Marble is a desirable material for both kitchen and bathroom countertops because it is both attractive and fairly durable. However, many people mistakenly believe that if their cultured marble vanity top become stained, scraped, or scratched, nothing can be done without replacing the vanity surface. In reality, while the process is painstaking, it is quite simple to restore the surface of a cultured marble vanity and make it look new again.
Dampen a piece of 220-grit sandpaper. Beginning at one edge, evenly sand the surface of your cultured marble vanity in long, even lines. Work your way to the opposite edge, maintaining a level sand. Dampen new pieces of sandpaper as needed to continue sanding.
Wipe down your vanity surface with a clean, soft cloth.
Dampen a piece of 400-grit sandpaper and, beginning again at one end, evenly sand the entire cultured marble vanity surface as you did before. Keep the sanding even, level, and straight. Change your damp pieces of sandpaper as required. Wipe your vanity surface again with a clean, soft cloth.
Dampen a piece of 600-grit sandpaper and sand as you did before. When you finish the first sanding, examine your vanity. If all of the mars are removed, stop here and wipe down the vanity thoroughly with a moistened, clean, soft cloth. Continue sanding if your vanity still has scratches or stains. After each sanding, re-examine the surface until it is pristine, then wipe the vanity down completely with the moist cloth.
Dip a paintbrush into the gloss polyurethane varnish and apply an even coat from one end to the other, using long, straight strokes. Allow the polyurethane to dry two to three hours. Apply a second coat if you desire. Let the vanity dry completely overnight.