Homebrew PCBs

Hi all,

I'm trying to make a bubble etching tank that can etch uniformly. I've 
spend lots of my time experimenting with different designs and can't get 
uniform  etching of double sided circuit boards.  I tried large bubbles 
from 2 mm holes  drilled in PVC pipe. They never go evenly on each side 
of the PCB. The bubbles  also have a tendency to group together on one 
side of the tank and circularliquid downward on the opposed side. I also 
tried increasing tank width (from  50 mm to 200 mm) so the solution down 
flow does not interfere rising bubbles. This helped but the bubbles 
still don't flow evenly enough for my liking. I even tried using two 
rows of bubbles on each side of the PCB. All this makes the etching 
terribly non uniform. I was going to look into spray etching but I heard 
spray equipment design must deal with all the same problems. Has anyone 
tried putting stuff like plastic  beads in the solution ? this may even 
up distribution. How about very small bubbles ?

The only other method I've seen is to pump the etchant over the PCB like 
a river  bed.