For hard water stains, mold, mildew, etc.: apply InstaGone by spraying or brushing. These types of surfaces usually have a film of soap scum not visible to the eye. We recommend taking a scouring pad or a fine grade stainless steel wool pad to the stained area, scrubbing in a circular motion. This allows the soap scum to be lifted and for Instagone to penetrate through and remove the actual stains. Once you scrub the area, spray Instagone as you normally would. Allow for several applications depending on the severity of the stain. Once finished, rinse off.