Introduction to breathable water-repellent textiles and their production methods

How DWRs Work

DWRs work by increasing the “contact angle” or “surface tension” created when water contacts a textile. Basically, a high contact angle creates a microscopically “spiky” surface that suspends water droplets on the outer fringe of the fabric.

An optimized DWR keeps droplets in a rounded shape—like a dome-shaped bead. The rounder the droplet, the easier it rolls off the fabric. A low contact angle permits droplets to assume a flattering shape, one that can spread out like a splotch, cling to the fabric’s surface and eventually seep into it.

DWR Ratings

Manufacturers generally measure DWR effectiveness by a spray test. Water is sprayed onto a textile, and the amount that sticks is visually assessed. A score of 90 points indicated that roughly 90% of the fabric has no water sticking to it. The higher the number, the better the performance. The test is then repeated after a number of washings to determine durability.

Test scores and the number of washings is combined to create a rating. For example, a 90/10 rating means the spray test achieved a total of 90 points after 10 washes.

Not all manufacturers publish DWR performance ratings, but here is a basic guide for interpreting any that you find:

• Good: 80 points after 10 washes. This is a basic outerwear finish.
• Excellent: 80 points after 20 washes. Marmot, for example, uses this as its minimum rating for outerwear.
• Superior: 80 points after 50 to 100 washes.