Though you may want to speed up the patina of an item, if it's a genuine antique, forcing the natural reaction will be ...

It's a rich, natural surface layer that develops over time on vintage and antique ... whereas copper develops a recognizable verdigris, or green, surface patina,' Anthony explains.

These finishes are pre-patinated at the Aurubis mill to create the green/blue/turquoise patina that naturally develops over time with exposure to the environment. The pre-patination process ...

The period of unsightliness can now be eliminated by subjecting the copper to electrolytic corrosion under controlled conditions; after 15 minutes an insoluble patina of good green colour is ...