Durable Water Repellent (DRW)
DWR stands for Durable Water Repellent. A DWR will help the jacket repel precipitation, so that rain or snow beads up on the outer surface and rolls off. Most waterproof jackets, but not all, are treated with a DWR at the factory. I say most, because some hard shells, like rain slickers, are inherently waterproof; they don’t need a water repellent treatment to fend off precipitation. The DWR is most important for jackets which are both waterproof and breathable, because for even a great material like Gore-Tex, water will eventually get through the first layer, and soak the nylon or polyester. Don’t be mistaken; the fabric is still waterproof, but since the first layer has been penetrated, the breathability of the garment is compromised, and will be reduced. This can make the wearer feel wet inside the jacket, even though the garment is still waterproof. Since the breathability is compromised, the sweat vapor has nothing to do but condense on the inside, leading some to believe that the jacket is leaking. This is known as “wet-out.” Fortunately, the factory where the jacket was DWR-treated is not the only place where water repellency is achieved. There are several companies that manufacture after-market DWR sprays and wash-in treatments, to restore that new-jacket feel.