Durable Water Repellent fabrics start life with a surface chemistry that spectacularly repels water. It beads up and rolls off, leaving not a trace of dampness on the material. However, this effect is usually fairly temporary due to a number of factors:
- DWR can be worn off
- DWR can be masked by dirt, detergents and washing powders
- Water can be forced into the weave of the fabric, locking around the DWR fibres
- Condensation can occur within the structure of the fabric, providing a surface that rain can stick to
In short, the fabric can go from water hating (hydrophobic) to water loving (hydrophilic): It has a sentiment change.
FurTech garments utilise this sentiment change because it tends to occur within the woven outer windproof fabric, which then draws moisture off the DWR inner material (this has a fur structure and pushes water outwards). In heavy weather you will see the outer wet out but the inner remains dry as condensation is extracted through the fabrics!
The outer fabric protects the DWR of the inner fabric so that it remains water repellent and the inside remains dry. However, even when saturated (falling into water) the system dries quickly because there is no waterproof membrane to trap the water inside.
Similarly, you may notice the outer fur of aquatic mammals (beavers, otters etc.) saturating, yet the inner fur remains dry!