including the messy old standby etchant ferric chloride, or even [Sebastian]’s preferred sodium persulfate method. Being out of that etchant, he decided to give the acid-peroxide method a go and ...

He’s come up with a way of creating PCBs with any 3D printer and steel rod ... is using the traditional method of etching away copper, just some ferric chloride and a bit of time.

ferric chloride, 2 ml. concentrated hydrochloric acid and 99 ml. methyl alcohol) etching for 20–60 min ... made upon a carburized plain carbon steel, upon a carburized ‘Westinghouse Puron ...