--- In
Homebrew_PCBs@yahoogroups.com, "Stefan Trethan"
<stefan_trethan@g...> wrote:
>
>
> > Wow really small quantity !!! last question, Can it be regenarate
for
> > ever , or should be dispose after some H2O2 addition ???
> >
> > Thanks
> >
> > Bruno
>
> You can use it indefinitely. Of course HCl is also used up, so you
need to
> add that too after a while. You can either go by feel and add when
it
> doesn't help to add H2O2, or you see any blue sludge on the PCB, or
you
> can look in the links section on how to measure the molarity of HCl
in the
> etchant. Look for the method with the two eyedroppers it is the
only one
> sufficiently simple IMO. You might also want to get a hydrometer.
It is
> used to measure density (amount of copper per volume). You can get
one
> cheap and easy in the car tools store, it is used to measure
battery
> fluid. Should cost well under 10$. Go for the type with the
swimming
> hydrometer in a large glass pipette, not the small plastic
rotating
> pointer one. But that's really only if you are curious about the
etchant,
> it is not a requirement to make it work.
>
> Now if we only keep to add stuff to the etchant it will of course
grow in
> volume. This is very slow and is good because it dilutes the copper
in
> more etchant, otherwise you will reach a point where the specific
gravity
> gets too high. Should you get too much etchant at one point you'll
have to
> dispose of some, but unless you make really many boards regularly
the
> growth is barely noticeable.
>
>
> You will find if you keep using your etchant it will gradually turn
from
> HCl+H2O2 etching to CuCl etching, that means instead of "instantly"
using
> and needing H2O2 to etch the H2O2 can be used to regenerate
existing CuCl
> in the etchant. What that means for you is that once there is
enough CuCl
> you do not necessarily need to add H2O2 each time. You only add it
when
> the etchant turns from a bright green to a darker, brownish color.
If
> there is enough bright green regenerated etchant for the board
there you
> do not need to add any H2O2, even if you last etched months ago.
OTOH it
> will not help to add too much H2O2 - once all the etchant is bright
green
> it does no good and will just decompose to useless oxygen that has
nothing
> to regenerate and is released into the air.
>
>
> ∗∗∗∗∗∗∗∗∗
>
> > If it fizzes, you added too much. It won't actually do any harm
if youdo
> > put too much in. I normally fill the cap of the bottle up and
tipthat
> > in. It seems to be about right for my tank.
> > Les
>
> if it fizzes it creates loads of nasty fumes that are corrosive.
It's
> definitely too much if it does that.
>
> ST
>
Thanks a lot for all these info !!!!, right now mine is bright clear
green but etch really slowly, so i'll get H2O2 30% !!!!
Thanks
Bruno