Cleaning pearls isn’t too tricky, The most destructive thing is ammonia, it will forever kill the nacre and leave a dull, mat finish.
I use an ultra sonic cleaner called “Dalco Red”.
There are others, I think Rio has a version of this as well. I get mine from Gamzon in NY.
Pearls can go into an ultrasonic with no issues, either cultured or natural. However simulates with a applied surface are risky, it’s easy to break the surface bond between the painted surface and the underlying bead.
No toothpaste, it’s too abrasive, however a tooth brush and soft-soap will also do the job.
The first pearl was not drilled, the second was. In either case I use “Gorilla” super glue, or if it’s an old pearl thats over drilled (too big a hole) I’ll use 2 part, 5 min. epoxy.
I make sure the hole is a near snug fit to the post, then force a bit of glue down the hole and wipe a bit on the post.
It sticks . I make my own posts in platinum keeping the as drawn texture. I’ve yet to have one come loose (55 years and counting…)
Watch, tomorrow morning someone will call with a loose pearl…
Pearls are surprisingly tough, soft to be sure, but I see far less damage than one would expect.
I’m working with one now that is carbon dated (university of Arizona & GIA) at (between) 300 BC to 900 AD, It has amazing luster. I’ll post photos when the piece is ready.