Homebrew PCBs

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None of us has military decontamination tents in our gardens to do the
etching in if that's what you are asking ;-)

If you are using the low strength H2O2 (3%) the upper limit of
reasonable concentration would be mixing two parts of it straight with
one part 30% HCl. This will give a very strong etchant that'll fume a
little so ventilation during or after etching is advised, but would
not be too crazy. Care must be taken if you user stronger H2O2, then
diluting the HCl first is most definitely called for.

Storing the etchant makes little sense if you only have low
concentration H2O2, it can not be practically used to make CuCl
etchant because it contains too much water to allow the necessary
repeated addition of fresh H2O2.
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So what concentration of H202 do we need if we are interested in making CuCl etchant then?

Thanks,

-- 
Newell