The zinc surface on the exterior will retain some tiny pinholes only visible under close up inspection, these are a natural result of the molten metal application. .Product Exterior Finish - Mirror Polished ZincThe polished zinc exterior is very simple to clean, just a soft cloth will remove any marks. For more stubborn stains, use Mother polish and a soft fiber cloth. The zinc appearance will change very little throughout the years, darkening only very slightly. To remove marks on the stone resin interior, wipe down with a soft cloth and a dab of liquid soap. Never use any abrasive cleaners on either surface.