How to Choose a First Layer for Mountain


Any mountaineer or person who develops outdoor activity in unfavorable conditions needs protection from the elements (low temperatures, wind, rain, snow.)

That is: it needs to be hot and dry. And the latter is not only achieved by preventing rain, snow, etc. from penetrating, but also by getting our sweat to drain and not keep us drenched.

Looking for a solution to this problem, the 3 layer system was created:

A third waterproof and breathable outer layer whose mission is to prevent rain, wind and snow from entering the interior (and due to the breathability of the system, allowing moisture caused by sweat to escape to the exterior).

A second intermediate layer whose mission is to provide heat

And a first inner layer attached to the skin whose mission is to keep sweat moisture away from the body, and in some cases, cooperate in heat retention with the second layer.

The 3 layers also provide combinatorial versatility: we can use the first with the second, or the first with the third, depending on weather conditions. This already tells us enough about the 1st layer: of one type or another, more or less fine, with short or long sleeves, we will always wear one (which is not the case with the other two)

If the mission of the system is to keep the body dry and warm, it is as important that the rain does not penetrate as that the sweat does not remain in contact with the skin. So the first layer is essential; It will not help us to spend a lot of money on the outer jacket, if our sweat is not "transported" from our skin to the membrane of the 3rd layer so that it goes outside, and the clothing in contact with our body is soaked by our own humidity.


It is as important as the other two, and in many cases more important; on a day without rain, the third layer will be expendable; On hotter days, we can do without the 3rd, the 2nd, or both, but the 1st layer will always be essential, we will always wear it, and whether we are -10ºC or 30ºC, it has to work, keeping us dry, and fresh or hot, depending on the conditions.

During activity, a lot of fluid is lost. If we use highly hydrophilic fibers (such as cotton, which retains all the liquid and dries very slowly), this sweat will remain in the garment in contact with our skin. People are still seen in the mountains with a team consisting of a jacket and second layer, complemented by a cotton undershirt, which keeps them perfectly drenched. The system stops working:

The body remains soaked. It eliminates comfort, but above all, it puts us at serious risk of hypothermia in the mountains. While we are active, we overheat; the moment we stop, the sweat cools off due to the temperature and the wind, cooling our bodies suddenly and seriously.

Underwear gains a lot of weight. It's surprising, but if we weigh a sweat-soaked cotton long-sleeved shirt, we find cases where the weight gain can easily exceed a kilogram.

It is useless to spend money (quite a lot, in most cases) on the 2nd and 3rd layer, if we accompany it with street underwear, or cotton T-shirts.

The 1st layer undergarments must have 3 fundamental characteristics:

It has to dry very quickly (hydrophobic tissues)

It has to be very comfortable both in touch (material and its yarn) and pattern. Total freedom of movement, no friction of seams, no friction in sensitive areas caused by a yarn or rough fabric.

In the case of needing extra heat input, neither the weight nor any of the two previous conditions can be penalized.


The selection of the material is essential. It must be light, hydrophobic (minimal or no moisture absorption, repels it), soft, comfortable, somewhat elastic ...

2.1. Synthetic fabrics

The first technical 1st layer garments were created in the 70s. Since then, most brands have used synthetic materials for their underwear, with excellent results.

The new materials have nothing to do with the old ones: They are much softer and more pleasant, their capacity to expel water is greater, and something very important, they smell less and less. Those who tried this type of garment years ago will be surprised in this and other aspects.

2.2. Merino Wool

However, in this case, the natural, excellently worked and selected, is as effective or more than the synthetic. We refer specifically to merino wool.

We have to say that merino wool underwear is the most sold in number. Sounds strange Do you identify wool with a coarse and prickly material, which is used to make sweaters and hats? You are wrong. In fact, someone who did not know the manufacturing material of these high quality first layer garments, it is difficult to recognize it by touch, due to its extreme softness and lightness. Obviously, in this case neither itches nor weighs, with a very complex spinning and braiding work.

The advantages of this natural fabric are:

It continues to maintain its properties intact even after having absorbed 30% of its weight in water. It has the disadvantage of moistening more than synthetic fibers, due to its slower drying, but while it is wet, unlike these and cotton, it continues to heat us as if it were dry.

Dries somewhat slower than synthetic fibers, but much faster than cotton and other natural fibers. In this respect it is closer to the synthetic than to the natural.

More breathable than synthetic fibers. They can only transpire through the holes in the braid. Merino wool garments also sweat through the material.

It does not smell. We smell us, but the unpleasant smell that some synthetic garments give off is avoided.

Fire resistant: it is the least flammable of both natural and synthetic fibers, making it the safest to stick to our skin. And unlike synthetic ones, it won't melt on our skin, and will turn itself off as soon as it doesn't receive an ignition source.

Its resistance to ultraviolet rays is 50, the maximum. Greater than cotton and most synthetics.

It is antistatic. Avoid the annoying discharges that synthetic fibers sometimes cause.

Protects from cold ... and heat. It is a natural thermoregulator. In summer, the outdoor racing and mountain jerseys will keep the temperature balanced up to 35ºC. In winter, the inner layers keep us warm, but prevent excessive overtemperature.

One of the problems of merino wool is that, for it to be soft, light and effective, it requires the best wool of certain breeds and very delicate braiding, which is expensive and not available to everyone. Otherwise, the product does not work as the first layer, due to its greater roughness, less lightness, and less capacity for breathability and heat.


"Normal" garments are not prepared for activity and movement. In addition to what is mentioned regarding sweat, there is mobility, support, and friction and irritation.

The pattern of a 1st layer has to allow us to move freely, without preventing activity, and in many cases it has to exercise restraint.

You have to avoid areas that can rub and irritate us, as with the non-flat seams of non-technical garments.

The seams of the technical garments are flat, and in the case of those prepared for the mountains, they are repositioned, which supposes a totally new pattern for something as common as a T-shirt.

Why? Mainly because, due to the use of a backpack, seams can be very annoying in combination with the straps of a backpack; it is not difficult to end chafing.

Being flat, and being repositioned, this uncomfortable problem is avoided.


It is increasingly rare to see someone in the mountains (or in city, street or gym sports activities) wearing non-technical shirts: but the use of certain street briefs, boxers and panties for activity is still widespread.

It is also a mistake: it will not cause us as many problems due to excess humidity as a cotton shirt, but dry we will avoid friction and skin irritations.

Those people who often suffer from friction on the inner parts of the thighs and groin, will avoid them almost entirely with the design of these garments. In fact, it is usual that, after trying this type of garment, they decide to incorporate it into their day to day.

And of course, there is the winter theme: the long inner leggings, worn under the pants, will allow us to shelter the most exposed part of the body, due to its smaller coat. Let's think about how we wrap our upper body, in front of our legs, which can only go under a pair of pants.

Lower humidity, less problems due to skin irritation in sensitive areas.

The minimization of seams and their repositioning, the support, in addition to comfort, avoids friction, especially in the groin and upper inner side of the thighs.

Regarding the upper body, as we say, the use of technical clothing 1st layer -or only in summer, as a shirt- is already very widespread among most athletes, not just mountain. They are fundamental.

A very important top garment is women's bras. In the case of those manufactured by mountain brands, in addition to the protection and support they exercise, they dry ultra-fast, and avoid friction due to their design. They offer a great advantage over the street, even over other sports, and are very comfortable.


Although the definition of 1st layer makes sense if we consider that it is accompanied by a 2nd or 3rd layer, any garment in contact with the body can also be considered as 1st layer.

In winter, the first layers for the upper trunk are tighter (although there are more or less athletic, at the choice of each one). In addition to keeping us dry, they have different grammages that provide us with more or less thermal protection according to need, and their design, fabrics and materials are prepared to be carried with other layers on the outside.

In hot situations and in summer, we will wear t-shirts that fulfill the double function of 1st layer and outer layer. In this case, the majority of athletes, not only mountain, have gone massively to technical clothing. As we say, it is difficult to find someone in a gym, or running around town, wearing a cotton shirt. Technical garments win by a landslide.

In the summer mountains, these shirts are essential. We need the comfort, lightness and ultra-fast drying of technical jerseys for the same reasons as other athletes ... but also for some more: no matter how hot it is, it is normal for us to reach windy points in the mountains, more cold in height, that we suffer abrupt meteorological changes without the possibility of close protection, etc.

If any of these situations grab us drenched, sudden and sudden cooling can cause bodily and muscle problems.

Sweat is a defense of the body against overheating. The greatest amount of heat is released at the time of the transition from liquid to gaseous state, with evaporation. A cotton T-shirt that keeps us soaked prevents the skin from drying out, so that - in addition to suddenly cooling us when we stop - it also overheats us during activity by preventing the release of heat by evaporation.

And one more thing: if it is important to minimize friction and seams in the inner layers, it is even more necessary in the outer shirts. In this case, when carrying a backpack, the straps and the garment are in direct contact.

Source: Barrabes

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