I was curious to hear from others about how often they change out
their ultrasonic solution. Do you change it regularly, when it
turns a certain colour etc?
Ultrasonics work by transferring energy from the transducers to any
surface where the liquid meets solid, and cavitation bubbles can then
scrub that surface. That will include not just your work pieces, but
also the surface of any particles of dirt, gunk, whatever is
suspended in the solution. So when you clean things, and the liquid
gets cloudy with removed stuff like polishing compounds, those
materials in the solution end up diverting energy away from your
work piece. The dirtier the liquid is, the less energy reaches the
surfaces of your work. So the cloudier the liquid is with suspended
gunk, the more you need to clean it in order to maintain full
cleaning efficiency.
Also, because the whole thing works by transmitting vibration al
energy, the same vibrations that cause those cavitation bubbles to
nicely scrub your work piece with the liquid cleaners, can also cause
any suspended materials in the liquid to also be scrubbing your work
piece. Often, those materials, while less efficient at actually
cleaning your work, can be harsher in terms of actually causing
damage to the surfaces. If, for example, you use the ultrasonic to
clean off polishing compounds that are made with harder abrasives,
you may find an increased tenancy for the polish on your work pieces
to be affected by the cleaning action. With softer metals, like cast
silver, you can find this happening just with clean solution too,
just from the energy of the cavitation bubbles abrading the soft
metal (especially where it finds defects, like porosity in the
metal), but when there are abrasive materials in the solution, it
can be more of a problem.
So generally, clean it when it looks like it’s not clear any more.
The color of the liquid isn’t important, but the clarity of it is.
At least, that’s been my experience. Your mileage may vary…
Peter
