In the magical world of this newsgroup called rec.crafts.jewelry on
Sun, 28 Sep 2008 19:06:09 -0700 we were all amazed to see "Triple"
write:

Does anyone have any experience with ultrasonic jewelry cleaners that just
use tap water? I'd love to be good the environment and not use chemicals if
I can. But I don't want to buy something that doesn't work and end up
tossing into a landfill. Any advice would be appreciated.

I used to use ammonia, a naturally occurring gas, in my ultra, but
customers bitched that it stank.
One day I ran out and, having nothing else, used some ZEP industrial
strength floor stripper.
It worked so unbelievably well I bought a whole gallon of it and now
use it exclusively.
BTW, I took a sacrificial pearl and soaked it in the undiluted ZEP for
a month. No change. And I steamed it afterwards and no nacre flew off.