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Soldering with heat-treated sapphires


#1

I recently made a pair of 22k earrings with heat treated
sapphires which I bezel set. Now I want to remove the posts and
solder wires instead. Can I do this without removing the stones?
Will the fact that they were heat treated change the color of
the sapphires? Thanks for any or suggestions.

Yumi :open_mouth:


#2

Yumi:

NO! I would simply remove them. I assume these are rather
valuable saphires and this is being done at the customer’s
request. Simply pass on the cost.

Best;
Steve


#3

Hello Yumi, Pull the stones. When I got into this business, one
usually heated a sapphire during a repair without a worry.
Nowadays, they usually shatter. I suppose this is because most
are treated. I’ve given up heating them. Tom Arnold


#4

@rexsmerten

Hi Yumi, I’ve soldered around Australian heat-treated sapphires
and had no problems. One of my colleagues who has been
researching and experimenting with various combinations of heat
and fluxes here in Australia even suggested that heating may
actually improve some of these treated sapphires. I haven’t seen
any dramatic improvements as a result of my soldering, but then
again, I haven’t had any problems either.

It’s most important not to let any flux burn onto the sapphire
as you heat - it will etch into the sapphire’s surface. The usual
precautions apply: work clean and no sudden temperature changes.
Hope this helps. Rex from Oz


#5

Yumi-san: The heat treatment that Sapphires are subjected to is
much greater than the heat your soldering torch will emit. I have
had only one loss due to soldering upon a sapphire and that was
due to coating the gem with Batton’s flux, instead of the usual
boric acid coating i use to prevent fire scale. The hardened
flux, during several reheatings, expanded and contracted upon the
gems surface and abraded it. The only other precaution you
should observe, as with any other is the danger caused
by thermal shock. Keep your soldering station away from drafts or
cold surfaces and let the soldered items cool down before putting
them into the pickle. Finally, the only other precaution i can
think of is to be concerned with the nature of any inclusions or
fractures within a gemstone and if the gem’s setting would affect
it through heat expansion.

Gambattay. Kim Eric Lilot.


#6

This past week a goldsmith who has retipped many sapphires in
the past retipped a sapphire in place and burned the surface of
the stone and is now having to get it repolished.


#7

@rexsmerten

Hi Tom, I’ve always enjoyed and valued your posts. Your comment
about the rising incidence of shattering sapphires has made me
aware that I am perhaps becoming too casual and careless in my
old age.

(Hey Yumi, I take back what I said in my last post. Tom’s advice
is better.)

I haven’t had the personal experience of having a treated
sapphire shatter, so I’ve blithely continued to do what I’ve
always done - solder 'em in settings. I’ll make some enquiries of
my colleagues here in Australia where there’s lots of sapphires
and (whether we like it or not) lots of heat-treated or "cooked"
sapph.


#8

Hi all - I just wanted to thank everyone who replied to my
question regarding soldering w/heat treated sapphires. I really
appreciate the time and effort it took to reply. Orchid is the
greatest resource for those of us without much experience or
training (and I’m sure all of you seasoned vets out there learn
something new once in a while too). Thanks again!!

yumi :slight_smile:


#9

Hi Yumi, Some of us might like to think we’re “seasoned vets”,
but we’ve probably just had more time to make mistakes if truth
be told. Kind regards, Rex from Oz


#10

Hello yumi,

Just thought I’d share a story, A customer of a very exclusive
local jeweller had her ruby ring repaired and she was concerned
over the seemingly dull lustre her ruby now had following this
repair. Fearing, in the best 20/20 manner that her stone had been
switched she took the ring to her appraiser/gemmologist who
showed her the stone under magnification revealing the thin skin
of borax glass that had been fused to the surface of the stone,
dulling its appearance. When she was advised that this was
caused by sloppy workmanship that allowed flux to contact the
stone when the piece was heated she vowed never to patronise that
jeweller again and intended to tell as many people as possible
the same thing. The jeweller never had the opportunity to correct
their fault, they just lost prospective business. I repolished
the stone.


#11

Personaly, I would never heat a ruby of any size to begin with.
The only stone that’s safe to heat, aside for synthetics (and
you’re not always safe there) is a natural diamond and only after
a through coating of boric acid/denatured alcohol. Having said
this, I guess I must be stingy with my flux because I’ve never
had a flux burn on a stone that I know of in nearly 20 years.

Respectably submitted;
Steve


#12

What this story proves is what many of us on the list keep
saying: No one should be heating any stones other than diamonds
(and only those diamonds that you are sure are not fracture
filled) when repairing jewelry. All stones should be removed
from the piece unless they can be adequately protected.


#13

Kathy I can’t argue with that at all BUT…in most retail
environments many challenges occur daily…listen to this…good
customer came in other day …she has spent many, many thousands
with me…she had a cheap 10K cluster type amethyst ring missing
a prong, she found the stone …going to give it to her young
daughter to lose most probably so fix it cheap Mr.
Parresol…mmmmmmmm in a low growl in my mind… so if I take the
stones out all the prongs will probably break so now what…You
know Kathy what ones needs is a good water torch, bought mine
used 15 years ago, and a good GRS microscope also purchased 15
years ago…so I cleaned the ring, boric acid/alcohol fluxed the
thing, clamped it in an old pair of tweezers, cut a small piece
of gold wire proper size for the prong, cut a small chip of
solder ( put the solder on the wire first { I am breaking rules
anyway} ) cranked up the microscope to about 15 power put a
small tip on the water torch and touched the fluxed flame to the
ring where the prong has to go…applied the prong with a pair of
my watch tweezers (ouch) and presto in less than 2 seconds done
and no heat around any stones…none the worse for wear…pickled
in 99% citric acid powder thanks for the tip Charles …

I am willing to surmise that many Orchidians have equipment like
mine but just don’t say anything…I rarely use my two gas
torches, a little torch and a meco torch…

No you shoudn’t heat stones. You need speed…sounds like a
movie…Now If I could just figure a way to get more done.

Terry Parresol
Horologist
Goldsmith


#14

Hi Terry, Due to a computer malfunction some of my orchid
responses went out under my wife’s name. Her only connnection to
the jewelry business is that she gets to wear all of my
creations. It is my belief that if a ring 's prongs are all
going to break due to a removal of the stones then they should
all be worked on. You do the customer a disservice if you allow
her to walk out with a piece that is going to break again soon
anyway. I don’t believe most jewelers have the kind of torch
you mention here. Many of them are limited to using the more
traditional oxy propane, oxy acet, acet or natual gas and air
combinations. But I am sure all the Orchid members would be
happy to respond to an informal survey if you asked them.
Daniel


#15
    Terry Hi there, What is the 99% citric acid - what is it
for and where do you find it? 

Hello Peter S., First I have to credit Charles Lewton-Brain for
the idea but I cannot remember where l read it.

I had a local lab distill pure citric acid powder… .99 pure…
and it works very well as a pickle for gold ( and silver) is not
in any way toxic and is organic blah blah blahh anyway I have
worked it for many months using various concentrations and hot
and cold to find out from an everyday work environment if this
stuff works…seems to me it does with no worries as to what I
throw in the pot and what else might be in there. I do not know
where to tell you to get this stuff as I couldn’t find any pure
stuff…I am having a fair amount made up right now, but my get
rich quick scheme will probably not work. A pointer here if any
of you secure some for trial…don’t leave gold sitting in heated
solution for a very loong time ( say three hours ) as it dulled
the metal…easy to clean but another step ( this was a very
concentrated heated solution { 4 water to 1powder }

Cordially,

Terry Parresol


#16
     You do the customer a disservice if  you allow her to walk
out with a piece that is going to break again soon anyway.  I
don't believe most jewelers have the kind of torch you mention
here. Many of them are limited to using the more traditional
oxy propane, oxy acet, acet or natual gas and air combinations.
 But I am sure all the Orchid members would be happy to respond
to an informal survey if you asked them. 

Dear Daniel, I actually agree with you but in this instance my
customer knew exactly what was going on and the nature of the
repair…a long term retail environment is interesting to say
the least…on equipment I am not sure if it is the torch (
although I can coax a flame out of a #30 tip, as much as it is
the power of the GRS microscope…after many years this is the
single most important piece of equipment I have ever bought.
Peter Slone, I think it was him, posted a note on how much he
enjoys his new 4x high grade optics…try bead setting 50 small
diamonds under a grs microscope cranked up to 10 power or 20 if
you like and see how quick you can get this done…or for you
watchmakers stud a hairspring, only took me a minute…this used
to take an hour of trial and error under a 10 power loupe. I am
not really a tool ‘freak’ as I have really a small amount of
tools…it is just the ones I picked years ago were carefully
thought out because I didn’t have a lot of money then…anyway I
do well with it. On the employee theft issue, it appears that
many of us have a similar “problem”. A recently made 2 carat
diamond pave heart with clip in white gold for omega or chain
wear ended up attached to a 24 karat gold 3 ounce chain
recently purchased in Indonesia on a beautiful blonde, who, when
questioned about said merchandise merely said "Oh, I must have
had a blonde moment " as she smiled and walked away. Sigh. Do
you get your jewelry back Daniel?

Terry Parresol


#17

Terry I seemed to have missed something here. Did someone else
bring up employee theft because I didn’t although I am always
willing to talk about the topic (although thank God in 17 years
of retailing we have never had an employee theft). I don’t think
you are a tool freak either; I just don’t think a lot of the
Orchid list members have some of these tools, especially not the
beginners.


#18

I have tipped the prongs many time without stone removal,
perhaps you need the redi prongs their easy to work with … John
the Ringman


#19

It has been my experience that one of the main problems with
soldering on heat treated sapphires is the reaction between the
oxygen in the torch flame, boric acid, and occasionally with
coloring agents if stones were diffused. After having to
repolished a few stones on the top side only I decided to coat a
stone with boric acid/alcohol then sprinkle powdered charcoal on
top. I heat everything until the glass forms then allow it to
cool a little so I can scrape the charcoal off the top of the
prongs then flux and retip. The charcoal creates a reducing
atmosphere on top of the stone and also slows down the cooling
process. It has been my experience that if a stone breaks from
being heated the fracture usually occurs during the cooling
process. I have had jewelers tell me that they just stopped
using firecoat and flux, but this creates the problem of
excessive firescale inside the settings.

Blaine Lewis
New Approach School for Jewelers


#20

…I decided to coat a
stone with boric acid/alcohol then sprinkle powdered charcoal on
top. I heat everything until the glass forms then allow it to
cool a little so I can scrape the charcoal off the top of the
prongs then flux and retip. The charcoal creates a reducing
atmosphere on top of the stone and also slows down the cooling
process.

Hmm. I’d guess if the charcoal helps, its only due to an
insulation effect. A reducing atmosphere isn’t really what you
want with sapphire or ruby. These stones are aluminum oxide.
While a reducing atmosphere is good for our metal and solders, it
is NOT good for an oxide based material. An overly reducing
atmosphere can actually cause the aluminum oxide to be reduced
to aluminum. You can do that with a sufficiently reducing flame,
resulting in a weird multicolored film on the surface, that even
if it then oxidizes again, has deteriorated the quality of the
polish a bit. Not as bad as does the etching attack from boric
acid or borax or flux on the stones (aluminum oxide, just like
the other metallic oxideds you are trying to prevent on your
metal, is nicely soluable in the boric acid or flux. The etching
these materials do is not from fusing to the sapphire, it’s from
dissolving their way into it a little. The resulting glaze of
both boric acid and dissolved aluminum oxide is still soluable in
pickle, so it does completely pickle off again, but leaves a now
etched surface on the sapphire that requires repolishing to
repair.

The trick(s) is this: The sapphire is not excessivly soluable
in just boric acid, at least not at lower temps. Keep the more
active fluxes off the sapphire at all costs, but a little boric
acid will be OK, IF you then don’t heat the sapphire or ruby hot
enough to actually glow (keep the stone under about a thousand
degrees) and if the time at whatever high temp is kept to an
absolute minimum. Plus, since we’re often working with at least
slightly reducing flames, a glaze of boric acid will in that case
actually protect the stone from the reducing effects of the
flame. On the other hand, it then risks etching from that boric
acid if the temp gets higher than a fairly low level.

So lightly fire coat your piece if you like. It’s your option
whether to wipe off the excess boric acid that you can reach,
from the stone, especially the visible crown areas, which are not
only most visible, but also most at risk of getting hotter.
Depends much on what sort of flame your using and where you’re
working. Work in such a way that your flame is directed at the
metal, but not at the stone. You can solder on a prong without
having to get the stone glowing… A small tight neutral flame
will work with both the stone and the solder. Not oxidizing, but
not all that soft and reducing either. If you work carefully,
like this, and confidently enough so you’re not taking longer
than needed, you’ll not have troubles with etching the sapphire.
Initial heating and subsequent cooling can, and should, be
gentle. You’re trying to minimize heat shock to the sapphire
too, as well as keep it from getting any hotter than needed.

But it’s important to realize that this procedure will always be
a balance between risks and costs. Always examine the stones
carefully before working on them. Ask yourself if you can afford
to have something go wrong. If the answer is no, then unset the
stone and do the job the harder, but safer way. If the stone is
within the range you feel comfortable about being responsible
for should something happen in spite of your precautions, then go
ahead and work as I’ve described. But do remember that this
whole procedure is a series of tradeoffs. It’s NOT guaranteed,
and even the old pros will occasionally have a sapphire get
accidentally fried…

Peter Rowe