Cool wool ?

Absolute Merino wool is one of the best materials to wear when it's hot thanks to its fineness and its natural properties of breathability, anti-UV protection and thermoregulation. The latter is quite surprising: can a material really both keep you warm in winter and keep you cool in summer?

Before launching Béni last December, I wanted to test this promise and, during my last summer vacation, I only took my prototype T-shirts in Absolute Merino. Despite temperatures that sometimes exceeded 35°, I actually felt much better than in my usual clothes. And a few Bénis were enough to get me through the week pleasantly .

How is this phenomenon of thermoregulation explained?

Merino wool fiber, a true miracle of nature, is the product of a long evolution which has allowed sheep to adapt to varied climates, including the Sahara Desert and its extreme temperatures. The result is a very fine fiber, with a complex structure which gives it its multiple properties.

Comparison between a synthetic fiber and a merino wool fiber

Decomposition of a Merino wool fiber

The thermoregulation ability of merino wool is the result of two phenomena.

First of all it is explained by its insulation capacity. Wool fibers retain a large volume of air thanks to their internal cells and their wavy nature. Since merino wool is very fine, it has the most crimps (undulations) - up to 100 per inch (2.5cm). This air cushion constitutes an excellent insulating layer between our skin and the cold or heat of the outside.

The second explanation of thermoregulation is more complex. Thanks to a physico-chemical phenomenon, when wool absorbs moisture, it produces heat and cools when it releases it. Therefore, if you move from a warm room to outside where it is cold and damp, the wool captures water vapor from the air and keeps you warm. The opposite happens when you enter the warm room: the moisture from your t-shirt passes into the atmosphere and cools you down. Tiny pores allow water vapor to pass through the wool fiber. In summary, it works like natural reversible air conditioning which makes merino wool so pleasant to wear in both cold and hot weather.

What does this have to do with “cold wool”?

You may have heard of “cold wool” or Fresco? This is not a sweater that comes out of the fridge but a category of wool fabric used for making summer suits. The fact that it keeps you cool is linked to the properties of merino wool already mentioned but also to a special more spaced weaving technique which allows it to let air through better than a classic suit fabric. This type of fabric, however, is not suitable for first layer clothing (t-shirts, shirts, etc.) because it is too thick, fragile and quite rough.

June 19, 2019 — Stéphane Pinatton

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