Homebrew PCBs

we discussed this a while back, how it might be done, today i stumbled  
across that:

When Hydrogen Peroxide  and Hydrochloric Acid (HCl) are used to replenish  
the Cupric Chloride () etchant, the Hydrogen Peroxide  additions are  
controlled by an Oxidation/Reduction Potential (ORP) meter, which  
functions very similarly to a pH meter. The Hydrochloric Acid additions  
are controlled by a very sensitive conductivity meter, which has only  
recently been commercially available.

here:

<http://www.pcbfab.com/iepart3.html>

I still think automatic maintainance is pointless in our low volume  
applications, but i wanted to have it mentioned as we did discuss it at  
some point and that text provides hints.


ST