Homebrew PCBs

Hi there,

I've been having problems with my CuCl etching bath (and to a lesser
degree my FeCl etching bath). When I turn the air pump on, the etchant
starts to foam -- if I have the air valve set above a few percent, it'll
foam over the top of the tank in a few minutes.

Acid molarity was around 2.3M last time I checked, with a specific
gravity of around 1.3.

Does anyone know of a way I could reduce the amount of foam being
produced? Reducing airflow only slows down the process, it doesn't stop
it; the foam seems also seems to be quite resistant to being dispersed
and unusually long-lasting. The foam I get when the FeCl tank is being
aerated too quickly usually disperses inside a minute - this stuff takes
a good half hour to revert to a liquid state.

Thanks,
-- 
Phil.
ygroups@...
http://www.philpem.me.uk/