Favored by athletes for its odor-limiting effect, Merino wool can be worn all year round: its comfort and warmth are welcomed in winter, its softness and durability make it a good ally for the summer.
Here we explain why this simple, natural fiber contains so many properties and, as a bonus, some tips on choosing the best garment for you!
Does merino wool stay warm?
The insulating attribute of the wool is attached to the fiber's structure, particularly suited for manufacturing warm textiles. Wool fiber is naturally curly and thin and its surface is covered with scales and has irregularities. It's this composition that makes wool a material that "inflates" and therefore traps insulating warm air easily.
Furthermore, wool is a material that "is warm to the touch". For example, in a room at a constant temperature, you will notice that wool is warmer to touch than glass which has a much smoother surface. Wool also has other thermal advantages when it is moist (rain, perspiration, etc.): absorption is exothermic which means that by absorbing water it generates a small amount of heat! All the same, be careful if you are wet in winter as this heat release is temporary so remember to add an insulating layer or windbreaker over your wool garment to trap the heat.
Merino wool fiber
Wool has an uneven surface that traps insulating warm air
The surface of flax fiber is smooth, it will have a lesser ability to trap warm air
Why are there different Merino wool weights?
As knitting enthusiasts well know: the weight stated on your wool product represents the total material weight of a fabric square meter. This gives an indication of the way in which it has been woven and therefore of its thermal performance: the heavier the weight, the warmer the fabric will stay! The weight also helps trekkers to make the best choice if they want to reduce the weight of their backpack as much as possible.
When and how to wear Merino wool, depending on the weight
- Thin, from 100 to 190 g/sqm: lightweight garment that provides moderate warmth, recommended for a warm and humid environment
- Thick, from 200 to 300 g/sqm: more durable garment that provides greater warmth, recommended for a cold and dry environment
Depending on the season or time of day, you can also go for a short-sleeved or long-sleeved Merino wool t-shirt and vary overlapping of layers.
Can Merino wool be worn in summer?
If wool traps heat naturally, isn’t there the chance of getting too hot by wearing it in sunny weather? The answer is "No"! This is down to two great properties of wool: its great ability to absorb moisture and its interaction with external conditions.
Firstly, let’s talk about its absorption capacity as wool is the champion of this! Wool is an extremely hydrophilic fiber which means that it absorbs water easily and quickly. It is estimated that it can absorb between 20% and 35% of its own weight before feeling an uncomfortable damp effect, perfect for those who want to stay warm and dry. It still releases a little heat when damp, however the reverse effect takes place when it comes into contact with warm and dry air!
This is explained by an easily observable physical process: evaporation. In effect, the transition from liquid to gaseous state requires a certain amount of heat which escapes from the fabric into the air. This process is well known by inhabitants of the desert who use it to cool the water in their fabric flask, and it's also how some of our modern air conditioners work.
In summary: water or perspiration-soaked wool loses heat if you wear it outside in dry and sunny weather due to the evaporation process. And to make it even simpler: wool can both insulate you in winter and keep you cool in summer!
However, be sure to make note: even though wool is the best at absorption, its drying ability is still slower than other materials such as polyester for example. Avoid soaking your woolen socks to cool down your feet! Also be aware that some brands offer garments made from wool polyester blend for a quicker drying time.
Merino wool: yes to warmth, no to odors!
Athletes will attest to it, a Merino wool t-shirt feels better than a synthetic t-shirt.
Although some claim that it’s because it’s antibacterial or that it reduces the spread of bacteria, in reality we haven't found any meaningful research on this subject. We may not be certain that Merino wool is antibacterial, however we do know that it reduces bad odors thanks to its absorption capacity (yes, that again)! Merino wool doesn’t just absorb the water contained in perspiration, it also absorbs its bad odors and keeps them captive within the fibers. This means that the wool reduces bad odors over several days but doesn’t eliminate them completely or permanently. And why is wool more effective than other materials? Quite simply because its absorption capacity and structure are more suitable!
In an environment at 68°F and 65% moisture, it is estimated that wool absorbs up to 18.25% of its weight in water while cotton only absorbs 8.5% and polyester (hydrophobic) 1.5%. With 100% moisture (= water poured on the fabric), the wool reaches over 30% absorption capacity.
Is Merino wool a durable material?
Many structural reasons can explain a fiber’s strength.
One of these is the length of the fiber: the longer the fiber, the less "fiber ends" there are in the fabric weave and therefore there is less risk of breakage at the seams joining two fiber strands. Another reason is the elasticity of the fiber: if it is stretchy then it better withstands the different pressure placed on the weave.
You guessed it, wool fulfils these criteria hands down! Its fiber is naturally long (more than cotton for example) and it has a "curly" or "crimped" composition which gives it great stretch as it can stretch out up to around 30% of its length without breaking. In addition, the twisting and crisscrossing of fibers during the yarn creation also contributes to the strength of woolen fabric.
Nevertheless, be aware that wool isn’t the most durable material. Some synthetic materials are more durable although they don’t have the same benefits as wool (warmth, odor control, stretch, etc.).
That’s why it’s not unknown to find wool garments reinforced with polyamide yarn that covers the wool for extra durability.
Naturally curly wool is an extremely long fibre with less weak points once spined
Polyamide yarn covers the wool strand for greater durability
The softness of merino wool
Do you have a bad memory of an "itchy wool" sweater? Think again with Merino wool!
First and foremost, you must understand why standard wool itches: it's a question of the thinness of the strand and hairiness of the wool. Remember that wool has an uneven surface that traps insulating warm air. The scales can then grip the skin and create an uncomfortable tingling feeling.
Moreover, if the wool strand is thick, it loses flexibility and it touches the skin more during our different movements, increasing the gripping points and itchy feeling.
Now for a little bit of history: the Merino sheep is a breed of Spanish sheep, whose ancestors have been selected from generation to generation, for the thinnest wool possible. The thinness of the wool from Merino sheep gives it great flexibility, which means less skin contact and a soft, comfortable feeling.
As a comparison, the thinness of Merino wool varies between 16 and 19 microns, whereas that of standard wool is between 20 and 25 microns and a hair is between 70 and 120 microns. In the photo below, you can see the thinness of a fiber of Merino wool on the left, compared to a human hair on the right (Photo credit: ©CSIRO).
However, it should be noted that for extreme softness, it's better to go for a fabric made from very smooth fibers that don't grip to the skin.
Merino wool is renewable
To avoid any misunderstanding, it's important to properly define what we understand by "renewable". A renewable material is one that has the ability to regenerate itself naturally: wood, cotton, rubber, wool, etc.
This is in contrast to non-renewable materials whose quantities are limited because they can’t regenerate on a human timescale: iron, charcoal, oil, sand, etc.
As well as being renewable, we are guaranteed that the Merino wool used in our products is ethical. Our supply comes exclusively from a livestock farm in South Africa where we are assured that:
- living and shearing conditions are decent
- the painful practice of mulesing is prohibited
It is however important to highlight that although wool is renewable, breeding animals can generate a significant amount of CO2. If you want to reduce your carbon impact as much as possible, you can switch to recycled materials. It should also be noted that pure wool (untreated and without synthetic backing), such as hair, is biodegradable but it decomposes over very long periods of time, especially in the absence of air (eg: buried). It is therefore not recommended to add wool to your compost.
In summary: how do you choose a Merino wool garment?
To make the best choice, assess your needs in terms of warmth and analyse your practice environment: heavy weight and a long garment in cold and dry weather, light weight and a short garment in hot and humid weather. Also be aware that Merino wool is a perfect first and second layer for the 3-layer technique.
If you already know that your garment will be really put to the test, go for Merino wool blended with a more durable fiber and reinforced inserts on friction areas.
If your trek is forecast to be rainy or if you think you won't have much time to dry your clothes after washing, go for a garment made from Merino wool and synthetic to reduce drying time.
Movement and flexibility
If freedom of movement is your priority, choose a garment made from Merino wool and elastane for greater stretch and comfort.
If your body is prone to heavy sweating, choose garments with mesh inserts on perspiration areas to stay dry and for added comfort.