I pour sea salt (maybe a 1/2 cup) into a small bowl and add vinegar (about 1 to 2 cups).
Mix it around so the salt disolves.
Add copper or bronze pieces to it swish them around....the solution will clean off oils and patinas.
This only takes a few minutes (not more than 5 or so....but longer is ok).
Set up a fuming station: I use a large plastic container with a snap on lid
(I think I got it at Target or Walmart). I made a wire armature that fits inside the container.
This is used to suspend your jewelry over the ammonia.
I put in about 1 cup or more of ammonia into the container with the armature.
While the pieces are wet with salt solution
I drape or hang them from wires and the armature so that they are fumed.
Check the pieces in 10 minutes. You will see some coloration.
If you take it out and let it hang dry the colors will intensify.
If you are not satisfied you can start over...
or maybe spray the salt solution onto the pieces while they are fuming.
Let them dry....I have been spraying them with a Matte Fixative for Charcoal drawing.
Seems to work well.