Darkening Solution for chemically darkening light spots that may appear in the bottom of copper sinks. Small eyedropper bottle with enough solution to use for a lifetime on your sink. For use on small areas of change only. Copper Sinks are a living finish and do change with use. They will darken back down on their own with use and the natural oxidation that occurs. If you feel you can't wait for the natural change, this is a quick fix. We recommend our Sink Wax to protect the sink from such changes. Item number WAX04. Instructions for use provided on the bottle.