Homebrew PCBs

>its the fact you are clearing the copper surface
>from the byproduct produced by the chemical reaction

There has to be relative motion between the copper surface, spent 
etchant and fresh etchant for this to be effective. A spray etcher 
makes this patently obvious. An analogy would be cooling/heating by 
convection means. Your brush, the bubbles and some form of 
pump/nozzle arrangement in the case of the spray etcher would be 
analogous to a fan, moving spent etchant away from the surface and 
at the same time moving fresh(er) etchant in its place.

This movement can be accomplished using self contained fluid 
dynamics by rocking the container, agitation or even possibly 
ultrasonics. A blender would be an example of severe agitation.

Your problem here seems to be that you're hell bent on "selling" 
your method of etching which I've certainly tried and still use for 
developing. It's inconvenient and messy especially if you're using 
the brown stuff. An analogy would probably be the manual versus 
automatic transmission in autos. The AT probably has only one thing 
going for it, ease of use, but that's enough to make it the hands 
down choice for most drivers here in the US. Even with soaring gas 
prices, don't expect to see any change in habits anytime soon.

 --- In Homebrew_PCBs@yahoogroups.com, "Herbert E. Plett" 
<cachureos@...> wrote:
>