I have attempted to make this board below at home. Applied negative photoresist paint, left to dry for about 4 hours each side over a radiator, applied a double layer tracing paper with the artwork on each side (4 sheets of tracing paper total), exposed it outside for 25 minutes for each side (cloudy winter day in Europe), developed with washing soda + water, etched with an unknown ratio solution of HCl + H2O2.
At first the solution was 2 : 1 of HCl 37% : H2O2 3%. I have etched a PCB in it fine, loosely put a lid on its opaque container and let it sit for a week. Then I have attempted to reuse the same solution about one week later but it would not etch. Poured some H2O2, nothing, poured some HCl, still would not etch, then poured a bit more H2O2 and it did its thing, but slower than the original solution.
In the picture below the is missing copper and some of the copper is a bit stained.
In this second photo the far side looks OK, but the near side has lots of missing traces (towards the middle of the board).
Any clues on what might need changing ?