I've been using the electrolytic process for my organic and
porous stone set jewelry for several years now and find it works
fine - just drop the temperature when you're doing such stones. I
regularly successfully clean silver with malachite, amber, coral,
etc., but don't leave them in long and treat my stones back and
front with glycerine or mineral oil when the pieces are dry.
I'm working in sterling but have never noticed an interaction
with my solder or any discoloration.
In your position, I would try a piece of fine silver of lesser
importance before committing to this process for .999; although
my bezel surrounds, both plain and gallery, are built with .999,
and they always come out looking great.
Incidentally, if anyone's interested - to build Gold Filled
bezels, I've found that if I use 14kt bezel strip on Gold Filled
sheet with 14kt solder it doesn't boost the price too much and
lends itself to bright-cutting and polishing and comes out
looking right. I solder all my Gold Filled using 14kt easy solder
(one temperature solder as you don't want to get the piece too
hot) and have produced some fairly ambitious pieces. The idea is
to keep the piece simple and try to design with the least number
of solder joins in mind. Stay away from that single clad stuff.
Nina - Silver Design, 9122 S. Federal Hwy, Suite 249,
Pt. St. Lucie, FL. 34952 : Toll Free:1-888-460-1800
: Email: @Nina