Homebrew PCBs

Hi Guys,

I am working on a new etching tank for Ferric Chloride.  I was using 
two bubble stones for aquariums, one clogged pretty quickly and the 
second one didn't last all that long.

So, I figured I would take a sheet of PCB board and drill a bunch of 
holes in it as a baffle.  The I would run an air hose through it and I 
would have lot's of tiny bubbles coming up.  Nope, I got big bubbles 
out of a couple of the holes.  I started out with .020" diameter 
holes, then tried .035, then .045" and finally .055" holes. Not 
working good at all.

So, I am stumped now and am wondering what you guys are using to get 
better distribution of your air bubbles.

Chris