Hi Kara In case you wanted another opinion to help assure you that
it’s OK to heat your diamond… You’ll be fine heating the diamond,
even if you’re soldering directly below it. Use a good coating of
boric acid and alcohol to protect your stone and your metal. As
mentioned before, LET IT AIR COOL, never quench a diamond or any
stone for that matter until you can handle it with your bare
fingers.
If you get into heating diamonds, or other stones that can take
heat, always heat slowly. Don’t shock the stone by raising its
temperature dramatically, the bigger the stone the more important
this is. You’ll be fine with a 40 pointer, especially since you’re
not working on the stone itself.
You may have to give your ring a good pickling before you perform
this repair, since some of that water may have washed out your flux
and caused oxidation during your first attempt. A little time in
the ultrasonic wouldn’t hurt either. Assuming your rings are
partially tacked together. If they’re completely apart just clean
’em good and get a nice shiny surface where you want your solder to
flow.
I think what I would do would be to take a strip of 18k solder and
roll it as thin as I could (and then roll it again to make sure it’s
damn good and flat). Cut your chips off of this strip and wedge
them between the platinum band and the 18K band. I would flux prior
to this to help the wedging process and to help assure that the flux
gets forced between your two bands. Flux again. I use prips flux
for most repair jobs with gold.
Keep in mind that the solder will flow towards the hottest spot. I
would make sure the solder flowed well onto the 18k band first, and
then heat the platinum band to get a good bond.
You’ll be just fine, let us know how the whole thing goes.