Merino Wool. The Natural Choice of Thermal Wear and Base Layers for Outdoor Activities

Merino wool is natural and renewable and an excellent thermal wear and base layer for outdoor activities.

Merino wool thermal underwear for outdoor activities. The natural choice

The importance of base layers for mountain activities

The base layer is fundamental. Without it, the layering system does not work. Wearing a cotton undershirt will just get soaked and freeze when we stop.

On this topic and many others, we recommend you read our article on How to choose a base layer. This article is more specific and looks at the how a garments are manufactured from a natural fiber, such as merino wool. Even with the advances of the knitting process, it is still surprising that merino wool base layer clothing can feel as soft and fine as synthetic base layers and achieve excellent performance.

Merino Wool. The natural choice

Since the 1970s, when modern technical layers for mountaineering were first manufactured, synthetic fabrics have dominated this industry.

But two decades later, merino wool made a comeback, with excellent results. And it proved that, as long as this natural fiber is perfectly selected and prepared, it is as or even more effective than synthetic fibers. Nowadays it is possible to achieve ultra-fine knits with merino wool.

Do you think of wool as a coarse, itchy material used to make sweaters and hats? Well, that’s not the case. In fact, to someone who does not know which material is used to make these high quality base layer garments, it is difficult to recognize it from touch, because it is so soft and lightweight.

Nowadays, selected wool is turned into fibers that are measured in microns; the finest fibers are less than 15 microns. In addition, excellent precision has been achieved by using different types of weave, which optimizes the properties and the most suitable are selected accordingly.

And most importantly: it performs its function perfectly, not only thermally, but also as an athletic garment, by providing thermal regulation and evacuating sweat, rather than the provision of heat. The summer T-shirts work very effectively, even for sports such as trail running.

  • Cold conditions: Wool absorbs moisture, and through the sorption process, it generates heat. Its high breathability prevents overheating.
  • Hot conditions: We are cooled by the evaporative cooling process.
Running with upper and lower garments made entirely of merino wool. Photo: Devold
The benefits of this natural fabric are:

  • As we have already explained, merino wool is an excellent thermal regulator. It protects from the cold...and from the heat, provided it is made properly - it can be difficult to distinguish a merino wool technical summer T-shirt from a synthetic one in terms of how fine and thick it is. As indicated above, it is a natural thermoregulator. In summer, used as a single layer for running and mountaineering, it will maintain the body temperature balanced up to 35°C. In winter, the inner layers will keep us warm, but prevent excessive overheating.
  • It continues to maintain its properties when wet, even after having absorbed 35% of its weight in water. It has the disadvantage of getting wetter than synthetic fibres, due to its slower drying capacity, but while wet, unlike synthetic fibres and cotton, it continues to provide warmth as if it were dry. In addition, it does not feel damp to the touch.
  • It dries more slowly than synthetic fibres, but faster than cotton and other natural fibres. In this aspect it is closer to synthetic than to natural fibres.

    This middle ground between synthetic and natural fibres, gives it unique properties in the heat: as the body is cooled by sweat (which extracts a lot of heat from the body as it evaporates), synthetic fibres sometimes dry the skin too much, hindering the body's cooling function through sweating. Merino wool has good wicking capacity, but maintains a humidity that allows cooling by evaporation. It does not have the problem of humidity that affects other fibres, such as cotton, and it continues to provide warmth, avoiding sudden cooling, resulting in an excellent material for both hot and cold conditions.

  • It is more breathable than synthetic fibres. Synthetic fibres can only breathe through the holes in the woven fabric. Merino wool garments also breathe through the material. The way it works is: cotton absorbs moisture, but it does not evaporate; synthetic fibre breathes through the holes in the woven fabric, and as it is loaded with moisture it wicks away very quickly; wool however, breathes through both the woven fabric and the material itself, and wicks away sweat appropriately.
  • It does not smell. We may smell, but the odour that some synthetic garments give off is avoided. Wool garments can be worn for days.
  • Fire resistant: it is the least flammable of the natural and synthetic fibres, making it the safest to wear next to the skin. And unlike synthetics, it will not melt on skin, and will extinguish as soon as it stops receiving a heat source.
  • Factor 50 against ultraviolet rays. This is higher than cotton and most synthetics.
  • .
  • Antistatic. It avoids the annoying electrostatic charge sometimes caused by synthetic fibres.
  • Renewable and biodegradable natural material, as opposed to the need for petroleum for manufacturing synthetics, with the added problem of waste.
Devold Breeze W Hipster. Women’s fine merino wool boxer.
But wool also has its drawbacks:

  • Aesthetically, wear may leave marks on the garment.
  • Thinner and lighter garments are less durable than synthetic ones. Several brands opt for making garments from a synthetic-wool blend that avoids this problem without losing the usual performance of wool.
  • In order to make a fabric soft, light and effective, it requires the best wool from certain breeds and a very delicate and technological weaving process, which is expensive and not available to all brands. This is essential for the production of technical clothing. In addition, it requires a traceability of the wool from beginning to end that guarantees total animal welfare (extensive herds, etc.)

Devold. Since 1853

The Norwegian brand Devold is the leader for this type of clothing at Barrabes. It has been manufacturing high quality wool clothing for mountaineers, sailors and Norwegians since 1853. In fact, as early as 1888, polar explorer Fridtjof Nansen used Devold garments on his ski crossing across Greenland. Devold also clothed Roald Amundsen and his team when they reached the South Pole for the first time, in 1911.

Innovation of a material such as wool may not seem that important, if you think of garments such as sweaters. But it actually took a lot of R&D to knit with wool that was fine enough to be able to compete with the synthetic yarns used for making sports underwear and outerwear. Their garments, moreover, have different thicknesses according to need, and are extremely breathable in the underarms, back, and other areas prone to high perspiration.

To guarantee the highest quality, the wool used by Devold comes from Merino sheep, in areas with abundant water and pasture where the animals live free extensively and receive adequate shelter and care when necessary. Their ranches are located in the Argentinean Patagonia, on their website you can visit them and see in real time the natural conditions in which the animals live.
Ranch in Patagonia that supplies Devold. Photo: Devold
At Barrabes, you will also find the New Zealand brand Icebreaker, who use the wool of the extensive herds of their country with total traceability.

Kari Traa

Although all the brands we sell at Barrabes have a range for men and another for women, the Norwegian brand Kari Traa -founded by the Norwegian skier of the same name, winner of 3 Olympic gold medals- designs mountain, ski, casual and underwear (bras, briefs, t-shirts, leggings) just for women, with a very special Nordic aesthetic. And many of her garments are made of merino wool.
Kari Traa Akle L/S W, women’s merino wool base layer tee

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