When I first started up my home workshop (this century, not last
), I did make up some concentrated copper sulphate solution and put a few drops of battery acid into the mix. (100mL of solution or thereabouts).
One side effect is that clean steel does get a nice copper coat which prevents rusting…
I only ever use permanent spirit markers (Pentel, Sharpie…) now as it's just cleaner and simpler. There is also a choice of colours too-
Steve