Or you could attach a pager motor to the outside of the etching tank.
http://www.pagermotors.com/index_files/English/Parts.htmEd Okerson
> In article ,
> Peter Johansson wrote:
> > Here's a thought on agitation: Find a gear motor that runs somewhere
> > arround 30 RPM. Mount a disc perhaps 2-3 inches in diameter with an
> > offset center to the motor. Mount underneath one edge of the tray.
> > Might something like this do the trick?
>
> How about sitting the tray on the cone edges of an old loudspeaker - say
> about an 8". With a tone generator and an amplifier you could
> experiment
> with different frequencies to see which produced the desired effect -
> ultrasonic?
>
>
>
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