To refinish a porcelain sink, clean the surface thoroughly and sand the sink with wet-dry 400- to 600-grit sandpaper. Apply two coats of epoxy finish paint to the sanded sink, and wipe down with rubbing alcohol once the sink is dry.
Turn off the water source and use an abrasive powder cleaner and scrubbing pad on the porcelain. Set painter's tape and plastic sheeting on the floor.
Detach and remove the pipe just below the drain. Turn the large nut below the sink that connects the metal drain and the metal flange counter clockwise. Using a flat-head screwdriver, peel away the plumber's putty between the drain flange and the sink. Pull the metal drain out and place a bucket beneath the open drain hole to catch any spillage.
Holding a putty knife at a 45-degree angle, scrape away the remaining plumber's putty from the sink. Wearing rubber gloves and goggles, pour a hard-water deposit remover onto the sink and scour with an abrasive pad until all hard-water deposits are eliminated.
Sand the entire surface of the sink. Rinse away the residue and wipe the sink down with a tack cloth.
Wearing an N95 face mask, mix the refinish epoxy into a paint tray with a wooden stick. Coat the sink with the epoxy mixture using a paint roller or an airless sprayer. Let sit for one hour before applying a second coat. Allow the sink to dry for three days before reassembling it and wiping it down with rubbing alcohol.