If you collect old copper as an investment or you are a dealer planning to sell the item, you should never polish, and only clean if absolutely necessary. Polishing a piece of copper with original patina – what non-collectors often think of as tarnish – will destroy its value.

How do you polish antique copper?

"If you have a large copper item and you want to clean it quickly, you can boil three cups of water, add a cup of vinegar and one tablespoon or more of salt," says Reichert. Next, you would stir until the salt is dissolved and then place the copper item in the water. "The tarnish will come right off."

Should Antiques be polished?

Sometimes the beauty of an antique brass object is its tarnish, in which case Sorenson recommends leaving it alone. “Oftentimes it's best to forgo the polishing process altogether,” he says, noting that polishing antiques could significantly reduce their value.