What is Wool? And What Makes The Perfect Sweater?

what is wool

New to the fashion world? Welcome :) To help catch you up to speed, virtue + vice is offering free mini-courses. We will be releasing a new chapter bi-monthly. The courses will take you from the very first step in the fashion supply chain, textile fibers, all the way through to the finished product in stores. Our first crash course is TEXTILES 101. The third topic of TEXTILES 101 is Animal Fibers, specifically - what is wool?

Get ready to learn everything there is to know from sheep to ugly Christmas sweaters, including animal treatment and cruelty-free options.


Wool is a generic term for animal fibers.

Wool doesn’t just come from sheep. It comes from other animals too, like goats, camels, and rabbits. When you break it down, wool is made of proteins and lipids (fats). A quick refresher from the last course, plant-based natural fibers are made from cellulose.

What is Wool, quality standards

There are few things to consider when it comes to the actual quality and value of wool. What characteristics determine what is wool 's value? They are fiber diameter, crimp, yield, color, and fiber staple length/strength. The fiber diameter measures the width of the fiber.

Fiber widths

Are measured in microns (μm), which are one one-millionths of a meter. In wool the finer (smaller) the diameter the higher the quality of wool. This is because finner fibers can be spun into finer yarns, which generally create fabrics with more luxurious hand feel and drape. Not only is the diameter important when evaluating wool, but also the uniformity of it. Having a wool blend with different size fiber diameters is a bad thing. We want them all to be about the same width. That is why the average fiber diameter is extremely important when appraising the value of wool.


Is the natural kinks and waves in the fiber. As a general rule, finer fibers tend to have more crimp than thick and coarse wool fibers. With crimp, what we are looking for is uniformity. Fibers with even crimp throughout the fiber length have a higher value than irregular crimp.


Historically, dark color fibers have been undesirable and are sold at a lower cost. This is because darker colors are harder to dye. Fibers that are light colors, or even better, white, are easiest to dye.

But, the sustainable fashion movement has disrupted the wool fiber market. Dark fibers and fibers with color are a growing niche market share. Naturally colored fibers offer color and variation without needing to use harsh chemical dye processes. By eliminating dying and using the fibers natural colors, we are able to eliminate one of the biggest causes of water pollution in the fashion industries supply chain.


Lastly, wool that is strong is most desirable. Processing wool is harsh on the fibers. And, wool fibers that can withstand the beating of being made into a sweater without breaking have a higher value because they create a better quality product.

What Causes Itch Keeps Us Warm

Wools warmth comes from a triple threat of fiber characteristics.


Slow moisture absorption. The secret to clothes that keep you cool when you work out is quick moisture absorption. When clothing pulls moisture from your skin quickly, it creates a cooling sensation. Wool has slow moisture absorption. It absorbs so slowly, that it does not create a cooling effect on the skin. But, it absorbs fast enough that it is effective in keeping skin dry and less prone to feeling cold.


You know how birds ruffle their feathers? When they do this they are trapping small pockets of heat in their feathers. These small air pockets help to insulate them. The same principle applies to wool.


The crimp (natural kinks) in wool creates spaces for tiny pockets of air to become trapped, creating natural insulation.


On a microscopic level, wool has tiny scales on the surface of the fiber. These tiny scales are evolutionary and what help to keep animals (and humans when we wear wool) warm. The small microscopic scales also trap tiny pockets of air just like the crimp does. And, these air pockets are what create extra bulk and warmth in the fabric. The only downside is that these scales are also itchy on the skin.

Yes, wool can be itchy. But, as I said earlier, all wool is not equal. Wool that has a finer diameter is generally less itchy. When fibers are too short they poke out of the yarns and cause irritation to the skin, the longer the fiber the less chance of this happening.

But, even with the finest of wool fibers, it will always be itchy because of the inherent micro scales on the surface of the fiber that tend to irritate many people who have sensitive skin.

what is wool? photo of wool under a microscope

Now onto the most popular type of wool, the kind that comes from sheep

Let’s start with the most popular wool on the market today, sheep’s wool. There are lots of different types of sheep's wool, the most popular it Merino. To learn more about alternative kinds check out this article.

About 2 million tonnes of wool are produced annually, and 60% of that goes into apparel. By weight, China produces the most wool than anywhere else in the world, followed by Australia, and then New Zealand. Australia although second to China is still considered the world's leading producers of wool (worth $3 billion) from its upward of 70 million sheep. A single sheep can produce anywhere from 2-30 lbs of wool per year.

What is Wool? - A History

Did you know that sheep didn’t always have wool? Before 10,000 BC (before domestication), humans would hunt sheep for their meat. Up until that point, sheep had a short and thick fur coat similar to that of deer. With the domestication of sheep, people started using them for their milk and making cheese, not just meat. The skin was made into leather. And, often the deer like fur on the hide was left on to increase warmth.

People started noticing that the hair around the sheep's stomach and the underside were longer and finer than the rest of the animal. And, that fiber could be used in yarn spinning. People then began selectively breeding sheep to produce the best and longest hair in the hopes of creating an animal with hair that could be spun into yarns and textiles. And, by about 5000 BC people were able to use sheep's hair to spin wool yarn.

Man created the modern sheep.

What is Wool 's Advantages?

Wool has many advantages over plant-based fibers. The biggest advantage is warmth. I guess that could be a disadvantage if you are in an extremely warm climate near the equator. Wool, because of lanolin - which is a natural oil from the animal skin, is also water resistant. Lastly, wool is fairly easy to dye so it comes in a vivid range of colors which is great for designers. We will explore more about the types of dyes used in a few weeks in our DYE chapter - if you want to learn more, make sure to sign up for our email list for course updates.


What is wool used for? Besides clothing, wool has quite a few industrial uses, from piano dampers to the inside core of baseballs, to absorbent pads for those baaaaad oil spills.

What is Wool 's Unsustainable Secret?

When it comes to wool, media and activists usually get caught up on the animal rights issues. But, there is more going on in this animal fiber supply chain. But, what is wool 's less talked about the unsustainable secret?

The tiny scales mentioned earlier that keep us warm, are also the reason wool cannot be machine washed. During washing, the tiny scales stick together and cause the fibers to clump and felt.

Chlorinated wool was invented to try and combat this itchiness and shrinkage that is inherent to animal fibers. Basically, wool fibers are submerged in a chlorine bath. The chlorine bath chemically removes the scales from the fiber but leaves the rest of the fiber intact. We then have itch-free, machine washable wool.

Chlorinated wool is not new. It has been commercially available in almost all wool manufacturing since 1893 when taught in Loewenthal’s “A Manual of Dying”.

Why is chlorine bad?

Chlorine on its own is not necessarily the issue. Actually, it kind of is. High exposure to chlorine has left workers with symptoms like pain, redness, and blisters on the skin, as well as coughing, and a burning sensation in the nose, throat, and eyes.

Chlorine creates even more problems mixing into textile wastewater. Without treatment, chlorine bonds with carbon and creates adsorbable organic halogens aka AOX, which include dioxinThere are lots of different types of AOX, but we are mostly concerned with dioxins. Dioxins are card-carrying members of the dirty dozen - a group of particularly aggressive organic pollutants. AOX creation also happens in the production of vinyl, in dry cleaner fluids, household bleach, paper processing, and other industrial manufacturing supply chains.

Dioxin is -
  • a known carcinogen
  • an endocrine system disruptor in humans and wildlife
  • not able to break down easily in the environment



Look for boiled wool

The processes of boiled wool originate as far back as the Middle Ages. Boiled wool is a type of felted wool similar to non-woven felt fabric.

First, the yarn is knit into fabric. The fabric can be dyed, or left in its natural color. Then, the fabric is boiled in hot water and alkaline soap, this process is called fulling. The boiling causes the scales of the wool to stick together creating a felted fabric. The process creates a denser fabric, and up to 50 percent of the fabrics dimensions can be lost from shrinkage during this process. Because the scales are all stuck together from the fulling process, the fabric tends to be less itchy.


Eileen Fisher is working on new technologies to eliminate the use of chlorination in wool with the help of bluesign. The fall of 2015 was the release of their first season of chlorine-free wool. Here at virtue + vice, we are happy to see Eileen Fisher leading the way. Convincing mills to change their systems is costly and time-consuming. When large industry thought leaders push for these changes they open the gates for smaller companies (who can’t afford expensive research and development) to join the sustainable fashion movement.

For more on what is wool 's environmental impacts from chlorination, check out this report by Patagonia.

Athletic Wool is kind of a Hoax

Today wool is a performance fabric, thanks to some clever marketing. The companies using wool boast that their fabrics are naturally breathable, water resistant, are great at wicking, help to regulate body temperature, and are odor resistant. This could be true if the fibers are without treatment. So, what is wool 's real performance characteristics? 

The sad reality is that the fibers undergo so much processing, they lose all of their natural characteristics. Let’s break down what you are really buying when you buy performance wool.


Yes, wool, even treated wool, will be more breathable than synthetic alternatives.

Water resistance

The natural animal oil lanolin is what gives wool it’s natural water resistance. When wool goes through the harsh dye process the lanolin is washed away. Leaving the wool without its natural water resistance coat. Companies that claim to have water resistant wool are lying. They are most likely using treatments, that are often toxic. These chemical fabric finishes create man-made waterproofing. Some companies that are especially eco-friendly are skipping the chemicals and re-applying a natural lanolin finish after dying to restore the fibers natural water repellency. If you want true, natural water-resistant wool, try buying oiled wool. Processing of this type of wool is done only in cold water to keep the wools natural lanolin.

Wicking and body temperature regulation 

While wool is technically moisture-wicking, any brand that claims that it is just as efficient or, even more, efficient than a petroleum synthetic fiber like polyester is lying. Here is why. While wool is very good at wicking, it is also pretty decent at absorbing. The outside of a wool fiber is made of fatty acid proteins and, that does not absorb liquid very well. However, inside the fiber, there are salt linkages, and they are great at absorbing moisture that is in vapor form - like sweat.  

Petroleum fibers like performance poly do not absorb moisture vapor the way wool does, so they wick 100% of the moisture away.

Odor resistant

This claim also comes from lanolin. Lanolin is great at preventing bacteria (which causes a bad smell in clothes) from forming and growing. This is why oily Merino fabric doesn’t need washing and will still stay fresh and non-stinky after continued use. So, if the lanolin is lost during the washing process, so are the properties that keep you smelling fresh.

Some brands say that because Wool will absorb moisture, it keeps you from sweating, and this, in turn, reduces body odor. I mean, isn’t that the same for every single natural fiber? They ALL absorb moisture. A generic statement like this isn’t specifically applicable to wool and seems like false advertising.

Animal Treatment


Mulesing is one of the most controversial practices in wool production. The practice of mulesing removes strips of skin from around the buttocks of a sheep. This is to prevent the parasitic infection of flystrike (myiasis). The theory is that the wool around the buttocks can trap feces and urine, which will then attract flies.

By skinning the animal's buttocks, scar tissue grows back that cannot grow hair that will trap feces - preventing flies and illness.

It's controversial. The National Farmers Federation of Australia argues that "mulesing remains the most effective practical way to eliminate the risk of 'flystrike' in sheep" and that "without mulesing up to 3,000,000 sheep a year could die a slow and agonizing death from flystrike".

Is this really an ethical way to treat animals?

No. But, it is the most cost-effective way to treat animals.

PETA advocates for better animal management systems. “Mutilating sheep is not just cruel; it’s also ineffective. Better husbandry is the answer, not mutilating animals. Prevention of maggot infestation through humane methods such as diet regulation, spray washing, and simply breeding types of sheep with better traits for the Australian climate is possible.

peta sheep ad no mulesing 

Is Organic Wool A Solution?

Organic wool certification, only certifies that the animal treatment is within to organic standards. It does not certify the processing of the wool, which includes the treatment of the animals during shearing. Basically, all it means is that the animal if eaten meets organic standards.

  • Feed and forage for the sheep from the last third of gestation must have organic certification.
  • There are no synthetic hormones or genetic engineering of the sheep.
  • No synthetic pesticides on pastureland or use of parasiticides, which can be toxic to both the sheep and the people.

Ethical wool/ cruelty-free wool

The Responsible Wool Standard

As this report from PETA shows, sheep can be kicked, beaten, stuck with clippers and slammed against floors as shearers wrestle with them to shave the wool off their bodies. The Responsible Wool Standard “aims to prevent these practices through regulation, audits, and certifications”

The Responsible Wool Standard states -

The Responsible Wool Standard is a voluntary global standard that addresses the welfare of sheep and of the land they graze on. The certification is an independent, voluntary standard. On farms, the certification ensures treatment of sheep with respect to their Five Freedoms and also ensures best practices in the management and protection of the land. Through the processing stages, certification ensures identification and tracking of wool. There is annual auditing by an independent third party certification body. As certified wool from these farms moves through the supply, the Textile Exchange Content Claim Standard is used to provide a chain of custody system to the final product. Each stage of production is certified to this standard by an accredited third-party certification body.”


Personally, I have never been much of a fan of certification systems, even third-party ones. I have seen too many organizations doing the wrong thing pay their way into getting certified. That is why I think FiberShed is a much better solution to ethical and cruelty-free wool


Fibershed is amazing because it pools the resources of small farmers together so they can collectively act with power. I think we all agree that slow fashion is the answer to fast fashion. And, part of slow fashion is working with small local farmers. 

Fibershes website states -

“Fibershed develops regional and regenerative fiber systems on behalf of independent working producers, by expanding opportunities to implement carbon farming, forming catalytic foundations to rebuild regional manufacturing, and through connecting end-users to farms and ranches through public education.

We envision the emergence of an international system of regional textile communities that enliven connection and ownership of ‘soil-to-soil’ textile processes. These diverse textile cultures build soil carbon stocks on the working landscapes on which they depend, while directly enhancing the strength of regional economies. Both fiber and food systems now face a drastically changing climate, and must utilize the best of time-honored knowledge and available science for their long-term ability to thrive.”


And, what would any article about what is wool be complete without a mention of PETA? To learn more about PETA’s beliefs on the wool industry check out their website. It is my opinion that while PETA does a lot of good and is great at creating press around animal rights issues, they are a bit too radical of a group for me to throw my full support behind.


If there is something we forgot that you want to learn about let us know in the comments section.

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