Because the surface of the wool fibers contains a waxy coating, it is water-repellent and spilled substances can be removed before they can penetrate the wool. Even if a stain is not removed immediately, wool will suffer a permanent color damage less quickly than other natural or synthetic substances. Wool also absorbs much less sand or dust from the ground than other fabrics. The best way to get rid of a sand spot e.g. in your Russian wool socks is simply to wipe with a dry brush, because dirt or grid do not easily stick to wool.