Add approximately one cup of salt to a warm bath and let it dilute for a few minutes. Soak in the bath for at least 20 minutes to get the maximum benefit of the bath. If you are purchasing the BLACK edition please bear in mind that the activated charcoal has the possibility to stick to any kind of residual soap or dirt in your bathtub. This will appear like it has stained your tub, but after a thorough cleaning it will go away.