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The mountain shell jacket is undoubtedly the most important item in a hiking wardrobe.
The first question you should ask yourself when choosing your shell is: what kind of use will I make of it? We must ask ourselves this question immediately because not all shells have the same characteristics, which can cause their price to vary greatly. It can be said with certainty that the shell is the hiking garment where it is worth spending a little more money, but the price, and therefore the quality and technical features of the product, depend heavily on what kind of hiker you are and what characteristics you demand from your garment.
TECHNICAL MOUNTAIN SHELL: FEATURES AND WHAT YOU NEED TO KNOW
The main function of the shell is to help us in difficult moments in the mountains related to three adverse climatic factors:
- Strong wind
- More or less intense rain
- Snow
For a correct choice, it is fundamentally important to consider two key factors:
- Waterproofness
- Breathability
But what does waterproof really mean?
A garment is waterproof when the fabric is coupled with a membrane, a very thin film, which prevents water from coming into contact with the skin.
Based on this consideration, the first image that might immediately come to mind is the polyethylene bag we usually use for trash.
Polyethylene is indeed completely waterproof and does not let water through, so it would partly solve our problem, but it would create another: polyethylene is not breathable.
Why can't we use polyethylene, or plastic in general, for a hiking garment?
Our body, especially during intense physical activity, produces water vapor.
If the water vapor encounters a barrier that prevents evaporation, it condenses and returns to a liquid state, giving us a wet sensation that becomes even more uncomfortable as it cools.
A garment that does not allow breathability, i.e., the removal of water vapor from our body, even if waterproof, does not solve our problem.
How can a garment be simultaneously waterproof and breathable?
This long-standing problem was solved some years ago with a very particular reasoning.
A water molecule has a diameter of about 0.2 nanometers, so to block it, it is necessary to build a "net" that has very tiny holes, so small that they do not allow water to enter, but at the same time large enough to allow water in the form of vapor – thus with molecules smaller than 0.2 nanometers – to exit.
This ingenious, but not simple to apply, solution was achieved by creating a membrane, a very thin film produced by the expansion of Teflon, in order to build a network of conical micro-holes.
This very thin film, coupled with the support fabric through a special process, prevents water from entering while allowing water vapor to escape, making the garment simultaneously waterproof and breathable..
HOW TO CHOOSE YOUR SHELL: HOW MUCH TO SPEND?
This waterproofing process justifies a high cost for the shell.
However, there are more or less expensive garments, and a good way to help us understand this cost difference is clearly stated on the hang tag present on every garment.
On the hang tag, you will always find a very important value indicated: the water column.
Attention! The water column is found both in waterproof garments, i.e., with a column above 5,000 mm, and in water-repellent garments with values between 0 and 5,000 mm.
The water column indication is a laboratory test where a tube with a diameter of 2.5 cm is placed on a piece of fabric.
The test consists of measuring how high this water can rise in the tube before the pressure exerted on the fabric becomes so strong that water penetrates through the material.
A value of 10,000 mm, for example, means that this water column would have to be 10 m high for the pressure to be great enough for water to pass through the fabric.
Finally, let's understand how to read the water column values on the hang tag.
Here are some indications:
- 0 – 1.000 mm: The fabric is slightly water-repellent, but not suitable for outdoor sports activities.
- 1.000 – 5.000 mm: The fabric is water-repellent, but can withstand little pressure. For example, sitting on a wet bench will be enough to get wet!
- 5.000 – 15.000 mm: The fabric is water-repellent and remains so even if subjected to moderate pressure when exposed to water for a medium period; it can be suitable for highly humid climatic conditions but not heavy rain.
- 15.000 – 30.000 mm: The fabric is water-repellent and can withstand heavy rain for a prolonged period, an excellent garment.
- 30.000 mm and above: Conditions of absolute waterproofness, more suitable for a deep-sea diver than a hiker.
Learning to read the hang tag, after answering the question: what will I use my garment for? will help you make the right choice.
Indeed, it is not necessary to look for a garment with a value of 30,000 if you go for a few walks in the countryside, just as it is absolutely not recommended to buy a garment with a 5,000 column if you are used to tackling challenging high-altitude excursions.
Happy trails to everyone.
Article by Loris Giuriatti
