Enamel paint is commonly used on copper because it produces a tough bond between the metal and paint, which reduces chipping or peeling. However, this strong bond also makes enamel paints very hard to remove. Difficult does not mean impossible, however: Enamel paint can be removed in several ways.
Sandblasting can be used to remove enamel paint from copper. However, this method is not usually recommended because the sand particles can also leave scratches and nick the surface of the delicate metal. Sandblasting can be followed with sanding to remove any scratches or nicks. This method should only be used for thick copper pieces. If the copper is thin, no amount of sanding will remove the nicks from sandblasting without ruining the piece.
Scraping is another method that can be attempted to remove enamel paint from copper. The scraping method works best if used in conjunction with another method, such as paint thinner or boiling. Use a metal scouring pad or wire brush to scrape the paint off of the surface of the copper. This will make a terrible sound, but the sound is reduced if done underwater. The water also may encourage the enamel paint to scrape away.
Acetone is a solvent that easily eats away enamel paint. If you choose to use this method, test the solvent on a hidden area of the copper first. The acetone may damage the shine or color of the copper. Since acetone evaporates so quickly, it can be hard for it to stay on the surface of the copper long enough to eat away the paint. This problem can be solved by placing the copper piece in a large plastic bag. If your copper piece is too large to fit in a bag you can use plastic wrap to cover the copper while it's still wet. Allow the acetone to sit for 10 to 20 minutes. The paint should be easy to wipe away after this time.
Lacquer thinner is another excellent enamel paint remover. While commonly used to remove paint from wood, it is almost equally effective at removing paint from copper. Use the same plastic trick as with the acetone. Allow the paint thinner to sit for 20 to 30 minutes, then wipe away. Stubborn paint can be scraped away with a metal pad or wire brush.
Sometimes heating the paint and copper will release the bond that the enamel paint has on the surface of the copper. Boil the piece for 10 minutes in water then remove it and allow it to cool. The paint should chip away. Some of the paint may come loose during the boiling process as well. Do not use this procedure in a pot used for eating.