[sdiy] Etching PCBs with non-toxic chemicals

[David G. Dixon]

> So , I basically add little pieces (sraps) of aluminum and 
> let it sit there for a few days ? Do I still have a piece of 
> metal in there after days? Or is it completely dissolved ?
> And could the liquid afterwards theoretically dumped in my 
> septic tank ? Or is it gonna cause other problems further 
> down in the septic system ? Like killing all the fermentation ? 

Aluminum foil would work well.  It will react electrochemically with both
the copper and the protons in solution.  Hence, in addition to copper
cement, you will also make hydrogen gas.  You're better off just
neutralizing the solution with soda ash and dumping the residue in the
garbage, or just washing it down the sink.  There's nothing particularly
toxic about cupric hydroxide.  They feed it to cattle.  You may even make a
bit of basic copper carbonate, which is a pretty green stone which is used
in jewelry (malachite).  In the tiny quantities you'll generate from etching
the odd PCB, you'd put more copper in the sewer by losing a penny down a
storm drain!