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What stones can handle heat?


#1

Hi all,

I’ve been working as a manufacturing goldsmith for various companies
in the U.K for the last 7 years. Recently i moved and the only work
oppertunities i could find was setting up as a self employed
goldsmith and repair worker. Currently the majority of my work is
repairs and in some ways i feel out of my depth! I am currently
dealing with allot of clusters and retipping claws. Cold you tell me
what stones it is safe to heat? Obviously Diamond and Saphires are
ok. But how about Rubies Emeralds Amethysts and Garnets? The majority
of the jobs ive been removing the stones before retipping claws,
purely because im unsure what stones are safe to heat and what arent.
This makes jobs slower and in many ways more risky in breaking
stones. Also with larger Diamonds is it advised to remove the stone
instead of heating just incase of accidental heat damage? I can think
of nothing worse than damaging a customers ring due to my lack of
knowledge, and even though im insured i would prefer not to have to
fork out for a new stone!

Thanks for your time,
Jon


#2

You’re going to hear a lot of people give you the red, white and blue
rule that it’s okay to heat rubies, diamonds and sapphires but unless
it’s absolutely unavoidable I don’t believe any stones should be
heated today. There are far too many treatments out there now and you
just simply don’t know how heating a stone is going to impact it.
Diamonds are fracture filled, rubies have glass, dye or who knows
what else in them and the same with sapphires. It just isn’t safe
anymore.

Daniel R. Spirer, G.G.
Daniel R. Spirer Jewelers, LLC
www.spirerjewelers.com


#3

In the last 25 yrs. of doing repairs and manufacturing work for the
jewelry industry, I have found that a good rule of thumb is, Heat
only RED WHITE AND BLUE. Ruby Diamond and Saph. You are usually safe
with that, otherwise, remove and reset the stones.


#4

The stones that will take heat are diamond, sapphire, ruby and
synthetics like CZ and spinels [also naturals] Garnets will stand
the heat but beware of the rate of rise in temperature, same with
zircons. Everything else is best removed, but even sapphires and
rubies can change colour with heat so beware.

Nick


#5

It comes down to risk assessment. You take risk as soon as you
accept an item from a customer and it gets worse from there.

Large diamonds are not usually a problem if you get them super
clean. You do have to watch out for filling and questionable
inclusions. Be careful about frosting. If it happens you can have it
repolished but time and money is needed to correct.

with larger Diamonds is it advised to remove the stone instead of
heating 

If you yank it, replace the setting. You’ve already noticed that
resetting a retipped prong is a pain. Its because the solder is
harder than the parent alloy and takes more force with the setting
pliers, increasing the prospect of a chipped girdle. Funny how the
retip just gives way suddenly, letting the jaws come crashing down
onto the stone.(Oh, and really scrutinize for adequate girdle
thickness). If you do have to reuse the original setting, I’d advise
replacing the entire prong rather than just the tip. If you chip a
two pointer no big deal, chip a carat and you will ruin your
afternoon.

Small diamonds are easier to overheat. Figure that you will destroy
a few now and then and build it into your pricing. The hurdle with
melees is to really clean under the stone, lye works when other
methods fail.

Corundums can be retipped if you do not get flux on the stone. After
you pick up the solder on the poker, dip the tip in flux and heat a
little til it fluffs white, then clear, then apply to prong. Any
large or valuable corundum, the risk is not worth the gamble…time
for a new head or setting. But with new stone treatments coming at us
all the time, its wisest not to heat at all.

Pretty much everything else is problematic. Sometimes garnets will
retip, CZs. Emeralds never. If you don’t want to buy a new stone, do
not heat it.

even though im insured i would prefer not to have to fork out for a
new stone! 

You might seek a clarification from your insurer. Damage incurred
during work was not traditionally covered. But I admit I may be out
of date on that one.

When you’re a jobber you’re expected do what the client requests.
But there are times when you should object and get a waiver in
advance. Retailers sometimes do not know beans. I think overall,
you’re better off to replace components than to retip. If you’re
dealing direct with the public you can give your advice re inherent
risk and consequence, offer at least two ways to do the job, disavow
liability if they choose to proceed against your best advice. Get
paid either way. If they insist you try the cheap way first, it
should be their gamble, not yours.

I have retipped many thousand of prongs, once in a while I lost a
$tone. I have reset many many old stones in new mountings, can’t
recall losing anything this way. Risk assessment. Why would you
willingly take higher risk for lower pay? As much as you can, try to
work under your terms, not those imposed on you.

Good luck and ain’t repair fun!


#6
Obviously Diamond and Saphires are ok. But how about Rubies
Emeralds Amethysts and Garnets? 

Jon - ruby sapphire diamond only. I’ve seen people solder on some
garnets but I won’t. Make sure that diamond is coated with boric
acid/methanol, make sure corundum is NOT or you can and will get
boric acid etching, which requires repolishing to remove.

As for larger stones, that’s somewhat up to you. I don’t solder on
larger corundum mostly because I’m worried about treatment of all
kinds. I don’t solder on fancy colored diamonds for the same reason -
if the heat alters the color there’s no turning back. A gemologist
might say it can’t happen, but it’s not worth the risk. I’ve soldered
on ten carat diamonds before…

Oh, yeah - corundum but not stars - also you never know what any
silky stone (like a Kashmir) is going to do. Plus you’d be nuts to
take a torch to a Kashmir of any caliber.

http://www.donivanandmaggiora.com


#7

Add to this list “Faceted” ruby & Sapphire. Cab stones have air
bubbles too many times and will explode. For safety sake, I would
only consider the colors of the American Flag

Diamond, ruby sapphire.

David Geller


#8
ruby sapphire diamond only. I've seen people solder on some garnets
but I won't. Make sure that diamond is coated with boric
acid/methanol, make sure corundum is NOT or you can and will get
boric acid etching, which requires repolishing to remove. 

So for corundum, it’s not advisable to put ANY coating on prior to
heating? Just clean the stone prior and heat gently, right?


#9
ruby sapphire diamond only. I've seen people solder on some
garnets but I won't. 

There are caveats to heating those stones too. Diamonds that have
been “enhanced” by means of laser drilling and filling with glass
should not be heated. It won’t destroy the diamond, but the glass
filling can ooze out or at least discolor. I hesitate to heat any
diamond that is heavily included too. And there’s a certain kind of
glass filled ruby that you can’t heat either. p Corundum cabachons
shouldn’t be heated because they have much less integrity to the
crystal structure and will often split or pieces will flake off. Now
for saphires. Most saphires have been heated before cutting to even
out the color banding that is often present. But natural blues that
have never been heated can contain “negative crystals” filled with
water. These will often split if heated with a torch. How you
recognize these situations is another long story for another post.

So for corundum, it's not advisable to put ANY coating on prior to
heating? Just clean the stone prior and heat gently, right? 

Yest and no. A little boric acid on the stone won’t do much as long
as you don’t get the stone that hot, like glowing red. But in bright
light, it’s not always obvious how hot a stone is getting. The paste
type fluxes have a much more dramatic effect and should not be
present on the stones surface when you heat it, say, for re-tipping.
Even so, it depends on the stone. As for garnets, 2 or 3 millimeter
stones seem to survive pretty well, but bigger than that it’s about
50/50 odds they’ll fracture internally.

By the way, most synthetic stones, like the ones in mothers rings,
can take torch heat, except the green ones. They’re usually composite
stones (and don’t put the older green ones in the pickle or you’ll
see the glue seam around the girdle when you take them out).
Nowadays, the white stones in mo’s rings are usually CZ’s, and
they’ll take heat if you bring them up very slowly and let them cool
slowly, but it takes practice.

There are other stones that can be heated, but my rule of thumb is
this: If I either don’t want to spend the money to replace it, or
it’s going to be difficult to get a new stone back in the setting,
I’d refrain from heating it.

David L. Huffman


#10
So for corundum, it's not advisable to put ANY coating on prior to
heating? Just clean the stone prior and heat gently, right? 

That’s right. No flux or boric acid. In fact, try to use a neutral
flame, not a strongly reducing (soft) one, as well. The idea is that
corundum is a metallic oxide. Fluxes dissolve oxides, etching the
stone. Reducing flames can also reduce the oxide to the metal,
causing a loss of polish and a sort of irridescence on the surface.
Not that common, but possible. Easier to remove, though, if it
happens (platinum rouge will take that off. But the polish of the
stone is still affected.) With both effects, the higher the
temperature you heat the stone too, the greater the risk of damage.
That’s true for diamonds as well. One other warning with corundum…
Even with these precautions, some stones will be damaged. If the
stones are oiled to improve apparent clarity (common with ruby
melee), the oil can burn leaving you with a blackened stone hard or
impossible to clean up. Some sapphires will fade or change color when
heated. And either type, if not heat treated already (often means a
rather high quality gem), can sometimes contain fluid filled
inclusions. If those stones are heated, the water in the inclusion
forms steam and pressure that can break the stone. The bottom line
with corrundum is to examine the stone very carefully before hand,
and if you are not sure it’s safe, or if you cannot afford to replace
it if damaged, or broken, then the wiser choice would be to unset it
for the repair work, just like more sensative stones would have to
be.

Peter


#11

I was told diamonds as long as they don’t have big flaws… and
rubies and sapphires, but not to quench them after soldering as that
can cause fracturing…When it comes to casting in place, I think
most people use synthetic corrundums, cz, diamonds etc.

jeanne
jeannius.com


#12

Oops!

In my previous post, I stated that there were some situations where
you shouldn’t heat a diamond. I forgot one…

NEVER heat an irradiated blue diamond. And for all purposed,
consider all of the blue ones irradiated. A natural blue diamond is a
rare creature indeed, and priced accordingly. But heat one of the
irradiated ones… well, it won’t be blue when you’re finished.

David L. Huffman


#13
So for corundum, it's not advisable to put ANY coating on prior to
heating? Just clean the stone prior and heat gently, right? 

Yes, Drew that’s it exactly. I’ve read all the replies to your post,
and it all sounded good to me, BTW. Mostly to remember that there’s
still no guarantees, you just need to tilt the odds in your favor
with skill and experience.

Diamond is carbon, which will burn in oxygen. It can take the heat
if the surface is protected from oxygen - boric acid has a higher
melting and burn-off temp than borax does, which is why we use it as
a dip. Corundum is aluminum oxide, which won’t burn because it’s
already burned - that’s why it’s “oxide” ;<}

That’s obviously not to deny that anything can “burn” - be subjected
to excessive heat. But no, corundum doesn’t require a coating. Boric
acid etching of corundum was featured and analyzed long ago in Gems
and Gemology - like 20 years ago or something, if anyone cares to
look for it. The surface of the stone gets a texture like mud-cracks
or the pattern of a turtle shell, with slightly raised lines. It’s
not boric acid that pickle will remove, it actually etches the
surface of the stone and must be polished to remove. The good news
is that it IS only surface, and polishing will remove it.

http://www.donivanandmaggiora.com