I find that 9% Peroxide (30 Volume Clear Developer) is a good strength to use. The 27% is too aggressive for me. I can etch a 2X4 inch, 1 ounce board in about 1 minute using 9% H2O2 and a foam paint brush.
Where to buy Peroxide in the US.
Available from Beauty supply shop such as Sally Beauty Supply
10 Volume Clear Developer = 3% Peroxide
20 Volume Clear Developer = 6% Peroxide
30 Volume Clear Developer = 9% Peroxide
40 Volume Clear Developer = 12% Peroxide
BAQUACIL Oxidizer from pool supply store =27% Peroxide
Where to buy Peroxide in the US.
Available from Beauty supply shop such as Sally Beauty Supply
10 Volume Clear Developer = 3% Peroxide
20 Volume Clear Developer = 6% Peroxide
30 Volume Clear Developer = 9% Peroxide
40 Volume Clear Developer = 12% Peroxide
BAQUACIL Oxidizer from pool supply store =27% Peroxide