Homebrew PCBs

Chris Hart wrote:
> I don't worry about agitation. I simply leave everything still, and 
> float the board on about a quarter to half inch of echant. The "used" 
> echant is heavier than the fresh, so the etchant naturally keeps the 
> fresher stuff at the surface of the board. The only drawback to this 
> method is it only does one side at a time.
> 

I have tried that method several times , and has never worked well. 
First, I had problems from trapped air bubbles when laying down the PCB 
on the surface. This obviously causes problems. Bubbles can be avoided 
by pre-wetting the copper surface and then carefully releasing the PCB 
on top of the etchant.

The real problem however was when etching if ferric chloride or cupric 
chloride the flow of 'heavy salts' do not fall vertically down 
uniformly. I have consistently observed thin streaks of un-etched copper 
due to some weird behaviour of the flow dynamics in a stagnate etch tank.

Adam