I used and avow that method. One thing I would like to know, though, is if it's essentially the same method as the "cupric chloride" one. I'm guessing if you re

I used and avow that method. One thing I would like to know, though, is if it's essentially the same method as the "cupric chloride" one. I'm guessing if you reuse the previous etching solution and add fresh HCl and H2O2 (which I did) one should get both etching reactions. In any case it works very well, and it is safe, something which commenters in another hackaday article some time ago were doubting.