The components used for etching copper are acetic acid, hydrogen peroxide and sodium chloride. I think the equation may be similar to this:
$$\ce{2H4C2O2 + H2O2 + 2NaCl + Cu -> CuCl2 + 2H3C2O2Na + 2H2O}$$$$\ce{2H3C2O2H + H2O2 + 2NaCl + Cu -> CuCl2 + 2H3C2O2Na + 2H2O}$$
Is this equation correct? There are a lot of bubbles created. What is the gas that is given off?