Your Vapor Pad^® is constructed using an expanded aluminum base, coated with a hydrophilic material that absorbs water.  As warm air from your furnace passes through the Vapor Pad®, the water contained in the coating evaporates to provide your home with humidity. Over time, water deposits build up on the Vapor Pad^®, preventing warm air from passing through. If you wash the Vapor Pad^® in an attempt to remove the deposits, you'll also wash off the hydrophilic coating.  Your humidifier is then unable to provide humidity to your home.