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Soldering close to diamonds

I am turning a diamond earring into a small ladies ring adding 18K
yellow gold to the existing setting of 14 diamonds set in 18K white
gold. One edge is only 2mm from 4 square diamonds set in a square.
Therefore I will trim the other side to match. I know to cover the
diamonds well with a heat shield product but I wonder if I am taking
too great a risk with this little space to work before the diamonds.
The easy 18k yellow solder I have melts at 100 degrees lower than the
temperature diamonds burn. As I have never attempted this before I
would like to hear from more experienced goldsmiths. Thanks, Nance

I know to cover the diamonds well with a heat shield product but I
wonder if I am taking too great a risk with this little space to
work before the diamonds 

Nance, that sounds like you may be making an important mistake. You
don’t need to protect the diamonds with a heat shield product. Heat
is not the enemy.

Oxygen is. You need to protect the diamonds from the atmosphere
during heating.

If you simply coat the diamonds with one of the heat protecting
materials sold for insulating, you may have problems. They don’t
always work. And if the diamonds get hot while covered in that junk,
they’ll contact the atmosphere, and if too hot, can burn, causing the
surfaces to get frosty white (requires having the diamond repolished.
Not something you do yourself). Instead, first make sure the diamonds
are very very clean. No trace of oils or dirt or polishing compounds
or other junk. Nice clean diamonds. Then dip the whole piece in a
mix of denatured alcohol and boric acid powder (you can get small
amounts of boric acid powder just at the drug store, often sold as an
eye wash.) You need powdered form, not granules. The boric acid only
slightly dissolves, but the alcohol is a carrier, not a solvent here.
Mix it so it’s a light mix about like milk. Dip the work, and ignite,
burning off the alcohol. It will leave a light white coating on the
diamonds. As you then heat the work, this will glaze over, coating
the diamonds with a boric acid glaze that protects them from
oxidation during heating. You want to also try to see that the
diamonds never get so hot that they’re actually glowing. In practice,
this amounts to keeping the diamonds below around 1000F, though with
practice, you can get a lot hotter, though I don’t recommend that.
After soldering, air cool till you can touch it. Never quench the
work if it has diamonds or other gems. Then pickle to remove the
boric acid glaze.

If your work has other gems, most of them are more sensative to heat
(ruby and sapphire are exceptions, but even then, not always. If
flawed, or oiled, they are not safe to heat). Most of these do indeed
need the heat sink insulating products. But for diamonds, those
products make the job harder, and are less safe for the stones.


Doing repair work I often have to solder prongs and channels
directly on orunder diamonds. It can be done, BUT everything must be
very clean.

Any oil or dirt will burns onto the diamonds, creating a nightmare.
No such thing as too clean at this point! Sonic, steam, examine.
Maybe clean again.

After cleaning we apply boric acid and alcohol, to create a barrier
between the hot diamond and gases. Then we solder and air cool the
piece of jewelry. NO quenching!

Hello Nance, You can solder on top of a diamond if you wish. You can
use any kind of gold or silver solder but not platinum solder. Do
not, however, quench the piece; just let it cool slowly. Have fun.

You can solder right next to diamonds. Do it deliberate and quick.
Don’t linger and cause the diamonds to be red hot. I tip on diamonds
all the time. Fire coat Flux, have the joint ready and solder it. No

Thank you all for your fast responses and help. I will have the
diamonds be very clean and use that barrier as described. Thank you
for the encouragement.