When brass or copper wire is used to make jewelry that is worn on a part of the body that has a lot of natural oils, such as around the neck, ears or chest, the wire can become coated with corrosion. This corrosion can look unsightly if the wire is used with light colored transparent beads. To keep your jewelry looking clean, choose a high quality metal wire that will resist corrosion, or plan your designs around beads that won't easily show the dark build up. Periodically cleaning the jewelry in a gentle, soapy water solution can help. If your jewelry contains coated beads or natural gemstones that are sensitive to cleaners or scrubbing, test a small area before cleaning the entire piece.