When you’re out on a run or enjoying a hike in the great outdoors, the last thing you want to worry about is getting drenched by a pop-up rain shower or thunderstorm. Luckily, after putting on your waterproof jacket, you’ll feel the sense of relief pass over you as you run back to shelter without your torso feeling wet and cold.
Taking time to reflect, however, you may begin to wonder just how the jacket manages to keep all the moisture out—even the sweat beneath the jacket. If you’ve ever been curious about how waterproof jackets and fabrics work, we’re here to answer those burning questions.
The outer fabric of your waterproof jacket isn’t a single layer of fabric at all—it’s two or three layers of materials that all perform different jobs to keep the outside liquid moisture out and draw the inside vapor moisture away from the body. The three porous layers that form waterproof fabric include:
A waterproof fabric’s outer layer is the one that you see on the outside of the jacket. Typically, jacket brands craft this layer out of nylon or polyester and coat it with a durable water repellant (DWR) to make the material hydrophobic. This coating helps to bead water droplets, preventing them from soaking the material and improving the jacket’s overall breathability.
As the face layer ages, body oils can wear down the DWG, and the jacket’s waterproofing can suffer. When this happens, you can renew it by washing the jacket and applying a new coating of DWG.
The second layer, or membrane layer, is the fabric that allows vapor to leave and restricts water droplets from coming in. This membrane has microscopic pores that aren’t big enough for liquid water to penetrate but are big enough for water vapor—from your sweat—to escape.
Without a third layer, the two previous layers work to give the wearer more breathability and airflow. The negative aspect of a two-layer waterproof fabric is that the pores will clog from the wearer’s body oils quicker and require more frequent washing. You may also notice that the jacket doesn’t keep you as warm in windy conditions.
With a protective third layer—called a “scrim”—body oils are slower to reach the membrane layer. This type of jacket will keep you warmer and require less cleaning than a two-layer waterproof fabric.
With this knowledge of how waterproof jackets and fabrics work, you may wonder how to apply that to your shopping experience. Manufacturers measure waterproofing with the number of millimeters (mm) of water a 1-inch square of the fabric can handle before leaking while under pressure. The higher the number, the more waterproof the fabric.
Brands measure breathability in a similar fashion using grams (g) of water vapor that can move through a square meter of waterproof fabric over 24 hours. Again, the higher the number, the more breathable it is.
GORE-TEX® waterproof fabric is one of the most famous and reliable materials in the industry—used by big name brands such as The North Face and Arc’Teryx. If you’re searching for the perfect waterproof jacket this season, check out Escape Outdoors’s selection of high-quality Arc’Teryx and North Face clothing for sale, and search for the jackets with GORE-TEX® technology.
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