I personally like the antique patina look of my copper jewelry. But maybe you don't! So here is the solution (pun intended) on how to maintain the shiny look of your copper jewelry even if it has already obtained that antique look. This will only work if your copper jewelry was made with bare (non-coated) copper wire.
Here is the solution. In a glass bowl, mix together 1/2 teaspoon of regular table salt and 1/2 cup of either white vinegar or lemon juice. Frankly white vinegar is cheaper! Stir until the salt has dissolved and then heat it in the microwave for about a minute. Drop your copper jewelry in the solution and allow it to sit for anywhere from 10 to 20 minutes, checking it after the first 10 minutes. Rinse your piece of jewelry in cool water and pat dry.
That's it! You can store the salt and vinegar/lemon juice solution in the refrigerator for several months.
Note: If your jewelry contains selenite, do not use this method. Selenite will begin to dissolve in any liquid.
This is the same solution that I use when I am creating copper ball head pins using a torch. It removes any of the fire scale that occurs during the torching process.