Copper turning bright cherry red?

I am doing some large sheets of copper for a client. the copper on the first sample sheets turned and nice deep brown with out much work. then I started doing the larger sheets in the same way but a different location and I got a very bright cherry red color. I used vinegar ⇦in bulk on eBay or Amazon [affil link] and salt. Any suggestion? the client wants deep rich brown.

I will bet you a Starbucks that you have a different alloy of copper or a different heat treat copper. There are frequently some differences in the same lot number, let alone different lot numbers, let alone different vendors.

You can use 50 gm potassium permanganate ⇦ on eBay or Amazon [affil link] /5 gm copper sulphate/ 1 lit water solution.Only copper sulphate ⇦ on eBay or Amazon [affil link] solution may be used too(12o gm/1 lit water, solution must be 3 days old)! Good luck!