Can spinel withstand heat?
lemel_man
white spinels all round. It has sentimental value as it was the owner's
grandmother's. The mod would be no problem had the stones been diamonds,
but the prospect of removing and replacing all these little things is
not enticing. Can I solder the ring with stones in place without
damaging them?
--
Regards, Gary Wooding
(To reply by email, change feet to foot in my address)
Peter W.. Rowe,
<bins...@bigfeet.com> wrote:
>>I've been asked to modify a gold eternity ring that has little (1.6mm)
>>white spinels all round. It has sentimental value as it was the owner's
>>grandmother's. The mod would be no problem had the stones been diamonds,
>>but the prospect of removing and replacing all these little things is
>>not enticing. Can I solder the ring with stones in place without
>>damaging them?
yes, if you're careful. Spinels respond to heat much the same as sapphire. That
means avoid heat shock, by heating slowly and gently, more so than you would
with diamond, and cool slowly. In addition, like sapphire, spinel is an oxide.
That means that like the oxides on metals, it can be attacked by fluxes which
are, of course, intended to dissolve oxides. So unlike diamonds which must be
protected from oxygen while heating so they don't oxidize (burn), spinel is
already an oxide, and isn't harmed by exposure to air while hot. But it should
not be exposed to fluxes or boric acid fire coat, or for that matter, an overly
reducing flame, while hot, as all these can damage the surface. And overall,
try not to get them any hotter than you need to, as the hotter they get, the
greater the potential for damage. Choose the solder grade accordingly.
Note that this assumes the spinels are synthetic. If natural, take care to
avoid heating those with any inclusions. And take some solace too in the fact
that if you do damage one, they're very cheap. You'd then just smash the
broken one to remove it (thus not needing to actually unset it), and replace it
with a new one at a cost of pennies, but some time.
Peter
melis...@gmail.com
reference chart on hand? Spinels are not so common- at least in my
experience.
I use a heat shield on stones when I do repair work and I am unsure.
Stuller sells on that looks like a clear jelly
http://www.stuller.com/products/productdetails.aspx?iid=94894... it is
ok. Vigor used to sell on that looked like peanut butter
http://b2bprofessionaltools.net/HEAT-SHIELD-VIGOR-16-OZ-JAR/M/B000HYL1RK.htm
and it is much better.
I think you can find a guide to stones and sensitivities in the back
of the Stuller Findings catalog- which I have at my studio, but not at
home with my computer.
Peter W.. Rowe,
<melis...@gmail.com> wrote:
>>Peter- do you store all of that info in your brain or have a quick
>>reference chart on hand? Spinels are not so common- at least in my
>>experience.
Just in my head. I've never yet seen a chart I completely agree with, or that
is correct all the time on all issues. The best of them simply urge cuation to
varying degrees with just about everything...
But spinel is easy. When we're talking the synthetics, the two main ones, in
traditional use at least, are synthetic spinel, and synthetic corrundum, both
made by flame fusion methods. Separation is easy with a polariscope, or simply
by logic. The corundums are the reds, yellows, garnet colors, and other "warm
colors", while white is usually spinel, as are the light blues (dark blue can be
either corundum or spinel at times) and any of the greens. And of these, many
of those cool colors, especially greens, are actually also white spinel made as
triplets, so the color is just a glue line. These, by the way, can take no
heating. But the white spinel is made by flame fusion, as is corundum, so you
know as a matter of course that heat by itself won't hurt it. The risk, as I
pointed out, is heat shock from sudden heating or cooling, and this applies to
all stones that can otherwise take heat, even including to some degree, diamond,
although diamond is, if free of internal strain or larger inclusions, such a
good heat conductor that heat shock is less of a risk.
>>
>>I use a heat shield on stones when I do repair work and I am unsure.
>>Stuller sells on that looks like a clear jelly
>>http://www.stuller.com/products/productdetails.aspx?iid=94894... it is
>>ok. Vigor used to sell on that looked like peanut butter
>>http://b2bprofessionaltools.net/HEAT-SHIELD-VIGOR-16-OZ-JAR/M/B000HYL1RK.htm
>>and it is much better.
I've never liked any of these commercial products. Remember that they don't
actually change the behavior of the stone to heat, they just act as a sheild,
mostly to protect the stone from contact with the flame itself. Often the
stones still get exposure to heat from contact with the metal in the setting.
The insulating properties of the gels are a bit decieving, since much of their
real effectiveness rests on actually cooling the stone by being "wet", with the
moisture content acting then as the cooling agent. But with the gels, when the
metal gets hot, it tends to dry out the gell that's in contact with it, then
creating a slight insulating air space between metal./gem and the gel, but to
the user, the gel still looks wet ans sticky, even though it's no longer in
contact with the metal or gem, which now can be heating by conduction from the
metal.
I'm much more a fan of the somewhat messier, but free, older methods, that of
using actual liquid water in some sort of carrier to cool the stones. Simplest
is just a cup of water, with the ring or whatever immersed in it exposing the
joint but with the stones under water. No way the stones get over 212F that
way. When that's not possible, wet tissue paper wrapped around the area to
protect, sometimes held with a bit of binding wire, also serves the purpose, and
with these methods, the liquid water can still flow a bit, keeping the metal
wet. If things appear to be starting to dry out, more water can be applied to
the outside. Variations include using wet sand or soldering grain instead of
just the cup of water, or shredding up furnace tape or, as frosty recently
posted, powdered asbestos or similar mineral material to make, with added water,
a wet sort of paper mache goop. Again, because the water is less tightly bound
than with those gel like commercial products, it can flow in the mass, to keep
the surface of the metal wet.
>>
>>I think you can find a guide to stones and sensitivities in the back
>>of the Stuller Findings catalog- which I have at my studio, but not at
>>home with my computer.
To an extent, it's pretty simple. Most stones don't much like heat. A few are
especially sensative, and usually, they tend to be those that are fragile in
other ways too. Really only the synthetic spinels and corundums (those that are
not triplets or assembled) , diamond, some natural versions of the above, and to
a degree, other synthetics (CZ, for example, sometimes can take a good deal of
heat, but it's tricky at times...) can be heated in anything like a routine
manner. Some other stones can take some heat, like some of the red garnets, if
you're lucky. A few, the softer stones, organics, peridot, opal, emerald,
tanzanite, etc, are especially prone to damage. And some, like amethyst, are
particularly prone to color change with even mild heating. Most of the rest
we routinely use, are about the same, meaning you don't really want to get them
too hot either, though perhaps without the extreme risks some of the most
fragile ones pose. Other than diamond, it's safe to simply never heat any stone
you cannot afford to replace if damaged.
So like I said, I don't need a chart. If unsure, just assume it needs
protection from heat.
The best bet, of course, for many jewelers would be to actually bite the bullet
and get some formal training in gemology, during which you'll simple learn this
stuff about different stones. Given how much of the income for many jewelers
revolves around gems, it's always seemed odd to me how few jewelers seem to
obtain any formal training in gemology....
And trust your experience too. If a chart says a stone is safe for something,
buy you remember a time when it cost you a bunch of money to follow that advice,
then the next time you'll ignore the chart and be careful. One of the
costliest stones I ever had the misfortune to damage was a large medium light
blue sapphire. About 8 carats, heart shaped, in a platinum mounting. An area
of the mounting well away from the stone needed a small quick solder joint. The
stone never got hot enough to even begin to melt the boric acid fire coat I'd
put on to protect the many diamonds on the piece surrounding it, and I took care
not to direct the flame near the sapphire, so I didn't expect trouble. But I'd
failed to note the fairly large, but hard to see included crystal within the
stone. Probably there was some sort of liquid filled cavity in there too.
Because when I pulled the ring out of the pickle, the stone had shattered.from
stress around that inclusion. So much for charts saying sapphire can take some
heat. That particular stone could not, and for failing to examine the thing
carefully before I assumed it was safe to be heating the ring well away from the
stone but without other specific heat sinking, we paid a rather substantial
price for the replacement. And I know a guy who claimed he had never had a
problem with tanzanite in the ultrasonic, and couldn't understand what the
charts were talking about,. Well, one day he learned to the tune of a couple
thousand dollars. Costly lesson.
So if unsure at all, play it safe. When estimating a job for a customer, never
take chances with your wallet, or the jewelry if you have a choice. Unless you
know the stone will be safe, or know that a replacement if needed is
acceptable, and the customer/owner of the piece agrees, simply don't take the
risk.
And remember that charts are all prepared by humans. Humans make mistakes and
typos. Often charts are not researched as well as they should be, or are copied
from other convenient sources the publisher may have around. There are some
gemological charts out there that have perpetuated some very obvious mistakes
though several generations, including publication in full blown book form.
cheers
Peter
Frosty
smoke signal from lemel_man <bins...@bigfeet.com> rang out, which was
heard to say :
>I've been asked to modify a gold eternity ring that has little (1.6mm)
>white spinels all round. It has sentimental value as it was the owner's
>grandmother's. The mod would be no problem had the stones been diamonds,
>but the prospect of removing and replacing all these little things is
>not enticing. Can I solder the ring with stones in place without
>damaging them?
Were it me I might suggest to the customer that all the stones
*should* come out, then I'd redo/beef up each prong, for a price of
course.
lemel_man
They are tiny (1.6mm diam) stones that are beadset in a channel; it
would be easier to remake the ring than removing and resetting them all.
Many of them are worn and I think it would be better to replace them
with diamonds but, as I said before, it was the grandmother's eternity
ring...
Nuffsed?
Frosty
>Frosty wrote:
>> In rec.crafts.jewelry almost on Mon, 27 Aug 2007 02:29:00 -0700 a
>> smoke signal from lemel_man <bins...@bigfeet.com> rang out, which was
>> heard to say :
>>
>>> I've been asked to modify a gold eternity ring that has little (1.6mm)
>>> white spinels all round. It has sentimental value as it was the owner's
>>> grandmother's. The mod would be no problem had the stones been diamonds,
>>> but the prospect of removing and replacing all these little things is
>>> not enticing. Can I solder the ring with stones in place without
>>> damaging them?
>>
>> Were it me I might suggest to the customer that all the stones
>> *should* come out, then I'd redo/beef up each prong, for a price of
>> course
>
>They are tiny (1.6mm diam) stones that are beadset in a channel; it
>would be easier to remake the ring than removing and resetting them all.
> Many of them are worn and I think it would be better to replace them
>with diamonds but, as I said before, it was the grandmother's eternity
>ring...
>Nuffsed?
yeppers!