In some areas car-washes have found that no matter what detergents they use a slight grey film still remains on the car. When we analyse this it normally consists of heavy metals such as cadmium and lead. These have come from car exhausts and other atmospheric pollutants and are now stuck onto the paint by their electrons. This dirt is simply removed with a wipe, but the electron bond will be too strong for detergents to remove. So in a touch free car wash the simplest way to remove this soiling is with a mild acid wash being applied over the vehicle. The phosphoric acid blend not being as objectionable to people or equipment as other acid products.