> The stuff you get from a hardware store is muriatic acid, about 31%
> HCl concentration. It's not the nastiest chemical ever, but it's about
> the nastiest you can easily find for sale. Should be treated with
> respect. Use it outside or with lots of ventilation, away from any
> metals you don't want rusted or dulled by the vapors. You don't really
> dilute it that much to etch PCBs, but it is pretty cheap. When you add
> the H2O2, it'll start outgassing.
If there is any gassing you have WAY too much H2O2 and probably also too
much HCl
concentration.
> Don't breathe that stuff, it'll chew
> up your lungs and throat. Always add the acid to water, not the other
> way around. Keep a bucket of water and an open box of baking soda
> nearby to dilute and neutralize any accidents. Don't ever put aluminum
> into the etchant mixture, it violently outgasses hydrogen and produces
> a lot of heat: bad combination for something happening in a tank of
> corrosive acid. You also don't want to leave mixed etchant sitting
> around, it'll degrade pretty quickly.
Only the H2O2 will outgass oxygen.
You should only add "just enough" oxygen to keep the etchant regenerated.
You can store it forever, but excess H2O2 is lost. So simply do not add
any excess.
Once you have enough copper in it you don't need to add H2O2 each time.
I have my tank filled with 1 liter and i only add H2O2 each second etch,
with
weeks in between (That means it works without H2O2 once enough CuCl is in
there,
you only need the H2O2 to free the Cl from HCl. The Cl combines with Cu to
make
two CuCl out of one Cu2Cl (or some such thing i don't understand)).
I have never dumped the Tank contents, it is good for years, but keeps
growing.
>
> So...HCl works and is cheap, but can be a bit of a pain to use.
HCl and H2O2 "until it bubbles like hell" is a pain to use.
Properly used CuCl etchant regenerated wih H2O2 is very convenient.
Much bettter than all other etchants, IMO, because it's cheap and you
never need to exchange it.
Read in the links section, CuCl, how to use it properly.
The recepies will suggest adding CuCl powder, forget about that and
simply start with "clean" HCl and H2O2, and water, and gradually bring the
copper up by etching boards. You need to add H2O2 each time until there is
enough
CuCl solved.
ST