All jewelry can scratch and wear over time. To keep them looking newer longer, it is best to store your items in individual bags or boxes when your not wearing it. Both silver and bronze jewelry will tarnish less if stored in a ziplock bag free of moisture. It is the exposure to oxygen that makes them oxidize (tarnish).
Each order of a bronze jewellery comes with a polishing cloth. The polishing cloth has two sides. The red side has a polishing compound, use this side first. The yellow side removes the polishing compound, use this side second. Polishing cloths do not come with the purchase of silver or gold items but can be purchased for an extra $8 + tax. Gold doesn't tarnish very much therefore you wont need a polishing cloth. To clean gold you can use dish soap, water and a soft toothbrush.