According to The Real Elliot's instructable titled Stop using Ferric Chloride etchant! (A better etching solution.)
, cupric chloride + hydrochloric acid is an excellent PCB (printed circuit board) etching solution. According to Adam Seychell's Etching with
Air Regenerated Acid Cupric Chloride
, more copper(II) ions enhance etching speed. The purpose of this instructable is to show how to prepare an etching solution with lots of copper(II) ions so that etching can proceed quickly starting with the first board etched.
A solution with copper(II) chloride will be made by electrochemically creating copper powder, oxidizing it into copper(II) oxide, reacting it with hydrochloric acid, and finally converting it into copper(II) chloride with hydrogen peroxide. This is a much faster way of making copper(II) oxide than letting copper metal corrode in hydrochloric acid.