Customers often ask about polishing their antique & vintage metals. My general advice is that (unlike wooden pieces where value can be greatly affected by altering an original surface) metals can be certainly polished. With regard to copper and brass, polish to your taste but I personally prefer hand-polishing. People do use polishing wheels but my feeling is that this kind of aggressive polishing can give your antique brass and copper a finish that is so bright the character of the piece can be lost (until Mother Nature takes over and everything darkens up again). As far as silver & silver plate, hand-polishing is essential. The depth of the design in silver & silver plate comes from the tarnish that is left in the grooves of the scrollwork–when you remove all of the tarnish, you lose the beauty of the detail.
So what are best polishes? My favorites are in the grocery store. If you have water available, try Bartender’s Friend for copper & brass and Wright’s Silver Polish for silver & silver plate. If you are in your antiques shop 24-7 (without a kitchen sink available), try one of my favorites, Nevr-Dull. The polish is in the cotton wadding so it’s soft, it’s easy, and it works on a wide variety of metals without water. Just buff your metals clean with the wadding and wipe with a dry paper towel or cotton rag.