[sdiy] Etching PCBs with non-toxic chemicals

[David G. Dixon]

> You can add excess scrap aluminium to give non-toxic 
> aluminium chloride and metallic copper. if my memory of chem 
> classes 50 years ago is right..

Yes.  We call this "cementation".  Scrap iron works as well, and is the
basis of the industrial cementation process which was used to recover copper
from dilute ore dump runoff solutions.  Indeed, this is probably the first
"hydrometallurgical" process, as it was first applied at the original Rio
Tinto mine in Spain in the 1500s.