The waterproof rating of a fabric measures its ability to resist liquid penetration. It is typically expressed through a hydrostatic pressure test, which involves applying water pressure to a specific area of the fabric and measuring the pressure at which water begins to seep in. A higher value indicates stronger waterproof performance. Typical waterproof fabrics have a hydrostatic pressure of 1000–3000 mmHg, while high-performance outdoor fabrics can reach 5000 mmHg or even higher.
The washability and abrasion resistance of waterproof fabrics are also important indicators. The ability of a fabric to maintain its waterproof performance after repeated washing or rubbing is key to its practicality. This is usually achieved through immersion, dry rubbing, and washing tests to ensure that coatings or composite materials do not peel off or fail due to daily use.
The waterproof rating of a fabric is also closely related to its moisture permeability balance. Highly waterproof fabrics with poor moisture permeability can make wearers feel stuffy and damp. Therefore, modern waterproof fabrics often incorporate moisture-permeable technologies, such as microporous membranes or functional coatings, allowing water vapor to escape while preventing liquid water penetration. This comprehensive waterproof performance is an important reference indicator for outdoor sports, rain gear, and high-performance clothing.