Homebrew PCBs

--- 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