spain possessed the coveted Merino breed of sheep.

One of the earliest depictions of a merino sheep by the spanish artist Murillo in 1650
One of the earliest depictions of a merino sheep by the Spanish artist Murillo in 1650

The value of wool was so powerful in Spain that it was said to have funded their extensive maritime exploration, including that of Christopher Columbus. In England, as much as two-thirds of exports were derived from wool during this period.

The Old Wool Market in Chipping Campden UK
The Old Wool Market in Chipping Campden UK was built in 1627 and still stands in the center of town

Other parts of the world also relied heavily on wool for the basis of their economy; England became a colonial powerhouse partly by building Australia’s economy on raising sheep and exporting wool. In 1797, the first Merino sheep arrived (the death penalty having been abolished two decades prior) and eventually were selectively bred to produce some of the finest wool in the world.

Australian sheep station
Australian sheep station in the late 19th century

Wool was the world’s most important textile industry in terms of volume and value until the mid-20th century and the creation of synthetic materials. New synthetic fibers were cheaper, easier to wash, and felt softer on the skin, which led to big production declines.

Polyester was king in the 1960s and 1970s
Polyester was king in the 1960s and 1970s, making clothes more affordable and easier to wash

Wool production across the world has declined by more than 50% since 1960, as land is increasingly allocated to more profitable uses such as beef and cotton growing. Even now, wool continues to lose ground to less expensive fibers in textiles and to increasing costs in the industry. Wool is predicted to become exclusive to the luxury good market unless radical changes occur to demand, production, and competition.

How is Wool Created

Wool is a very labor intensive fiber to produce. The process occurs over seven steps.

Sheep shearing by hand
Sheep shearing by hand

Shearing

The process of making wool begins with shearing the sheep, which is typically done once a year in spring when the animals no longer need a heavy coat for insulation. The newly shorn wool is called a fleece, and even though there is some mechanization available, it is still predominantly done by hand. A single fleece can weigh 6-18 pounds.

Sorting raw wool
Sorting raw wool

Grading & Sorting

Grading and sorting break up a fleece into the various qualities of fibers, which come from different parts of the sheep. The best quality comes from the shoulders and sides of the sheep, which is then used for clothing.

Scouring wool in the river in Yarra NSW Australia 1872
Scouring wool in the river in South Yarra, NSW Australia in 1872

Cleaning & Scouring

The wool must then be stripped of contaminants, which can equal 30-70% of the fleece by weight. The fibers are scoured with water, soap and alkaline ingredients.

A historic wool carding machine
A historic wool carding machine

Carding

Next, the wool is given a final cleaning and straightening by passing the fibers through a series of metal teeth. At this stage, the wool is separated into two types, worsted, and woolen. Wool for worsted yarn is stripped of the shorter fibers and the long fibers are aligned. Wool intended for woolen yarn goes directly to the spinning stage.

Spun wool yarns
Spun wool yarns

Spinning

The carded wool is then turned into thread by spinning it into a single strand of yarn. Multiple yarns are then spun together with other yarns (referred to as ply). Since wool has an excellent scale, it is easy to spin it into yarn relative to other fibers.

Weaving wool at the Trefriw mills in Wales
Weaving wool at the Trefriw Woollen Mills in Wales

Weaving

The threads are then woven into a fabric, typically in the form of a plain or a twill weave. Woolen yarns are woven into a plain weave, which results in a looser construction and a softly napped surface. Worsted yarns are woven in a twill weave, resulting in a smooth finish that is prized for its durability relative to the woolen yarn. Suit fabrics are a good example of the intended use for worsted wool twill weave.

Finishing

The process of finishing adds the final desired characteristics to the woven wool. Wool can be shrink-proofed, fulled and crabbed to interlock and set the fibers, and dyed to the desired color.

The Best Quality Wool

More than 500 breeds of sheep around the world produce approximately 1.2 million kilograms of raw wool each year. The wool can be classified based on the diameter of the individual fibers, in units of microns.

  • Fine wool <= 24.5 microns
  • Medium wool 24.6-32.5 microns
  • Coarse wool >32.5 microns

Fine wool fibers are used for clothing, while the thicker fibers are used for rugs and interior textiles. The stereotypical “itchy” wool sweater occurs when the retailer uses a larger micron diameter wool, as the rough ends of these fibers scratch the skin.

Woolens and worsteds are often categorized by a few origin-based terms:

Merino

Merino sheep
Merino sheep

Merino is a specific breed of sheep that has fine fibers. It’s the softest wool on the market, though not all merino wool is created equal. Standard merino wool is about 23 microns; fine merino around 18 microns; superfine is 16, and ultra-fine is less than 15.5 microns. The long length of the Merino fiber also makes it resist pilling better than shorter fiber wool.

Lambswool

Shearing lambs in their first season
Shearing lambs in their first season

Lambswool comes from the first shearing of a sheep at around age 7 months, when the fibers are particularly soft and elastic. It’s the rarer, higher-quality version of regular wool.

Shetland Wool

Shetland Sheep
Shetland Sheep

Shetland Wool comes from, you guessed it, a breed of sheep living on the Shetland islands. This wool is around 23 microns, making it much rougher than lambswool and Merino wool. This wool is great for heavy, warm sweaters you plan to layer over shirts.

100% Wool

This type of wool will offer you little information besides the fact that it comes from a woolly animal. It is most likely sheep, but it’s the lower quality, rougher cousin of lambswool and merino.

Wool Blends

Manufacturers often blend wool with other fibers to increase softness, make it easier to wash, or to cut costs while retaining a higher price.

Environmental Consequences of Wool

Like all natural materials, wool has an impact on the environment that you may want to consider before buying it. Wool comes from livestock, which has environmental issues such as water pollution, land overuse, and wildlife impacts. Sheep need ample grazing lands, and they tend to over-graze land in a way that pickier livestock (such as cows) do not. Like cows, sheep emit methane, which is a greenhouse gas that negatively impacts climate change. Sheep are dipped in insecticide baths to prevent infestations, which can linger in wool. Wool production requires a great deal of water, dyes, and chemicals. Some also consider the process of shearing the sheep to be cruel.

On the positive side, wool is a renewable natural material. Wool is a biodegradable material with useful environmental applications. As it degrades, wool slowly emits the nutrient nitrogen and retains water well, making it an effective substitute for other artificial turf products and some fertilizers. In the same way, wool can be used to help prevent erosion.

What Do the Super Numbers Mean?

When you buy a suit made of wool today, chances are super number like Super 100’s, 120’s or 150’s will be advertised but what is that supposed to mean?

In short, not much as it is not a legally regulated term and many weavers use their own scale. Basically, the higher the number, the finer the yarn diameter used in the fabric. Reputable weavers abide by the Fabric Labelling Code of Practice by the International Wool Textile Organization (IWTO) and you can learn all you need to know about super numbers here.

How to Buy Wool

A fine lambswool tweed in a houndstooth pattern
A fine lambswool tweed in a houndstooth pattern

Buying wool can be a frustrating experience because so few retailers list the details of materials beyond the “100% wool” tag. The more information the retailer provides, the more transparent they are willing to be about the quality of their wool. If quality is important to you, look for more rather than less information on the product description and ask sales staff for more details.

For the purposes of comfort, the finer the wool fiber, the softer it is on the skin. That being said, wool isn’t always worn directly against the skin, and it’s advisable to avoid doing so to limit the frequency of cleaning.

For woolens such as sweaters and vests, buy the softest quality you can afford. Merino is the most expensive, followed by lambswool. That being said, if you are planning to layer these garments over others, 100% wool will still be comfortable for you and your wallet.

Sources for High-Quality Wool

The market for wool products is ever-changing, so use your newfound knowledge of wool to keep an eye out for great wool products. For some reliable sources for wool products, check out these manufacturers below.

Pendleton Washable Shetland wool sweater
Pendleton Washable Shetland wool sweater

Shetland Wool Sweaters and Blankets: Pendleton

SRS in a brown turtleneck sweater
Sven Raphael Schneider wearing a brown lambswool turtleneck sweater from Uniqlo

Affordable, simple wardrobe staples in lambswool and merino: Uniqlo

WoolOvers argyle lambswool sweater
WoolOvers argyle lambswool sweater

For a range of merino and lambswool basics, WoolOvers

For a range of wool pocket squares and reversible Silk/Merino scarves, check out Fort Belvedere.

Blarney Aran Sweater
Blarney Aran Sweater in 100% merino wool

Merino fisherman and cardigan sweaters, Blarney Woolen Mills

For more, check out our extensive Sweater Guide.

How to Wash Wool

Wool does not have a reputation as being easy to wash and care for. It can shrink, pill, and become distorted if cared for improperly, and it is true that the less wool is handled, the better it will last.

Purposely shrunken merino wool sweater
Purposely shrunken merino wool sweater

The main challenge with wool lies in one of it’s prized characteristics – its scale. The grip of the fibers makes it excellent for spinning, but this characteristic also makes it difficult to maintain in the fabric’s original shape. Whenever the fabric is rubbed or agitated, the fibers grip and interlock with their neighbors, tightening or pilling the fabric. Wool also readily soaks up water, which can stretch and distort the fabric with the excess weight of the water in the material.

A typical all-in-one dry cleaning machine
A typical all-in-one dry cleaning machine

Many wool sweaters indicate that they should be dry cleaned, but this is not a good solution. Even though it claims to be “dry”, dry cleaning uses a commercial-sized washing machine and a bath of chemicals in place of water and detergent. For a thorough look at dry cleaning, check out our article.

Wool can be safely cared for at home without the need for dry cleaning. First, minimize the need to wash wool sweaters by wearing them carefully. Wear an undershirt with them to avoid contact with sweat and dirt, and fold them rather than hanging them.

For a sweater that does need washing, begin by rolling it tightly and stuffing it into a mesh laundry bag – it is crucial that there shouldn’t be any extra room in the bag. This prevents the sweater from rubbing up against itself or other clothes. Wash it on the shortest, gentlest cycle in your washer (delicate or handwash) with a small amount of mild detergent and warm water. Yes, warm water! Cold water does not activate soap, which can leave soap residue behind. Furthermore, heat increases the viscosity of water, allowing it to flow better in and out of the fabric.

Dry sweaters flat - not just the wool ones
Dry sweaters flat – not just the wool ones

To finish, never dry wool in the machine – carefully reshape it if needed and allow it to dry flat.

Conclusion

Wool may very well become a fabric only used in luxury clothing, but it has some remarkable properties that make it worth the expense. What wool pieces do you own?

Reader Comments

  1. What about the label “virgin wool?” What does that refer to other than the old joke about it coming from ugly sheep?

    1. “Virgin wool” is wool being used for the first time. It is a straight line from sheep to processing to garment. Anything else should be labeled “reprocessed wool” but likely will not be so identified in clothing.

      Virgin wool, especially in fine clothing, is usually longer fibers which generally gives a smoother softer finish. Some virgin wool, such as Harris tweed, is deliberately made with a bit rougher texture. A very fine garment can be made from reprocessed wool and that garment (all other things being equal) will usually be less expensive than the same garment made with virgin wool.

  2. Always meticulously researched, thoroughly presented, and concise. Same for the article on cotton and everything else I’ve read. A veritable Fashion Institute education in a newsletter and video.
    Thank you.

  3. Great article that you make available to your readers, especially about the care and washing- rolling it tightly and inserting it into a mesh laundry bag without any extra room and providing reasons to use warm water vs. cold. I have been doing it wrong all these years!
    The author of the article, Teresa Schneider, knows her fabrics.

  4. Interesting article.

    The caption “Scouring wool in the river in South Yarra, NSW Australia in 1872” might need revision. South Yarra is a suburb in Melbourne in the state of Victoria, not the state of NSW (New South Wales). And the Yarra River is in Victoria as well.

  5. I just picked up a few new sport coats from Jos Bank and I sometimes wear them with my Cashmere Polo Ralph Lorraine James Dean Bear sweater.

  6. Another interesting article. You mention that “Some also consider the process of shearing the sheep to be cruel”. Anyone who has watched sheep being shorn, as I have many times, will be aware that sheep love to have the burden of a heavy fleece removed. They often leap about in joy immediately after leaving the shearing shed.
    Also, if the wool is fine enough, it can be worn directly against the skin without any discomfort at all. I wear Merino undergarments by Icebreaker when skiing. They are not only comfortable, but extremely warm. And unlike polyester, they don’t smell.

  7. I have several shirts, t shirts, and underwear from Wool and Prince that are comfortable and long lasting.

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