So far I've not tried too much variation on the patina I use for copper, but I read (re-read, really - I've had the book for a long time) about adding a blue patina in the book The Jeweler's Guide to Decorative Finishes with ammonia and decided to give it a try.
I prepped some copper components by sanding them lightly, then put them in a big plastic container and sprinkled salt on them.
Ammonia fumes are what do the trick, so I put a little dish of ammonia in the bigger container and then put a lid on the whole thing.
It took three tries to get a shade I was really happy with - the first couple of times I left the copper in the container with the ammonia for a couple of days and the blue became so dark it was closer to black so I tumbled the pieces and started over.
...and the finished earrings. The finish is rough and very organic but I like it! (Final pictures were taken outside.)
