Homebrew PCBs

Hi,

I'm thinking about building a spray etcher. This has been discussed 
here before, but I haven't found an answer to my questions. I want 
to build the centrifugal type so that no pump is needed. Can anyone 
tell me how exactly these pick up the fluid at the bottom? Probably 
a picture? And the other thing I need to know is what speed is 
needed to spin the tube fast enough to spread the fluid.

Regards
Martin