Add the ingredients in a large pot over medium high heat. Bring to a boil. Wipe any dirt or grime off of the copper piece.
Place the tarnished copper in the boiling water with tongs. As the copper oxide is removed, turn the piece to a new spot. You can also ladle the water bath over the piece for hard to reach areas. If needed, use a soft toothbrush to get into crevices to remove grime.
Once all the tarnish is removed, make sure to clean the copper piece thoroughly with warm water. Vinegar and salt can speed up the collection of tarnish.
How to Prevent Copper from Tarnishing
You can apply a lacquer coating that will seal out water and oxygen. Make sure to do several even, thin coats so it is completely coated well. This won't work on items exposed to heat like pots and pans or copper sinks.
You can apply a thin coat of oil to slow the process. Some commonly used oils for preventing tarnish are linseed oil, baby oil, mineral oil, and beeswax. A high quality car wax can also be applied for items that are strictly for display. If you are coating something that you handle often use to cook or store food, be sure to use an oil that is safe for consumption.