Cars, like people, suffer in polluted environments and it is not unusual for surfaces on your vehicle to become rough under hand even though these maybe microscopic. The vehicle loses its smoothness and clarity on what may otherwise be a freshly cleaned car. Unfortunately there is not a lot that we can do to avoid these main contaminants and they can become firmly bonded to the paint surface and then begin the process of corrosion and expansion, which distorts and damages the paint film. It cannot be removed by simple snow foam and shampoo washing. In-fact washing could increase damage further if you are using the incorrect tools.