Durable water repellent, or DWR, is a coating added to fabrics at the factory to make them water-resistant (hydrophobic). Most factory-applied treatments are fluoropolymer based; these applications are quite thin and not always effective. Durable water repellents are commonly used in conjunction with waterproof breathable fabrics such as Gore-Tex to prevent the outer layer of fabric from becoming saturated with water. This saturation, called 'wetting out,' can reduce the garment's breathability (moisture transport through the breathable membrane) and let water through. As the DWR wears off over time, re-treatment is recommended when necessary. Many spray-on and wash-in products for treatment of non-waterproof garments and re-treatment of proofed garments losing their water-repellency are available.
Methods for factory application of DWR treatments involve applying a solution of a chemical onto the surface of the fabric by spraying or dipping, or chemical vapor deposition (CVD). The advantages of CVD include reducing the use of environmentally harmful solvents; requiring less DWR; and an extremely thin waterproof layer that has less effect on the natural look and feel of the fabric.
