I've had mixed results using Tarnex with copper. Often the metal comes out shiny and  new, but other times it comes out looking nice and then in a few hours looks horrendous - like old dingy dark brass. Does this mean the brass ones were not really copper? am I asking for trouble to dip copper plated items into Tarnex?

Do you wash them off real good after dipping?

I've had the same problems with the tarnex and copper.  At first I thought it was going to be great.  My copper chainmaille was beautiful after a quick dip in the Tarnex...but after using it a few times...my copper is now dull and almost a matt finish.  My tumbler won't even shine the copper up.  I'm thinking that the tarnex must do some permanant damage to the copper.  When I wear copper, it turns dark on my skin before the day is out.  I thought tarnex was the answer, but I guess not.  I'm now using the vinegar and salt.

 Try using lemon water!

 thanks guys, I guess I won't use it anymore - darn! but I still love it for silver.