At 5/3/2022 06:23 UTC Morris Odell wrote:
I do regenerate the solution by bubbling air through it from an aquarium pump but when I'm etching a board the solution gets darker faster than it can regenerate so I give it a little dose of H2O2 which brightens it up instantly. The dark color is due to the Cu(1) reaction product. Once it goes dark I leave the bubbling going overnight and it's as good as new in the morning. Maybe my solution is too dilute but If I use a lot of it it's hard to see how the etch is progressing.
If the solution goes dark due to Cu(1) during etching you either have a solution that is too dilute or you're using an insufficient volume of solution. I'd guess too dilute.
I'm in Australia where "safety" restrictions on chemical sales are inconsistent to put it mildly. You can buy big containers of concentrated HCl from pool shops but at hardware outlets it's kept under lock and key - go figure. You can get all sorts of inflammable solvents, poisonous pesticides and other chemicals from them with no problems. However the laboratory supply stores that were a fun part of my youth have all disappeared.
And the lab supply stores whose customers are commercial labs are reluctant to sell anything remotely dangerous to a home user, or else their prices are too high.
Anyway I might pass on the 35% H2O2 just because it's quite a nasty substance it it encounters something that will decompose it. The potential silver chloride problem is something I didn't know about either and I wouldn't relish having to clean it up. I guess the small bottles of 6% will have to do for my hobby purposes.
The 6% will do just fine, BUT... since it appears that your solution may be too dilute already, maybe you need to stop adding peroxide - which further dilutes it - and instead add some copper wire to it and let it bubble, bubble, bubble, adding some HCl to provide the Cl needed to turn that copper into CuCl2. With a stronger solution, with some excess Cl in the form of HCl, you shouldn't need peroxide.
JimH
