What Is Merino Wool?

Consider the early explorers of our planet’s farthest reaches—the hardy adventurers who climbed to remote summits and trudged to the Poles, often with minimal or barely functional equipment. Our ability to stay comfortable in harsh climates has come a long way since those days, in large part because of advances in equipment and clothing technology. One thing early explorers had right was using wool to keep warm in some of the coldest places on Earth. It’s one of the best natural insulators out there, not to mention that it was (and still is) lighter than many other, bulkier materials on the market. Of course, the wool we’re wearing today isn’t your great-great-grandparents’ wool. These days, most wool clothing is made from either regular lambswool or merino wool. While both are shorn from closely related animals, these two types of wool are surprisingly different. When you’re looking for wool clothing for your next outdoor adventure, it’s important to note the differences between merino and other types of wool—and why they matter.

1. Merino Wool Isn’t Itchy

In general, wool technically refers to hair sheared from one of many different mammals—alpacas, llamas, camels, and yaks. Most wool products you see on the market in the United States are made from sheep’s wool. But that doesn’t mean they’re all the same, because not all sheep are created equal. Merino sheep produce a type of wool that is better suited for high-performance clothing that will keep you dry, warm, and comfortable in all kinds of outdoor conditions. A primary advantage of merino is that it’s much softer than the wool of the past. Do you have any not-so-fond childhood memories of being stuffed into an unbelievably itchy wool sweater and counting the minutes until you were allowed to take it off? Merino sheep, by contrast, produce wool with exceptionally fine fibers that feel soft against the skin. Decades ago, companies began using merino to make socks. Now they’re also using it to make underwear and other base layers (clothes worn next to the skin). Unlike generations past, modern-day adventurers and active types can wear a wide variety of clothes that take advantage of wool’s many great properties.

2. Merino Wool Is Flexible

The fine fibers in merino not only make the wool soft but also allow it to stretch and recover its shape. What that means for base layers and insulating pieces made of merino wool is that they’ll move with your body. They won’t restrict your motion as you’re hiking, climbing, biking, or doing any other outdoor activity. Merino wool fibers hold their shape longer than other types of wool, so garments don’t become saggy or lumpy as quickly as older varieties of wool.

3. Merino Wool Is Lightweight

In addition to being soft and stretchy, merino is also more lightweight than many other types of wool. The diameter of a strand of wool is measured in microns. The fewer the microns, the lighter and softer the wool. The threads in a typical coarse wool garment might be around 40 microns, while merino ranges from about 15 to 24 microns. As a result, merino feels less bulky than many of its woolly cousins. For example, when you put on a T-shirt made of merino, you’ll find that it offers the same athletic fit as a shirt made of synthetic fabrics. And you can easily layer lightweight and midweight merino pieces just as you would layer synthetic clothes. While merino wool is lightweight, it still keeps you very warm. That’s because the natural crimp in merino wool creates pockets that trap body heat. When you’re outdoors in cold conditions, the wool maintains the warm microclimate immediately surrounding your body.

4. Merino Wool Wicks Moisture Exceptionally Well

To stay comfortable in the outdoors, you have to regulate your body temperature and keep your skin as dry as possible. If you get too sweaty, it not only feels uncomfortable, but in cold weather the moisture can rob your body of precious heat. That’s why it’s crucial to wear clothes that move moisture away from your skin. The crimped fibers in merino wool do just that, drawing sweat away from your skin and moving it to the outside of your garment, where it evaporates. This evaporative cooling effect prevents you from overheating when you’re biking, running, or about to top out on that fourteener.

5. Merino Provides Better Insulation When Wet

To stay warm and comfortable in the outdoors, it’s crucial to wear clothes that not only wick moisture but also provide some insulation when they’re wet. Unfortunately, some materials don’t do this very well. Cotton, for example, holds moisture and dries very slowly. If your cotton shirt gets wet, it will probably stay soggy for a while, and likely cause you to get colder. And the traditional down in your puffy jacket and sleeping bag will lose most of its insulating properties when it gets wet. Not so with wool: Whether you’re sweating or caught in a rainstorm, your wool clothes will still provide insulation and help keep you warm. The natural crimp in wool fibers does an excellent job of trapping dead air, which creates very efficient insulation. While most types of wool will insulate you when they’re wet, merino is especially effective. A piece of merino wool clothing can absorb nearly a third of its weight in moisture and still keep you warm.

6. Merino Outperforms Other Wool

If you’ve been shopping around, you’ve probably noticed that merino clothing costs a bit more than pieces made with other varieties of wool, some synthetics, or cotton. There are a few reasons for this. First, merino is a specialized, high-quality wool that isn’t produced in the same quantities as traditional wool. As a result, the limited supply drives up the cost to clothing makers. Also, because merino fibers are finer, companies must use more of it to make something that’s the equivalent weight of traditional wool. Despite the higher price, merino wool items are still an excellent investment because they simply outperform other clothes. They wick moisture, insulate the body, and flex better than traditional wool clothing. Plus, merino has a superior warmth-to-weight ratio. As the adage goes, you get what you pay for. You’ll be glad you invested a few extra bucks when you’re cozy, warm, and not itching to get out of your clothes during your next outdoor adventure. For thousands of years, people have been relying on wool to stay safe and warm while exploring the outdoors. While wool provided many benefits, its shortcomings were also significant. Fortunately, merino wool has moved onto the scene—and proven to be one of the more revolutionary developments to come along in high-tech clothing. Decades ago, it changed the way we think about socks—now it’s transforming our entire wardrobe. Written by Emma Walker for Matcha in partnership with Minus33.