Copper that is exposed to the elements develops a layer of copper oxide on its surface. Any heat treatment applied to the metal hastens the oxide formation. This oxide is unsightly and makes the copper appear dirty. Copper oxide also interferes with solder and paint or other finishes. If you are working with copper that has become tarnished, you can treat the metal with readily available chemicals to remove the oxidation. Metalworkers refer to the solution and the process as a "pickle," but it is a simple acid wash to clean the copper to bare metal.
Mix sodium bisulfate and water in the plastic pail at the ratio of 0.454kg. of sodium bisulfate to 1 gal. of water. This makes sulphuric acid. Wear eye protection and chemical-resistant gloves and apron, and be careful not to splash any solution on you.
Twist a piece of copper wire onto the copper part as a handle. Immerse the part in the solution and allow it to soak five to 10 minutes or until the metal surface is clean.
Remove the part from the solution. Rinse the part thoroughly in water to remove the acid.
Hang the part by the wire handle to dry.
Sodium bisulfate is available at swimming pool supply stores.
Always wear protective clothing and especially eye protection when working with acid. Avoid breathing the vapours from the acid. Store the acid outdoors with the lid on and out of the reach of children.