What Is Merino Wool? Nature's Technical Fibre

By Mark Roberts

Naturally breathable, temperature regulating, odour resistant, warm, lightweight and comfortable to wear? Pah. We don't baa-lieve the hype. You can't pull the wool over our eyes. 

No, honestly, it's true! Merino wool is a certified wonder fibre. It’s so good, it even outperforms synthetic fabrics in many situations. But what actually is Merino wool? How is it different to regular wool? And what makes it such a good material for bouncing about in the outdoors?

The Benefits of Merino Wool

  1. What is Merino wool?
  2. Where does Merino wool come from?
  3. How is Merino wool different to regular wool?
  4. What are the benefits of Merino wool?
  5. What is non-mulesed Merino wool?

Woman bouldering in merino wool in Slovenia

What is Merino wool?

Merino wool is a specific type of wool that comes from the Merino breed of sheep (well, it’s ‘breeds’ really but let’s not complicate things!). Wool has to be finer than 24 microns (a measure of fibre diameter) to be classified as Merino (more about that later).

Where Does Merino Wool Come From?

Merino sheep originated in Spain but they’re now bred all over the world. Most of the world’s Merino wool currently comes from Australia and New Zealand (we exclusively use Australian Merino wool).

How Is Merino Wool Different To Regular Wool?

Merino wool fibres are much finer than standard wool fibres which is why Merino sheep became such a prized breed. Merino fibres are so fine, they’re around 1/10th of the width of human hair! This fineness is one of the reasons why Merino makes such a good material for outdoor clothing.

What are microns?

The diameter of wool fibres is measured in microns (μm) with each micron being one millionth of a metre. As a frame of comparison, the Merino wool we use is 17.5 microns, while lambswool is usually around 25 microns. The smaller the fibre diameter, the finer the Merino and the softer it feels.

< 17.5 microns Ultrafine
17.6 - 18.5 microns Superfine
18.6 - 19.5 microns Fine
19.6 - 20.5 microns Fine medium
20.6 - 22.5 microns Medium
22.6 - 24.0 microns Strong

Hiking in the French Alps in Merino wool base layers

What are the benefits of Merino wool?

Soft and prickle-free

Because they're so fine, Merino wool fibres are much more flexible than standard wool fibres. This means that the ends of the fibres bend where they touch your skin, rather than sticking in and creating the prickly, itchy feeling you often get with coarse wool jumpers.

Faster drying

Merino fibres – particularly the ultrafine 17.5μm fibres we use – produce much lighter fabrics that absorb less moisture and dry quicker. We’re able to make fabrics this light because of the natural resilience of wool fibres to flexing, bending and stretching.

High warmth-to-weight ratio

Wool fibres have a natural waviness to them called ‘crimp’. It’s this crimp that makes wool so warm by creating lots of pockets of insulating air when the fibres overlap. The finer the fibres, the greater the crimp and the more air pockets that are created. This gives fine Merino wool an unrivalled warmth to weight ratio. Crimpety crimpety.

Breathable and wicking

Wool is naturally breathable. Unlike synthetic fabrics, it’s capable of absorbing moisture into its own fibres, before releasing it to the outside. Wool can absorb up to 35% of its own weight in water before it starts to feel damp, holding moisture away from your skin to keep you dry and comfortable. And when it can’t absorb any more moisture, wool will mechanically wick sweat as well.

Cycle touring in Slovenia in a Merino wool cycling jersey

Temperature regulating

Wool controls your temperature by slowing down or speeding up the rate of evaporation of the moisture held in its fibres. When you warm up, it releases more moisture to cool you down. And when you get cold, it slows down this evaporation. By working at a fibre level, wool keeps you comfortable across a wider range of temperatures.

Odour resistant

Because it’s so breathable, wool prevents the warm, moist conditions that odour-causing bacteria thrive in. On top of that, wool can also absorb odours into its fibres, only releasing them in washing. This means you can wear Merino wool clothing for days without worrying about offending anyone’s nostrils!

Insulates when damp

Wool has a natural elasticity from the crimp in its fibres. When wool gets wet, this bounce stops the fibres from collapsing and losing all those insulating air pockets. You’ll still lose heat through conduction, but it means wool will keep you warmer in damp conditions than other fabrics


Merino wool is completely natural and renewable, requires less frequent washing (reducing water and energy consumption) and is completely biodegradable at the end of its life.

Bouldering in a Merino wool base layer

What is Non-Mulesed Merino Wool?

Mulesing is a method employed by some farmers to prevent the loss of sheep to a parasite called flystrike. It involves removing strips of skin from around the sheep’s bum to stop wool growing in that area, getting dirty, and attracting the insects that cause the infection.

There are much kinder ways to protect sheep from flystrike, such as regular shearing. These kinder methods are a little more expensive, but we reckon it’s worth it to avoid using this practice. That’s why all Alpkit Merino wool clothing comes from certified non-mulesing farms. So you can rest assured that any Merino product you buy from Alpkit came from a sheep that got a regular wash and trim rather than the cheaper, grim alternative.

How We Use Merino Wool

Merino wool's incredible combination of properties means that it makes a fantastic base layer material. Its breathability and temperature regulation keeps you comfortable across a broad range of temperatures. In winter, a high warmth-to-weight ratio allows you to boost your layering system for very little extra bulk (including your extremities with liner gloves and hats). And, where most base layers would send our odour-ometers into overdrive after a few days of backpacking or cycle touring, Merino wool stays fresh for days. It's no wonder Merino sheep have made a home everywhere from the Aussie outback to the New Zealand highlands!

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