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How It Works: A Waterproof Jacket

It's dripping with science.

It's got decades worth of technology packed into every inch, it's resistant to one of Earth’s most terrifying elements, and—here’s the kicker—you’re wearing it. Most people don't think twice about the raincoat hanging in their closet, but if you step back and really analyze it, you’ll be amazed at just how much knowledge it takes to create one of these things (and keep it from feeling like a sauna on the inside). We recently spoke with the tech team at Sierra Designs to figure out just how a waterproof jacket works.  

Men's Fitness: How do you make a jacket waterproof?

Sierra Designs: There are several ways to make a jacket waterproof. One is by constructing it out of PVC, like a traditional yellow raincoat. Since PVC is not breathable, these jackets perform poorly in situations where you are active and generating sweat. The second technology is a waterproof/breathable membrane built into the jacket. Membranes made from polytetrafluoroethylene (PTFE) have microscopic pores that are large enough to allow water vapor from your body to escape, yet small enough to prevent water droplets from getting inside.  Polyurethane (PU) membranes absorb moisture from inside the jacket, later releasing it as water vapor on the outside. These membranes are far superior to PVC, and great for activities like hiking and skiing.

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What’s the difference between waterproof and water-resistant?

Simple explanation: What is typically referred to as waterproof incorporates some sort of membrane (PTFE or polyurethane) built into the jacket. Water-resistant is typically a treatment applied to the exterior of the jacket to keep water from soaking in. Waterproof jackets will stay drier longer, while the water that hits water-resistant jackets will eventually soak through.

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Can the efficacy of a waterproof jacket fade over time? If so, is there a way to get it back to "like-new" status? 

Yes and yes. Most of these jackets are made with a durable water repellant (DWR) treatment that is applied to the exterior of the jacket to help water bead up and roll off.  DWR treatments will wear off over time, but there are different washes and treatments on the market that can help restore DWR performance. 

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