Things You'll Need
Use a mild soap and water to clean the dirt from the sign. Rinse away the soap and dry it with a clean, soft cloth.
Remove any rust that has formed where the internal metal plate is exposed. Wear rubber gloves. Wet the rust stain and use the pumice stone to rub the spot in a swirling motion. Pumice stones are volcanic rock that is traditionally used to slough off dead skin from your feet. Rinse the spot under running water to see if the spot is removed. If not, continue to rub the spot. Thoroughly dry the sign once the rust is gone. You can purchase pumice stones at beauty supply stores and at your local grocery store.
Touch up rusted spots. Add a layer of cold enamel to the spots according to package direction. Cold enamel is an adhesive that hardens, usually used in jewelry making and can be found at craft stores and hardware stores.
Polish the sign. Use an ammonia-based glass cleaner and paper towels to finish the restoration.
Leave dents alone. The only way to remove a dent is to hammer it out, which will cause more damage to the sign.