Homebrew PCBs

Umm.. you can buy Copper Chloride powder and mix it with water+HCl.
It's a lot easier and you can obtain a more accurate concentration right away. 
http://www.techfreakz.org/cucl2/?slide=2

~Rolan

--- In Homebrew_PCBs@yahoogroups.com, Adam Seychell 
> 
> 
> I'm still not sure on the best way to prepare the etchant. Weigh 
> some scrap copper wire for about 150 g/l final etch solution.
> Place in yor ready to go etching tank and pour in some 10% HCl so 
> the copper is half immersed. Leave it for a few days, You'll see 
> the copper form thick coating of  blue copper hydroxide on bits 
> exposed to air. The liquid will go dark brown and the copper 
> immersed will be reddish and partially etched. Add more 
> concentrated HCl (30% to 37% wt) and dissolve the blue copper 
> hydroxide. Keep adding some HCl every day, the solution should be 
> very dark brown.
> After about 3 ~4 days, and the copper is fully immersed with acid 
> then turn on the air sparger. The idea is to etch the remaining 
> copper. Its a bit tricky to know when to add more acid and/or 
> water, I guess you can do a copper(I) chloride test as I 
> described in my previous post. If very high copper(I) is evident 
> after 10 hours of sparging then it means there is low acid. The 
> bubbling may take 1 or 2 days to dissolve all the copper. You 
> don't want too high of acid during the preparation. If you can't 
> do titrations and keep the HCl below 3.7%,  then there are other 
> signs to look for, such as irritating HCl fuming from the 
> sparger, or if too low, there will be excessive copper(I), or 
> even signs of copper hydroxide precipitate on the surface of the 
> solution, when the HCl has reached to zero.
> When all the copper is dissolved then you need to add the 
> necessary water and HCl to bring up the desired volume.
> Check with hydrometer for sp.gr about 1.26 ~ 1.29