Bronze will oxidize over time.  Simply use the white polish pad included in your package to restore the beautiful golden lister to your bronze pieces. Another note about bronze; it reacts to the chemistry of your skin. For some it can leave a green mark behind. This is a reaction of the oxidizing of the copper on your skin. Everyone's skin is different, but it is harmless and washes right off.  We are happy to add a thin coating of museum wax to your bronze pieces to slow the oxidation process and prevent it from reacting with your skin. Simply ask us!