The waterproofness of a garment is an essential characteristic, particularly in seasons when showers are fairly likely. You may well find yourself confused between the concepts of waterproofness and water-tightness and how they are assessed. Here is a guide to help you navigate it all easily and understand everything, so you can choose your next waterproof garment for your outdoor activities.
How does a garment become waterproof?
Before understanding how the waterproofness of a garment is measured, let's take a moment to look at the most commonly used waterproofing techniques in the garment industry.
There are in fact two different processes for making a fabric waterproof:
Coating
The inner surface of a fabric is coated with a layer of hydrophobic (water-repelling) chemical. Most coated garments are very affordable, but the drawback of this process is that most coatings quickly lose their waterproof properties.
The membrane technique
We talk about a membrane when a protective film is bonded to the inner surface of a fabric. The key advantage of membranes is that they are flexible, more durable and more breathable. On the other hand, they are more fragile and can sometimes be punctured relatively easily, even though significant progress has been made recently to produce more resistant membranes.
For regular use (as is the case with garments) membrane-based products are the better choice. Furthermore, their breathability is a real plus for a garment, especially for a sporting activity.
What is waterproofness and how is it measured?
Waterproofness is simply the ability of a material — a fabric, for example — to prevent the penetration of a liquid element such as water.
To measure the waterproofness level of a fabric, it is placed under a column or tube filled with water. The fabric is then subjected to the pressure of the water column, which is progressively increased.
The measurement determines at what height of water the first drops begin to pass through the fabric.
The unit used to measure waterproofness is the Schmerber (1 Schmerber equals a 1 mm water column). A fabric rated at 10,000 Schmerber can therefore withstand 10 m of water.
Given that the average pressure of falling rain is between 1,000 and 2,000 Schmerber, for hiking in light rain choose a waterproof garment of at least 3,000 Schmerber, while for a multi-day hiking trip opt for a more waterproof garment — all the more so if you're heading to a destination with a risk of heavy weather.
It is worth bearing in mind, however, that these laboratory experiments differ somewhat from real-world conditions. For example, the pressure of your backpack straps presses against your waterproof jacket, reducing the waterproofness of the garment's membrane. It's the same phenomenon as when you touch the wall of a tent.
You should therefore take this into account when choosing your jacket. In any case, the coating or the membrane must allow perspiration to escape, while preventing rain from getting through.
And what about wearing a fully sealed garment?
It can be tempting to think that a fully sealed garment will do the job. That might be the case with a waxed garment or a waterproof poncho for staying dry on a walk.
In reality, a fully sealed garment is not at all breathable. A few minutes in the rain is manageable, but for a hiking trip lasting several hours or several days it becomes a real problem. You'll end up wet from your own perspiration with nowhere for it to go — and that's more uncomfortable than anything else.
These garments are not recommended for hiking, let alone for any sporting activity.
An example of a waterproof jacket
This Eagle jacket, with its breathable waterproof Active Shell membrane, is fully mesh-lined and all seams are heat-sealed. It offers excellent freedom of movement while providing maximum protection against rain and wind, with a membrane waterproof to 10,000 mm and breathable to 10,000 g/m²/24h.
It is perfect for active outdoor use, and its resistance to abrasion and tearing is a guarantee of outstanding longevity.
An example of waterproof trousers
This waterproof Québec men's trouser is warm and features a Softshell fabric with a breathable waterproof membrane rated to 10,000 mm of water and a real breathability of 10,000 g/m²/24h.
Its Softshell fabric combines 3 layers: an inner microfibre layer for thermal insulation, a breathable waterproof membrane, and a highly resistant stretch outer fabric to ensure the durability of these trousers.
With its denim-like look, it is designed both for urban use with a relaxed cut and for more active use on the hiking trails.
