Favoured by athletes for its odour-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 fibre contains so many properties and, as a bonus, some tips on choosing the best garment for you!
It’s no accident that our grandmothers recommend "a little wool" when it's cold!
The insulating attribute of the wool is attached to the fibre’s structure, particularly suited for manufacturing warm textiles.
Wool fibre is naturally curly and thin making it very hairy. 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.
Moreover, 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.
As knitting enthusiasts well know: the weight stated on your wool product represents the total material weight of a fabric square metre.
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.
There are two types of 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.
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 fibre 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!
A small precaution all the same: 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 woollen socks to cool down your feet! Also be aware that some brands offer garments made from wool polyester blend for a quicker drying time.
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 odours thanks to its absorption capacity (yes, that again)!
Merino wool doesn’t just absorb the water contained in perspiration, it also absorbs its bad odours and keeps them captive within the fibres.
This means that the wool reduces bad odours 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 20°C 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.
Contrary to popular belief, bacteria are not entirely responsible for bad odours (well, not completely...).
Firstly, know that perspiration produced by the human body's sweat glands is odourless. However, this perspiration is made up of molecules where bacteria that are naturally present on the human body will thrive. These bacteria (which mostly respond to the sweet name of staphylococcus hominis) will break down the sweat molecules with the help of an enzyme. It’s this enzyme and the residue left by the bacteria once the sweat molecules have decomposed that create the bad odours!
Many structural reasons can explain a fibre’s strength.
One of these is the length of the fibre: the longer the fibre, the less "fibre ends" there are in the fabric weave and therefore there is less risk of breakage at the seams joining two fibre strands.
Another reason is the elasticity of the fibre: 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 fibre 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, odour 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.
Do you have a bad memory of an "itchy wool" sweater? Try 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.
On the photo opposite, you can see the thinness of a fibre 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 fibres that don't grip to the skin.