The experimental test of the water resistance of fabrics is an experimental project that textile enterprises need to operate frequently. Because the textile production of different types of fabrics naturally has different requirements and standards for different industries, generally, the standards with higher waterproof requirements for fabrics are mostly tested and tested for fabrics with special waterproof requirements.

General cotton, viscose, silk and hemp are more absorbent than polyester, nylon, polypropylene and other fibers, if they are required to have a high degree of water resistance to make a variety of waterproof appliances, they must be waterproof or water-repellent finishing. Waterproofing actually often includes the meaning of "water repellent". According to the different surface properties of the finished fabric, it can be distinguished, and it can be basically divided into two categories: one is waterproof but breathable finishing. It is evenly coated on the surface of the fabric with a layer of impervious, insoluble in water coating, finishing the pores of the fabric to block water and air through the fabric, this finishing is also called coating finishing (waterproof finishing). Such as polyurethane resin, polypropylene alcohol resin, rubber, tung oil and other treatment, the fabric is not only impermeable and breathable, but also feel hard, so it is not suitable for clothing, generally suitable for industrial cloth or outdoor supplies. The other is waterproof breathable finishing, also known as water repellent finishing. This means that after the fabric is finished, the finishing agent changes the surface properties of the fiber, so that the hydrophilic surface of the fiber becomes hydrophobic, so that the fabric is not easy to be wettable, but it can still breathe and feel soft. It is often used to make raincoats and other clothing fabrics.

The so-called waterproof and permeable (water-repellent) principle is that the water does not wet the fabric under low water pressure, but the sweat distributed by the human body is transmitted through the fabric in the form of water vapor to the outside world, and the water vapor is not condensed between the surface of the human body and the fabric, and the human body does not feel the phenomenon of "boredom" subjectively. After water repellent finishing, the finishing agent changes the surface properties of the fiber, making the surface of the fiber hydrophilic to hydrophobic, the fabric is not easy to be wetted and still breathable, and the feel is soft. Textile washing, fabric scouring and desizing, absorption of dyes and water and oil repellent properties are related to the wettability of liquid to solid. Washing, scouring, desizing and dye absorption processes require high wettability and permeability of fiber materials, while water repellency requires no or little wetting of fiber.