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Mysterious exploding prongs


#1

Hi all,

Had a weirdness at the shop yesterday and I’m hoping perhaps
someone might be able to help me figure out what happened.

A customer brought in a 3 diamond engagement ring bought at one
of our stores. The configuration is:

1.25 ctr set in 6prong low-base die struck head/14K white (2) .50
side stones set in 4prong low-base (die-struck looking)
heads/14K white Plain 14K yellow shank

Almost as basic as they come. The problem is, two prongs
detached from one of the side stones, next to the center. The
breaks are at near equal level, about half a millimeter upward
from the “scoop” between the prongs. Looking at the break with a
loupe, you can see the kind of crystalization in the metal that
usually comes from stress or a bad casting.

Now I could understand if it was the outside prongs or if the
inner ones showed any sign of the metal being pulled in or
outward, but nothing indicates bending at all. They seem to have
just detached explosively… blew themselves right off, losing a
half-carat stone in the process. The rest of the mounting does
not show stress, denting or bending from customer abuse.

What might cause this to happen? I find it odd also that it was
2 prongs at once.

Thanks in advance for any ideas you might have to share. I’m in
expectation of finding out I’ve overlooked the obvious :wink:

Jane


#2

Hi Jane

What a bummer! Have you considered that the gold may have been
exposed to chlorine, either in bleach or chlorinated pool water?
This can leach the alloys out over time and lead to brittleness
in the gold. If this is the case there may be more weakened
prongs in the ring. Test them by bending them a little, you can’t
necessarily see this kind of erosion by merely looking at the
ring. I’ve had a 14kt ring shank that weas exposed to chlorine
crumble in my fingers as I was sizing it. Other than that, the
prongs could have been overheated during soldering, leading to
breakage.

Best of luck, Tom Tietze, The Artisan Workshop


#3

Jane:

You did’nt specify as to wheather you made the piece or if you
had anything to do with it perviously. I’ll presume you did’nt
and on that basis I would suggest that eather the head was
defective and the prongs simply broke off(a fine hair-line crack)
or they had been repaired by trimming off the old prongs to the
same level and soldering (badly) new prongs on and resetting the
stone. I’d ask the customer where they purchased the piece and
if they or someone else had previously repaired it. Even if it
had only been in for something else previously, it’s possible
that an inexperienced bench person messed up and tried to repair
it without the customer’s knoweledge. Hope this helps;

Steve (once inexperienced myself)


#4

Assuming the prongs are white gold, perhaps they were not cooled
enough after any soldering work was done when the ring was made.
If you quench white gold (or any gold) when hot ,there is some
"crystalization" . Brittleness is the result. Just my .02. Rob
RIngold


#5

Dear Jane, I have seen prongs broken on the inside of the
setting, most of the time it seemed to be caused by a chemical
reaction with the alloys in the 14k prongs. Chorine is the
biggest culprit I can think of. Had one customer that had soaked
her rings over night to clean and almost all of the prongs broke
in this fashion. hope this helps,

Janine in Redding Ca.


#6

well Jane , did you notice if the other 2 prongs on the same
setting hav e been bent towards the broken prongs-- showing that
the ring was dropped or otherwise damaged this way? At any rate,
this is one of the woes of nicke l- white gold settings.; prong
breakage. This process can be greatly sped up when chlorine
comes into contact with the nickel in white gold-- was your
customer taking jacuzzi’s with her ring on; or cleaning her ring
in bleach?

Hope that this might help, Peter Slone


#7

Jane, While I cannot be sure with out seeing the ring in
question I think that this sounds like chemically induced stress
corrosion, and yes I would consider this a form of costumer
abuse. The problem is that in nickel white gold alloys chlorine
and bromine will attack the gold alloy, inducing stress cracks
along the grain boundaries of the alloy. Sound like a bad
casting? Nickel is not particularly soluble as a gold nickel
solid solution, thus as the metal solidifies the nickel is
concentrated along the grain boundaries of the resultant alloy.
Hoover & Strong http://hooverandstrong.com have a page on this
problem in there ASK TORRY section. This type of failure can be
induced rather quickly with household cleaning products,
especially those which contain bleach as a principal ingredient.

Remember, contrary to the adds, Beach does not clean, Bleach
destroys. This destruction may be what you want in the case of
bacteria, but not what you want for gold.

WayneM


#8

Hi Jane,

This is probably a brittleness problem common to white gold.
Usually caused by the original jeweler quenching the heads when
hot, a definite no no, or exposure to chlorides, etc… The real
root of the problem is that the nickel used as a whitening agent
in white gold is insoluble with gold. It will mix with the copper
and the zinc, but not with the gold. You are then left with
nickel rich boundaries that are very susceptible to cracking.
People who swim a lot may find that their prongs are cracking
off, people who have their hands in bleach water have this
trouble too. The problem is that nothing whitens gold like
nickel. Some use palladium but it is softer and appears more
yellow. The best thing you can do is replace the heads with new
ones whenever you see this, and don’t quench them. If a heads
shows this problem it will likely occur on other prongs. If you
find that the customer is a swimmer or is particularly upset you
should set them in platinum. I have a shop that does work for
many stores and we use 95% platinum heads. We have no trouble
with prongs cracking or shearing off. Hoover and Strong has a
better explanation of this cracking phenomena in their catalog.
Anyway I am very sympathetic to your plight, we are all in the
same sinking ship.

Mark P.
WI


#9

Pretty hard to tell, exactly, without a microscopic examination
of the break. But here are some possiblities:

Chlorine, as in swimming pools, bleach, etc, can attack white
golds. Would tend to find any microscopic flaws, and induce
brittleness wherever it could penatrate a bit. That can happen
anywhere. More of a problem with castings, but die struck heads
are not immune. Contamination with mercury, such as from a
broken thermometer, could do the same.

Is it possible this is a casting, made from a model using die
struck heads, and then just cleaned up really well? If so,
interior sections of the casting might tend to cool slower in the
casting process, which would induce larger crystal size. And the
last sections to solidify are sometimes starved for metal due to
shrinkage in the adjacent areas pulling metal out of any still
molten areas.

Over annealing, as in getting the metal too hot, too long, in
assembling the heads, can cause an increase in crystal size, and
brittleness. Also, white golds tend to be brittle when hot, so
if you solder together a piece and then quench it while it’s
still too hot, you can crack the metal. An interior section of
the ring might have remained a little hotter, a little longer,
in soldering the heads on, and if the ring were then quenched
while those prongs were still too hot, tiny cracks could have
started. However, this requires the gold to still be slightly
glowing red hot, or at least close to it, before it’s a likely
problem. That usually requires a pretty impatient goldsmith to
quench it that quickly on this sort of open, light weight design.

contamination with metals like lead, in assembly of the
mounting. Such low melting metals can penatrate the white gold,
leaving the metal weak. And some white gold solders can also be
somewhat brittle, so if this is near where some assembly too
place, and such solders were used, then improper assembly could
be the culprit.

Maybe you just have a bad head. heads are nice clean looking
stampings, sure. But they’re made from sheet metal, and that has
to come from somewhere. It’s not common, but a flaw in that
sheet metal, like a small bubble, might be undetected, yet lead
to a head with the starts of a crack. The fact that two prongs
simultaneously broke would fit this scenario, since a larger
flaw in the sheet could easily bridge two or more prongs in the
stamping. For the record, though, this is pretty rare. Usually,
bad sheet metal leads to stampings that fail before the stamping
process is complete.

It’s also possible that improper setting/tightening techniques
are at fault, though this seems less likely with inside prongs.
If the prongs were repeatedly bent back and for, just a little,
they might not show marks, yet could have been weakened.

Hope this helps.

Peter Rowe


#10

We’ve 5 stores and it was made somewhere in the company as far
as I know. Hard to recall every piece you’ve made over 12 years
in one place, but I’m fair certain this isn’t one of mine :wink: Nor
can I detect any evidence of a previous repair to the prongs. The
spontaneous break of a defective piece was my guess, but it
seemed odd that it was the two inner prongs simultaneously. Going
to look further into the possibility of problems due to pool
chlorination or cleaning in bleach as some folks have suggested.

thanks,
Jane


#11

Hi Jane, sounds like a batch of metal with a “bad patch” - like
an inclusion in a diamond. I’ve had the occasional piece of metal
that had an inbuilt flaw. The last experience I had was with some
platinum plate. The metal company replaced it immediately, bless
’em.

I also had an experience with die-struck findings peeling apart
on the claws. Again, clearly faulty metal and the supplier
replaced them.

It’s bad luck that the flaw happened to show up on your claws.
Still, I’m only guessing in a half-educated way. I’m sure there
will be lots of better conjecture from our colleagues.

Kind regards, Rex from Oz.


#12

This is why everyone is moving away from nickle white gold.
Nickle white gold is known to have this problem. It will
spontaneously shear off once in awhile. Start using palladium
white gold (available through Hoover and Strong) or platinum.


#13

Jane, It sounds like stress corrosion. Nickle alloyed white gold
is very susceptible to stress corrosion (especially if the prongs
were quenched after soldering or if the ring was put in
chlorine). I have seen rings crumble into a zillion peices after
being exposed to bleach or hair dyes. I always try to talk the
customer into a platinum or palladium alloy head to avoid this
problem. Stuller has a very good article on stress corrosion in
the back of their metals catalog. Good Luck Ken Sanders