Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

Has anyone tried phosphoric acid for etching? I had some left over
from a old hydroponics project and added about 30% acid with some 3%
Medical hydrogen peroxide from the super store. It etched a small
double-sided board in about 10 mins when warmed in a bath of hot tap
water. It was colorless before the etching and after it was bright
green. There were no fumes or issues as far as I could see and it
looks viable as an enchant. Does anyone have any thoughts??