What is Merino Wool? Understanding One of the World’s Most Functional Fabrics

What is Merino Wool
Bradley Page
Written by Bradley Page

Smooth, supple, and silky-soft: these aren’t the words that traditionally come to mind when one considers the experience of wearing woolen clothing. Memories of scratchy homemade socks gifted by relatives and heavy blankets placed on the bed during the coldest months of winter are often how we think of wool, and it’s only a slight exaggeration to say that anyone who’s ever spent a day chafing in a bristly wool turtleneck sweater knows the plight of the saints and their hairshirts.

Check out: Warmest Socks: They Serve More Than Simply Keeping Your Feet Warm

But wool does not necessarily have to be the coarse, grating garb of the repentant; the natural comfort of satiny-but-strong Merino wool has transformed our perception of this ancient fabric, making it a go-to choice for athletes, adventurers, and parents alike.

Merino wool buff

With its laundry list of attributes, this versatile fiber is the Swiss Army knife of wools, so let’s drill down into some specifics: what is Merino wool, and what makes it so very warm, wonderful, and wearable?

A Brief Background 

The very first flocks of Merino sheep are believed to have been introduced in late-12th-century Spain by a tribe of Berbers called the Marinids. Prized for its soft texture and versatility, the Merino wool industry boomed in Spain, with the country building a worldwide reputation for offering the finest fiber available.

Spain actually had a quite serious monopoly on fine wool production from the 12th to 16th centuries; in fact, if you were caught trying to export Merinos from Spain prior to the 18th century, you’d be guilty of a crime punishable by death. The country was stringent but smart about keeping such close tabs on their flocks—Merinos were a meal ticket well worth protecting.

Spain’s no-nonsense Merino mandates relaxed a bit by the 19th century. Colonel David Humphreys, the United States Ambassador to Spain, successfully imported Merinos from Portugal to Vermont in the early 1800s, bringing 21 rams and 70 ewes to America in 1802, followed by 100 Infantado Merinos in 1808.

Merino sheep in snow

Merino numbers in the United States exploded shortly afterwards; there were one million Merino sheep in Vermont by 1837, dropping the price of wool 25% pound by the late 1840s. Eventually, however, the Vermont Merino industry was run out of competition by the more efficient sheep-raising farms in the western half of the country.

Back in Spain, the Napoleonic wars that raged from 1793 to 1813 wreaked havoc on the Merino industry. Entire flocks descended from generations-old bloodlines were destroyed, ending the Spanish stronghold on the Merino business. The industry went on to gain traction elsewhere, particularly in the United States, Germany, and Australia — where the modern Merino was eventually domesticated.

These days, Merino sheep are raised in almost every country around the globe, with Australia leading the pack at producing approximately 80% of the world’s Merino wool.

Sheep Specifics 

We’ll get to why that wool is so special in a moment, but first let’s take a look at the animal responsible for supplying us with its capable coat.

Merino sheep

There are four basic types of Merino sheep:

  • The Peppin, the most prevalent strain;
  • The South Australian Merino, the largest strain, adapted to drier climates;
  • The Saxon Merino, the smallest strain, fit for the wettest climates, and producers of the whitest, softest wool, and;
  • The Spanish Merino, derived directly from the original Spanish sheep that were brought to Australia.

All Merinos are adept at foraging, and—although they can be raised for meat—their bodies are smaller than sheep bred specifically to end up on your dinner plate.

Merinos need to be shorn of their soft, finely crimped wool at least once a year, due to the fact that their fluffy fleece never stops growing. Merino wool is typically always white, but some strains will produce brown and black coats.

Merino wool white

The quality and characteristics of Merino wool depends on the strain of sheep producing it, and the fibers are categorized as superfine, fine, medium, or strong, depending on the coarseness and weight of the wool. Although the wool of any Merino sheep can be deemed as “Merino wool” by textile producers, there may not be a way to determine what strain of wool you are actually purchasing.

The Marvels of Merino 

Now that we’ve covered the Merino’s place in history and become familiar with the critter beneath the coif, let’s learn what makes the Merino’s wool special enough to have endured as a textile industry staple for hundreds of years.

Wool Facts 

Merino wool has three essential layers:

  • The first layer consists of keratin, a protein present in all animal hair that is designed to absorb moisture, therefore wicking perspiration and stabilizing body temperature;
  • The second layer is the wool’s cleaning crew, and is comprised of small, overlapping scales that rub together to remove any accumulated dirt;
  • The third layer provides the wool with a water resistant covering that will not abide rain nor sleet nor snow.

The two outermost laters of the wool fibers are actually porous, allowing sweat to make its way into the absorbent keratin core. The moisture can then be pushed back out the pores by body heat, allowing it to evaporate.

Merino wool fibre under the microscope

All in all, it’s a pretty sophisticated system for an unassuming little fiber, and it enables Merino wool to be a master of…

Temperature Control 

Unlike cotton or synthetic fabrics, Merino wool is able to retain warmth when wet, and through the physiology of its fibers outlined above, it regulates your body temperature by constantly transporting moisture away from your skin, or, if you are cold and dry, absorbing moisture from the air to warm you.

Merino can hold anywhere from 30-35% of its weight in moisture while still feeling dry to the touch, making it the ultimate fabric for extreme temperatures. The unique breathable quality of Merino wool makes it just as useful for explorers in the Arctic as it is for nomadic desert tribes.

See also: Best Base Layer: Choosing the Right Layers to Keep You Warm

In a unique experiment by the University of Otago Clothing & Textile Sciences Department in Dunedin, New Zealand, researchers conducted tests to determine how well Merino wool performed against other fabrics during physical activity.

Merino wool t-shirt

Participants in the study took to a set of treadmills while wearing garments made of one of three fabric combinations: 100% polyester, and blend of 52% Merino wool and 48% polyester, and 100% Merino wool. At the conclusion of the experiment, the researchers were able to determine that Merino wool was the champion when it came to regulating the fluctuation of body temperature that occurs during physical activity.

Participants wearing pure Merino wool sustained less physiological stress; in particular, these athletes experienced an increased lead time before sweating began and smaller fluctuations of core temperature, which not only contributes to better performance, but also increased comfort and greater physiological stability overall.

Those are impressive findings, for sure. But how did those study participants’ Merino wool garments smell after hopping off those treadmills? We’re glad you asked! Because Merino wool is…


Perhaps one of the most interesting factoids about Merino wool (and all wool, actually), is that it is naturally endowed with anti-bacterial properties which enable it to resist those less-than-savory odors that come along with physical activity or multiple wears.

Hiker wearing merino wool T-shirt

That synthetic hiking shirt might have looked appealing on the clearance rack, but it certainly doesn’t smell appealing after a day on the trail, and this can be a huge problem if you’ve on a week-long expedition without a laundromat in sight. Unless you want to haul around the dead weight of dirty laundry in your pack, you shouldn’t leave home in anything but Merino. But how does Merino wool manage to stay so clean?

The answer is in each and every Merino fiber. Unlike the smooth surfaces of synthetic fibers which attract bacteria, Merino wool fibers are scaly (remember that second layer?) and therefore make unfriendly environs for dirt. Additionally, the fact that Merino wool fibers hold absorbed moisture within the fiber is key; bacteria is unable to get to the moisture when it’s locked away within the wool.

Merino wool is also capable of an interesting process called glass transition, which allows odors to quickly become trapped within the wool fibers in extremely humid or moist environs. When very damp conditions occur, Merino wool passes through the glass transition phase, and the individual fibers become little B.O. wet-vacs, sucking up moisture and funk at an accelerated rate.

Merino wool socks

Once conditions become drier, the moisture will evaporate but the odor stays trapped until the wool is washed. Genius! Synthetic fibers are unable to pass through the glass transition phase, which is one reason why they’re far inferior to (and much, much smellier than) Merino wool. Man-made inventions may have made our lives more hygienic, but not much can improve upon the self-sufficient, self-cleaning nature of Merino.

Although Merino wool garments can go weeks between cleanings, laundering your Merino is incredibly easy to wash. Most Merino is fine in a warm or cool cycle in a washing machine, and is best air dried to avoid any shrinkage. You can also dry clean your Merino wool, but that seems quite counterintuitive to the textile’s sustainable nature.

Soft, Strong, Durable, Sustainable 

But wait! Believe it or not, there are even more impressive attributes to share about Merino wool. Merino offers sun protection! It has a UPF 20+ rating — mighty helpful if you’re taking your Merino outdoors.

Merino fights fire! Well, not exactly, but wool is the least flammable of all the fabrics, and if you happen to get to friendly with the campfire, it won’t melt or adhere to your skin like many synthetics.

Merino wool clothes near camping fire

Merino is super sustainable! It’s natural, renewable, and entirely biodegradable. If you’re looking for ways to reduce your carbon footprint, consider choosing low-impact Merino whenever possible.

Merino stops static! Merino wool is neutrally charged and retains moisture, making it naturally impossible for it to hold static. This isn’t the case with synthetics — as you’ve probably learned when donning that synthetic exercise gear in the dry, deadest months of winter.

Merino loves color! White Merino wool takes colors very well and retains dye with no problem.

Merino is mighty! In a statistic you’ve probably never even considered before, it’s been proven that wool can be bent back on itself approximately 20,000 times before breaking. To put that in perspective, cotton breaks after 3,000 bends, silk only makes it to 2,000, and rayon is even lower on the list.

Hiker wearing merino wool clothes

Wool is also surprisingly supple: when dry, wool can be stretched up to 30% of its length without breaking, and when wet, it can stretch up to 50%.

Merino can be everywhere! In addition to clothing, Merino can be used for bedding, blankets, decorative pillows, and even carpeting. Who would’ve thought one animal could help make your life so incredibly cozy?

Baby’s Best Friend 

Wee Marino lambs aren’t the only ones who benefit from that soft, versatile fleece. Merino wool has proven to be an excellent choice for baby clothes, and not just because of its soft, silky texture.

Just as it does with adults, Merino wool is excellent when it comes to regulating a baby’s body temperature, especially when its worn directly against the skin. This keeps baby dry and comfortable throughout the night—no tossing and turning after getting too hot, no whimpering and whining from being too cold—and in the event that baby gets a little, uh, moist, the wicking properties of Merino will help to keep things as comfortable as possible.

Merino clothing for babies

If you needed some more convincing that Merino wool is best for baby, consider this: a 1979 study conducted at Cambridge Maternity Hospital by Scott and Richards determined that babies who sleep on Merino wool fell asleep faster, cried less, and were better eaters and weight-gainers.

If you’re a sleep-deprived parent of a newborn, you’ve got absolutely nothing to lose and everything to gain by switching baby’s nightwear to some comfortable Merino.

To Merino or not to Merino

With all its amazing attributes and all-natural bells and whistles, it’s hard to imagine a more fantastic fiber than Merino wool. Sturdy, silky, and supremely stink-resistant, Merino wool is a perfect (and ecologically responsible) choice for everyone from athletes to outdoor aficionados to babbling babes.

Couple wearing merino wool clothes

So the next time you find yourself in the market for some new gear, keep Merino wool in mind. The fleecy flocks of Merino sheep all across the world agree: in terms of making a solid investment in clothing, you won’t find a better baa-aa-ang for your buck. Do check out our must-read article on the top merino wool base layer for more information.

Would you consider purchasing a Merino wool clothing? Or perhaps, you have a favorite Merino jacket or vest already? Feel free to share your experience with Merino clothing in the comments.


Bradley Page

Bradley Page

With several decades of experience as a backpacker and outdoor adventurer, Bradley is an open encyclopedia when it comes to gear, clothes, and other items that matter on the trail. He tested hundreds of shoes, pants, jackets, and backpacks in his long career and is always up to date with the new appearances in the niche. His experience makes him one of the authority figures in backpacking and he can help anyone to get prepared for a great adventure!