What is DWR?
DWR stands for “durable water repellent,” a thin layer of liquid applied to the outside of technical garments to repel oil, grease, dirt, and water. Garments treated with a DWR treatment will not get saturated with water as easily as garments without, and will be less prone to “wet out,” (when saturated outer fabrics get heavy and cling to your skin making you feel clammy and damp). Naturally, rainwear with a DWR treatment will keep you comfortable and dry more effectively than rainwear without.
Rainwear with highly effective DWR is highly desirable in the outdoor world. Instead of soaking to the core, hikers, backpackers, and campers who wear rainwear with DWR can roll or shake off water and remain dry inside and out. Unfortunately, a DWR treatment is not a permanent property of most outerwear and periodic care is necessary to maintain peak performance.
How does DWR work?
DWR is science at work.
Have you ever seen how many drops of water you can put on a penny in a science class? (Try it if you haven’t, it’s really surprising.) The water stacks up and forms a tall bubble. The tall water droplet has a high contact angle with the penny. When the droplet finally bursts and the water spreads out, the contact angle is very low.
Similarly, an effective DWR treatment keeps water droplets at a high contact angle with the fabric of the rainwear. This minimizes the surface area of the wetted fabric and better allows water droplets to roll off. Less water on the outer fabrics allows the technical waterproof fabric to breathe its best which helps keep you more comfortable. More importantly, keeping dry is a vital component to staying safe on any adventure.
How Long Does DWR Last and How Can I Test My Jacket?
How long a DWR treatment lasts depends mainly on garment use. If you use your garment several times each week for intense periods of activity, the DWR will not last as long as a jacket that is used, say, only a few times per month. And DWR applied at the factory to a new garment typically lasts longer than reapplications.
To test your jacket’s DWR, sprinkle on some water. If the water beads up, your DWR is in good shape. If the water soaks in and obvious darker areas appear, it is time to restore your DWR. Be sure to test your jacket all over, as soaking can occur from any breach.