Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

Brian Lalor <blalor@...> writes:

> > Don't dispose of them! The acid/peroxide etchant becomes CuCl etchant
> > with use, which can be air regenerated and used over and over again.
>
> What if you really really need to? :-) Baking soda?

IIRC you add a base (sodium hydroxide (drain cleaner) if you have it,
else baking soda) until the copper precipitates. That tells you the
pH has just passed neutral. Let the water evaporate, leaving a copper
salt "brick" at the bottom. Bring that to a hazmat place.