I would let the diamonds cool down for a few minutes or more before
quenching them in pickle - that’ll keep them from shattering from
too fast temperature change. I’ve quite shocked that you immediately
pickle your prongs with diamonds after soldering. In all the years I
spent repair ing jewelry in various jewelry stores, we never, ever
immediately quench any jewelry with stones in it after soldering. As
for rubies and sapphires, if they were treated, they could change
color. I do know when I solder with sapphires in place, they change
color as the heat built up, but after a slow cooldown, they returned
to their original color. Another thing to avoid is fluxing the
stones - it dulls them. Since so many rubies are being glass-filled,
I would be extremely cautious and remove them prior to soldering. In
fact, if I have a modern-cut diamond, I ask my clients if it was a
fractured-filled diamond, and if they don’t know, I remove diamond
before soldering. Only on old diamonds (pre 1990), I’ll solder with
them in place.
At the risk of saying something you may already know, I would like
to advise you that boric acid will etch the surface of saphhires
when soldering. It can also etch other corundums, but not as
severely.
I was under the impression that it was using sodium bi-sulphate that
etched a sapphire, not the boric acid. Using ascorbic acid as a
pickle prevents the etching. Is this right?
If you have a few extra dollars (well, more like $5,000+), buy
yourself a pulse arc welder. You can retip a prong holding in a
piece of turquoise! That’s how localized the heat is.
One of my fellow jewelers once blew up a 1 ct. diamond while
trying to tip it with platinum (dummy!)
Just a stray quote… I’ll get to my original impression from the
question in a sec. I’ve soldered on thousands of diamonds for
various reasons, up to about 10 carats. I burned one and only one
stone, from just plain overheating. In my youth. I’ve have triangles
lose their tips when the piece cooled off, from the contraction of
the metal. And now there are filled and drilled stones to be aware
of, yes. But I’ve never had a stone develope cleavages from heat,
which leads to my first impression:
Are you sure it’s a diamond and not a CZ? I mean, sure? A CZ would
act precisely as you describe.
I was under the impression that it was using sodium bi-sulphate
that etched a sapphire, not the boric acid. Using ascorbic acid as
a pickle prevents the etching. Is this right?
...or you aren't sure that the Big 'D" is or isn't loaded with
'feather-filler'... best take it out..
If you’re referring to Yehuda treated diamonds, one can see the
treatment if one knows what to look for. That said, any diamond large
enough to be treated should be removed unless you’re willing to pay
for the stone if it breaks.
Borax is a salt of boric acid. Not the same thing.
At room temperature this is true but at elevated temperatures (575 C
for boric acid and 765 C for borax) they decompose into boron
trioxide (B2O3) which attacks many metal oxides to produce produce
metal metaborates. One of the metal oxides it will dissolve is
aluminum oxide aka corundum, ruby or sapphire.
For some good pictures of what happens when you get borax or boric
acid on a ruby while heating with a torch for repair take a look at
the image on page 6 of this issue of Facette