I mixed up a batch of HCl and H2O2 and got good etching (which was
mostly from the HCl). There were some bubbles but no chlorine gas. I
etched 6 double sided boards that were on average 20x20 CM in the
first session. The etchant turned the well described emerald green.
3 days later, I went to etch another board and got no (or r-e-a-l-l-y
slow) progress. I bubbled it for about 18 hrs total (with 2 airstones
- lots of bubbles). Still no etching.
I got a hydrometer and the density is 1.075. This is well below the
1.17 recommended by
<
http://users.rcn.com/rexa/Projects/CuCl_ech.html>. From the HCl and
H2O2 I put in, the s.g. should have been 1.029 so I assume that the
difference, 0.046, is from the etched copper in the form of CuCl. It
appears I have too weak a cucl solution by about 1/4 but I'm not 100%
sure about the chemistry here. Everything I've read says that it
doesn't take much copper at all so I'm a bit at a loss here. I need
to get pH measuring capability but the density is clearly wrong.
Any suggestions for fixing? The page mentioned above recommends CuCl
salts which I have no idea where to get and probably shouldn't have to.
I'm going to put a couple pieces of copper in over night to see if I
can get more copper into solution but its not clear to me that will
actually work.