Homebrew PCBs

hi

bubbler is working fine already.
Aginst better knoweledge i decided to try cutting corners and did not test  
the bubbler with water.
I just took a plastic hose, made 5 holes with a hot needle, put a isolated  
copper wire (seal the ends)
in the hose. Also selaled one end of the hose. the wire inside allows for  
shaping and holds it down and in place.

The bubbles are maybe 6mm dia. and all holes work equally well.
The bubbles create a mad circular current, up in the center and down the  
sides. Also along with the
big bubbles there are thousands of tiny bubbles, which you only see after  
stopping the pump, when
they rise slowly to the surface.

The mixing is of course homogenous, i am sure 1/10 of the bubbles or less  
would already ensure complete
mixing.

when the bubbles rise they spread, so that at the top of the tank they  
already cover the whole area,
but on the bottom they do etch streaks where they rise. i think about  
adding two more holes
to create a more even etch. Also it could be that some obstruction above  
the air holes might
help to spread the bubbles over the entire length, i was thinking about a  
roll of plastic fly screen,
what do you think?

i had to modify the pump to get a suction input, but it wasn't much of a  
problem.
the closed circuit seems to work from what i can tell, but long-term  
rusting will show the truth..

So, at the end of the day it seems bubbling is really a good method to mix  
the etchant.

Thanks for the suggestion of a hot needle to punch the holes.

ST