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Yep, with fresh peroxide in warm water it takes less than 20 mins for small pcb's. No dangerous HCl needed. The chemistry behind is Cu+ H3Cit +H2O2→ H[CuCit] +2H2O
Peroxide from pharmacy and baker's citric acid powder works like a charm for me. 100 ml 3% H2O2 + 30g citric acid + 5g NaCl (salt), mix thoroughly, don't drink. And surely make use of it while it's fresh and warm.