Porcelain sinks are beautiful, however, then tend to get stains. If this is your problem, mix 2 tablespoons of cream of tartar with enough lemon juice to make a paste and rub over the marks or discolorations. Let this sit for half an hour. Then Rinse. The lemon juice is a natural bleach and the cream of tartar will have scrubbed away stains and smooth the look of scratches.