Restore Water Repellency

January 1, 2009

It’s like a force field around your new rain jacket, an invisible defense system that repels water so vigorously it almost sizzles on contact. Unable to penetrate your armor, the droplets bead up, roll off, and leave you deliciously dry underneath. But time, use, and abuse wear down your jacket’s protection, until one day you notice that it’s sucking up cloud-borne invaders like a traitorous sponge. Time to rebuild your defenses!

  Manufacturers apply a chemical treatment to fabrics used in rain gear and other outdoor equipment, including tents, packs, and sleeping bags. Known as a durable water repellent, or DWR, this hydrophobic coating is the magic stuff that causes water to bead up and smoothly slide off. It also prevents the underlying fabric from getting wet. This last feature is crucial for maintaining a garment’s breathability, or its ability to pass water vapor (i.e., your sweat) from the inside out. Unfortunately, DWR wears off with time and use, especially in high-abrasion areas like those under your shoulder straps or waist belt.

DON’T WET OUT   As DWR fades away, your jacket starts to get wetter, faster. And once it becomes saturated—a condition known as “wetting out”—it’s about as breathable as a garbage bag. If your jacket contains Gore-Tex or some equivalent waterproof barrier, it won’t leak—you’ll just get wet from the inside. Soaked raingear is also heavier and colder. The human body has a difficult time distinguishing between a cold fabric and a wet fabric, which leads many people to believe that their jacket is leaking. This fallacy is reinforced by the fact that condensation increases on the cold fabric, creating visible moisture on the inside.

  Dirt, smoke, and the salt from your sweat all conspire against you. These water-loving particles act like a million little sponges, wicking water into the fabric and overpowering your DWR. Simply washing your garment can revitalize its DWR significantly. Use a mild powdered detergent that leaves no residue behind; a variety of specialized cleaners are available, such as Nikwax Tech Wash or Granger’s G-Wash Cleaner. Hand-washing your gear in the sink or bathtub is the safest bet, though most garments can be machine washed (read the tags carefully). Rinse your gear thoroughly—run a second rinse cycle in your washing machine—to remove any water-loving residue.

HEAT IT UP  Even after the DWR has worn off at the surface, much of it usually remains in the threads below. The trick is to draw it back out and affix it to the surface, a feat accomplished by drying your garment on low heat for a short time (roughly 10-15 minutes) after washing. Do not attempt this at higher temperatures—nylon and polyester melt in the dryer easier than you might think. It’s also possible to accomplish the same thing by ironing your garment on low heat; for safety, place a thin towel or other cotton layer between the iron and your pricey gear.

SEND IN REINFORCEMENTS  If all else fails, a variety of after-market products are available that can help replenish lost DWR powers. Produced by companies like McNett, Gore, Nikwax, and Granger’s, these come in two varieties: wash-in or spray-on. Both should be applied only after the garment has first been cleaned. Wash-in varieties more thoroughly penetrate the fabric, but also coat the inside of your jacket. This can reduce breathability by repelling water that might otherwise escape. Spray-on treatments allow for a more targeted application but must be used in a well-ventilated area and can be messy. Regardless of your revival technique, keep your expectations in check. There’s no question that cleaning, drying, and after-market treatments help revive your rain gear, but the sad truth of the matter is that the DWR will never again be as good as the day you bought it.

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Matt Heid

Equipped blogger Matt Heid is AMC's gear guru: He loves gear and he loves using it in the field. While researching several guidebooks, including AMC's Best Backpacking in New England, he has hiked thousands of miles across New England, California, and Alaska, among other wilderness destinations. He also cycles, climbs, and surfs.