Homebrew PCBs

--- In Homebrew_PCBs@yahoogroups.com, "grantfair2001"
<grant.fair@s...> wrote:
> Twenty-five litres? I thought 5 litres would be a life-time supply! I
> haven't adjusted the cupric choride I have in the big picnic cooler
> since I made the solution, and I have made lots of boards in it since,
> but it seems to be slowing, so it's time to check the density and
> titrate to determine acidity level.
> 
> How the heck am I going to use 25 litres, do you imagine?
> 
> Grant

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. 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.

So...HCl works and is cheap, but can be a bit of a pain to use. Of
course there are other neat things you can do with your HCl, including
some interesting metal etching/rusting and wood finishing effects.