The waterproofing of a garment is an essential characteristic, particularly in seasons when showers are fairly likely. But you may well find yourself confused between the concepts of waterproofing and water-tightness, and how they are assessed. Here is a guide to help you navigate these notions easily and understand everything you need to choose your next waterproof garment for your outdoor activities.
How does a garment become waterproof?
Before understanding how waterproofing is measured in a garment, 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 chemical (which repels water). Most coated garments are very affordable, but the downside of this process is that most coatings quickly lose their waterproof properties.
The membrane technique
A membrane refers to a protective film 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 delicate and can sometimes be punctured fairly easily, even if significant progress has been made recently in developing more resistant membranes.
For regular use (as is the case with garments), membrane-based products are the better choice. Furthermore, their breathability is a significant advantage for clothing, especially for sporting activities.
What is waterproofing and how is it measured?
Waterproofing 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 waterproofing 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 point at which the first drops pass through the fabric is then determined.
The unit used to measure waterproofing is called the Schmerber (1 Schmerber equals a 1 mm water column). A fabric with a rating of 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 a hiking trip 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 are heading to a destination with a risk of heavy weather.
You should bear in mind, however, that these laboratory tests differ somewhat from real-world conditions. For example, the pressure of your backpack straps on your waterproof jacket applies pressure that reduces the waterproofing of the garment's membrane. It's the same phenomenon as when you touch the inner wall of a tent.
You therefore need to factor this in when choosing your jacket. In any case, the coating or the membrane must allow perspiration to escape, while preventing rain from penetrating.
What about wearing a fully waterproof garment?
It can be tempting to think that a fully waterproof garment will do the job. This may be the case with a waxed garment or a waterproof poncho for staying dry on a walk.
In fact, a fully waterproof garment is not breathable at all. For a few minutes in the rain it may be fine, but for a hike of several hours or several days it becomes more of a problem. You'll end up soaked by your own perspiration with nowhere to go, which is more of a hindrance than anything else.
These garments are not recommended for hiking, and even less so for any sporting activity.
An example of a waterproof jacket
This Eagle jacket, with its Active Shell waterproof-breathable membrane, is fully mesh-lined and all seams are thermally bonded. It offers a great freedom of movement while providing maximum protection against rain and wind, with a membrane rated to 10,000 mm of water and a breathability of 10,000 g/m²/24 h.
It will be perfect for sporting outings, and its resistance to abrasion and tearing is a guarantee of great longevity.
An example of waterproof trousers
This men's waterproof Quebec trousers are warm and feature a Softshell fabric with a waterproof-breathable membrane rated to 10,000 mm of water and a real breathability of 10,000 g/m²/24 h.
Its Softshell fabric combines 3 layers: an inner microfibre layer for thermal insulation, a waterproof-breathable membrane, and a highly durable stretch outer fabric to ensure excellent robustness for these trousers.
With its denim-inspired look, it is designed both for everyday urban wear with a relaxed cut, and for more active use on hiking trails.
