I have been using Rio’s red-black for achieving a brown/black patina
on copper, with decent results. However, the last two pieces I worked
on had definite, very noticable blue tints. They were acceptable in
the context of the piece, but not something I want to see in the
future. Is there something I am doing to cause this, or is this just
what I should expect in using this product? Also, if anyone has
another commercially-prepared brown patina to recommend, I would
appreciate hearing about it.