For tougher cleanup jobs:

• Linda Cobb (the Queen of Clean) suggests mixing 3 parts cream of tartar with 1 part hydrogen peroxide and then using a damp cloth, massage the mix into the sink. Let it dry then wipe with a damp cloth.
• 1 part vinegar, 1 part hot water, 1/2 part baking soda. Scrub mixture into sink using a damp sponge or cloth. Rinse well then dry with a clean cloth.
• Spray a layer of hot water over the sink to cover, then spray a layer of household ammonia. Cover sink with a plastic bag (stretched across the top with ends taped down on counter top) and leave overnight. Rinse the ammonia off in the morning then wash with hot, soapy water and dry with a clean cloth.