Bathtubs have come a long way since the availability of running water -- from cast iron and clawfoot tubs to porcelain and fiberglass. Some porcelain tubs have fiberglass walls, and some of the new fiberglass tubs are one piece with sides and walls. New products on the market make cleaning and repairs to bathtubs easier for the do-it-yourself homeowner. Use products such as sandpaper according to directions or you can damage the finish on your porcelain bathtub.
Make certain that your bathtub is porcelain before attempting a repair recommended for porcelain. Porcelain is baked-on enamel over a metal base. It feels like fine china. When you knock on it with your knuckles, it sounds and feels solid. Fiberglass feels less solid and sounds lighter weight. Fiberglass is warmer to the touch. Check the sides as well as the tub if you plan to work on any areas other than the tub itself.
Cleaning and Alternatives
Attempt cleaning and repair of minor damage to a porcelain bathtub with products on the market. A melamine cleaning product might clean your bathtub so you don't need to use sandpaper. Products containing oxalic acid remove rust from porcelain. Try these products first before using sandpaper. Acrylic liners are an alternative to sanding available for all styles of bathtubs. A factory-trained installer fits the liner over the tub to make your old porcelain tub look new.
Sandpaper is an abrasive product that makes minor scratches on the porcelain surface. Use the finest grit available that does the job. Sandpaper with 1500 to 2000 grit used with a light touch does less damage than coarser sandpapers, but the wet-or-dry silicon carbide 3000-grit sandpaper might be all you need to clean or diminish the appearance of minor blemishes. Wet the sandpaper and rub in a small circular motion with a light touch for the least damage to the porcelain. Beware of a black stain on a porcelain tub. If the porcelain on your tub wears thin, it shows the black metal through the porcelain. When you sand the porcelain, you could rub more porcelain off and make the discoloration worse.
Products are available to repair the porcelain finish on a bathtub. These products are enamels or paints, not porcelain, because porcelain requires a high firing temperature. Porcelain touch-up kits are available in different colors. Find the color closest to your tub color, but err on the lighter side because darker colors make the repair obvious. Attempt to match the color by locating a kit from the same manufacturer. Your likelihood of satisfaction and success of the repair is in using the correct color for the repair. If there is a sealer recommended for the repair, use the sealer to prevent the repair from peeling in hot water.