be advized-- the process will release chlorine gas. very bad for yer lungs ! i forgot to mention ferric chloride. works good, re useable, not too xpensive. caswell plating sells the stuff.
When you are patient, you can etch copper with powdered sulfur and olive oil. No, I’m not joking, it works. I got the recipe from a french book. I use it as substitute for liver of sulfur, to blacken silver and copper. If you leave it longer on the surface, it attacks copper. Works best warm, I heat up the piece to 60-80°Celsius.
