The most safest process is to put them in a ultrasonic-cleaner.
Place them in a strainer and let them sit for about 1/2 hour. Do
this after setting, and again after polishing. If no stones fall
out then, for sure you won't be having any problem, trust me on
Agreed, for the most part. But it's possible to have stones slightly
loose, yet not quite loose enough to fall out. To detect those, after
ultrasonic cleaning (which will free any stones with room to move
from whatever position they may have been jammed into, as well as
getting out any dirt or wax that might interfere with seeing
movement, I then take the pieces and hold them against the bench pin,
while holding a hammer hand piece, or for me more often, my air
graver hand piece, adjacent to the jewelry pressed to the bench pin.
The resultant vibration will cause any stones that can move at all,
to visibly dance and jiggle, making them very easy to detect,
especially with good magnification. If they not only stay in through
the trial of the ultrasonic, and then don't show up as dancers and
spinners and other partying stones with vibration,, THEN you know
As well, none of this is a substitute for proper setting technique
and careful inspection. It's possible to have stones set tight,
without falling out, and not moving or vibrating, but still not have
them well set. They may not have enough metal holding them in, or
prongs or beads may not be fully formed or over the stones properly.
In those cases, stones may not fall out now, but may be prone to easy
damage or loosening later, if prongs catch on cloth, or beads too
quickly wear away the little bit holding them if not done properly.
So take the time not only to look for stones that are already loose
or can come out now, but also stones that are not set right, so they
WILL come out too easily during wear.
And then there are the instances, presumably not work you yourself
have set because of course you know better, but jewelry you'll see
where it's beautifully done, stones tight and all, but the overall
design of the jewelry, no matter how well executed is such that it
simply won't give suitable wear and performance before things start
falling apart. I've seen, for example, some so-called "micro pave"
work that I'd trust to hold stones securely for a good long period
of time. But I've also seen such work which, though clearly set with
skill, and stones held well NOW, are so light weight, or the
beads/micro prongs, or whatever, are so exposed by the basic design
of the piece, that you just know they're not going to last long.
Other examples are pieces like channel setting with insufficient
bridges between the two sides of the channel under the stones, such
that any flexing will allow the channel walls to separate a bit,
losing stones. Or settings so light weight that they're easily bent
out of shape, and designed so if that happens, prongs or settings
will be deformed, ensuring stones drop out. Poorly designed things,
no matter how well the (no doubt frustrated) setter does his or her
job, simply may never be secure for the stones...