I was recently asked to try and clean a vintage necklace that has beading with 1 inch wire mesh between the beads. The wire mesh has become very dark and has turned green in some areas. She told me it is brass, however the green indicates copper. I am reluctant to clean it because I do not want to ruin the beads or strip the natural patina. I thought of taking a tiny brush with polish to the mesh, but not sure what cleaner or method to use. Do you have some advice for me? She wants to sell this piece in her store.