Homebrew PCBs

i also use hcl and h2o2.
the h2o2 is too cheap to bother with heating etc.

but be aware that strong bubbling is a sign of too much h2o2, then it is 
too fast and may
attack weak resists.

i judge it by color.
if it is light green you are right with the concentration. it will work.
you can only see some very small bubbles and the board will take some 
minutes.

if it turns from light green to dark green/brown (when shaking the 
container gently normally)
you need some more h2o2, with 35% stuff and a small board only a few drops 
are needed.


the problem:

after using the etchant the amount of h2o2 still in the solution causes it 
to get light green.
when you fill it in a bottle and use it next time it is still light green.
but the speedup from the h2o2 is not there (it has disintegrated in the 
meantime).
so you can either wait a longer time (until it gets dark green from normal 
cucl etching) and add h2o2 then
or you can add a SMALL amount of h2o2 at the beginning.


i beg you not to make it "cooking". as the bubbles break up they spill a 
lot of etchant around.
place some white paper over you will see.
also a lot of (clorine?) gas is produced, endangering your health.

further more h2o2 is simply used up (it is lost because it disappeares).


get yourself some 35% h2o2 at a chemicals shop. (maybe good drugstores have 
it - here they have).
it is very cheap and you need MUCH less...

regards
stefan