I'd use a bright green background.
The bright green will hardly be present as a natural color in the copper, while using and cutting a white background might interfere with highlights. It will be very easy to use any cut out tool or process, like the Select &; Mask feature or even creating masks by using old-school color Channels for selecting.

Use the Decontaminate option in the Select &; Mask process to get rid of any green spills from the background on the object's copper surface.

Oorspronkelijk geplaatst op Quora: What's the best background to take a picture of a copper product against for making the Photoshop cut out tool work best?"