Wiper blades not only keep rain water off a car's windshield, they also help provide a clear viewing area for the driver. Therefore, keeping your wiper blades working and in top shape is important. Hardening of the blade's rubber, however, can reduce their effectiveness. This hardening occurs naturally over time as the blades are exposed to sun and other elements. If the rubber on your wiper blades has hardened, a few things will help restore their usefulness.