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The Benefits of Merino Wool – Part 1, Water

If you’ve spent some time poking around our website, you’ve probably seen a few mentions about the amazingness of merino wool. If you’re new to merino fiber and somewhat skeptical of marketing claims (like me), maybe you take our points with a grain of salt. Or maybe you’re already a merino fan, but never really understood exactly how its such a wonder fiber. Either way, we’re betting that you like knowing the science behind things – which is why we dug deeper into the science of merino.

To recap, merino has so many benefits that it may seem too-good-to-be-true:

  1. Merino keeps you warm
  2. But also keeps you cool
  3. It’s moisture-wicking
  4. It resists water-based stains
  5. It’s antibacterial
  6. And anti-oodor
  7. And antistatic
  8. ... And anti-fire
  9. It helps you sleep
  10. It’s breathable
  11. It’s super soft (despite itchy wool sweaters of fame)
  12. It benefits your skin (yes really)
  13. It’s sustainable
  14. And renewable
  15. And biodegradable
  16. It’s naturally elastic
  17. But also resilient and strong
  18. And last but not least, it’s machine washable

How many fabrics do you know that can do all that? It seemed impossible to me too, until I understood how the merino fiber works.

Half of merino’s abilities come from its relationship with water (literally, points 1-10 above are because of this). Merino has this specific relationship because of its chemical and physical structures.

Merino wool is a protein fiber, which in the simplest of terms means that it comes from an animal (in this case, from the fleece of merino sheep). For reference, there are three types of fibers: protein, synthetic (manmade, like polyester), and cellulosic (from plants, like cotton). Merino wool, like all wool, stands out from synthetic and cellulosic fibers because its chemical structure is not consistent throughout the fiber. Wool is made up of a combination of 18 different amino acids (only 22 occur naturally), which combine in various ways to make polypeptide chains. These chains are then connected together by chemical and physical bonds. The result is that there are over 170 different proteins located in various areas of a wool fiber. That is to say – there’s a lot going on chemically with wool that allows it to have all the benefits listed above, whereas other fibers just aren’t as complicated (and have fewer benefits).

Now, back to the merino wool – water relationship. Because of the variety in its chemical structure, merino fibers have areas that are both hydrophobic (water-hating) and hydrophilic (water-loving). Furthermore, wool fibers have several “layers”, and one central layer, called the matrix, is able to hold water.

So, how does this keep you both warm and cool? Well, imagine that you are chasing your dog around the house to get your shoe back before you go to work in your merino sweater. You might generate a bit of sweat, which sits on top of your skin – but not for too long. Heat from your body turns the sweat into water vapor. The water-loving parts of your merino wool sweater suck up this vapor as if they were a straw, and store the moisture in the porous structures in the mid-layers of the fiber (called the matrix). The matrix allows wool to hold up to 30% of its weight in water before feeling wet, outperforming all other fibers in this case. But the matrix can only hold so much moisture before it “overflows” – in which case the water-hating areas work to move the moisture to the outside of the fiber (this is called wicking). The moisture is spread out over a greater surface area, where it can evaporate. This allows the cycle to continue – absorb, store, evaporate, absorb – until no moisture is left.

This evaporative action is further aided by the outer structure of the wool fiber. Wool has shingle-like, scaly outer structure. The small space between the overlap of the scales allow water vapor in and out of the fiber, aiding the evaporative process explained earlier. These scales are also covered with a waxy substance that helps repel moisture – and it’s chemically bonded to the fiber, so it won’t wash out. So, this means wool can easily release moisture, but because of its waxy covering, its harder to completely saturate wool.

Going back to our chasing-the-dog example, this means that you won’t need to change your merino sweater before going to work. Your sweater won’t be soggy with sweat, and you won’t be clammy and cold now that you’ve gotten your shoe back. You might even find that you are pleasantly warmer in your sweater.

That’s because wool doesn’t just keep you warm by keeping you “not cold”. When the moisture reaches the internal cells of the fiber, a chemical reaction occurs that produces heat. Wool fibers are crimped (due to the intertwining of the orthocortex and paracortex, which make up the core of the fiber), which create tiny little air pockets. This means that when the chemical reaction with moisture happens and heat is generated, wool can hold on to that heat.

This is also what leads to a better night’s sleep – merino helps regulate your body temperature so that you don’t overheat or over chill. This means that you don’t wake up in the middle of the night sweating or freezing, and can sleep sounder.

But what about those other benefits, like anti- bacterial/static/fire/odor/stain? Wool contains just enough moisture in its matrix that it is naturally fire-resistant and prevents the build up of static electricity. Should wool catch fire, it won’t melt, it emits less smoke compared to other fibers, and it can extinguish itself (this makes wool great for wearing around campfires). As for the anti-bacterial bit – wool may hold water in its matrix, but it also releases water when oversaturated and repels water on its surface (thanks to its waxy outer scales). This enables wool to create its own kind of microclimate where bacteria can’t thrive, as bacteria need moist, saturated environments. If odor-causing bacteria can’t thrive, then there’s also no odor - even after you’ve worn the same shirt for a week. This microclimate also means wool is better for your skin, especially if you are prone to dry skin – in fact, research has shown that eczema was significantly reduced after wearing merino wool. And stains? If they’re water-based, wool will repel it. Should some moisture seep into the fabric, wool’s hydrophobic (water-hating) areas will wick it back towards the surface, reducing the chance of a permanent stain.

Who would have thought there was so much going on between wool and water? But wool’s not done yet; it still has more to offer in Part 2.