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Faceted stones not sparkling once set


#1

Hi there,

I have taken a few stone-setting courses but really don’t know much
about faceted I am curious: oftimes when I set small
faceted stones (either tube-setting or flush) they lose their
sparkle and appear flat and dark in the piece.

I am wondering if this is due to the size of the stones (between 2 to
4mm usually), the quality of the stones (I usually buy cheaper
stones, often machine-cut) or due to the choice of setting (or the
quality of the setting i.e. the setter -:). It was my understanding
that light does not need to come from behind i.e. the facets on top
control the gemstone’s sparkle, so a setting which is closed from
behind should still allow the stone to shine. Oh, fwiw, I work
primarily in Argentium.

Any input would be greatly appreciated!

Kaia.


#2
It was my understanding that light does not need to come from
behind i.e. the facets on top control the gemstone's sparkle, so a
setting which is closed from behind should still allow the stone to
shine. 

For properly cut facetted stones, especially those with higher
refractive indices, this is correct. If the loose stone, with light
shining from the top down onto the table of the stone, looks nice and
brilliant, with light reflecting back to you, then it is capable of
looking the same once set. Stones cut too deep or too shallow, or
with too low an R.I., may still let you see through the stone to
what’s behind it, and with those, whatever is behind the stone will
affect how the overall finished set stone looks. it’s not that the
stone needs light from the back (though for those see through ones,
it can be nice), but simply that those stones function as partly a
window, rather than a reflector by themselves.

However, this fact that well cut stones do not derive their
brilliance from light that comes in from the back, is not the whole
story. An open back may not allow more light to be viewed from the
top, but it DOES let you clean the stone. And a clean stone is
critical. If the back facets have any grease, oils, wax, polishing
compounds, cleaning solutions, or the like on them, or trapped in a
closed cavity behind the stones so they can get on the pavilion
facets, then those dirty facets will not be able to properly reflect
light. The principal reason why drilling through the metal behind a
stone is important is to allow proper cleaning. Even a well done
bezel or flush set stone, despite seeming sealed into it’s setting so
as to exclude dirt from getting behind, will still eventually get
dirty in there. Oils, soaps, liquids, etc, just seem to find a way,
and without an opening behind the stone, you can’t clean it out.

there’s also other factors to consider. Any set stone will appear
somewhat dominated by it’s setting. A bezel or prong or flush set rim
around the stone obscures a bit of the stone, and puts the back in
shadow. The light entering the side or back of a stone may not be
responsible for the brilliant reflections, but a stone opened up on
the back and sides, is simply more visible, more transparent looking,
and will often look slightly brighter or lighter at least, as well
as simply looking slightly larger since less of the stone’s diameter,
girdle, etc, is hidden or covered by metal.

You also say you’re using cheaper quality goods. Be aware that often,
the cutting quality of these is more variable, and as I said above,
if the stone is not fully brilliant (this term refers to the light
reflecting from an overhead source back to the viewer as bright
reflections in the stone) to begin with, the setting will make it
look darker, by putting the windowed area in shadow. If the stone is
fully brilliant and well cut, and the back of the stone is properly
clean, then after setting it should still be just as brilliant.

Peter Rowe


#3

Kaia -

If a stone is properly cut with regard to its refractive index, then
there should be little light loss out the bottom or sides of a stone.
In the pursuit of carat weight or color, or just the limitations of
the rough material, you may find most stones are not cut to optimum
proportions.

This is especially true of inexpensive stones. No matter whether cut
by machine or by hand, if the refractive index is ignored (so as to
maximize color or carat weight, or cut away a flaw/inclusion) then
you will have lifeless stones when bezel-set (tube/flush, etc).

best regards,
Kelley Dragon


#4

Kaia:

I’m a faceter. It sounds like the problem is the quality of the
stones- they should reflect light from the table, and shouldn’t need
any back light. As long as your setting lets light into the crown
(above the girlde), the problem is the stone.

It isn’t easy to see with such small stones, but if you can see
through the stone, it isn’t cut well- see the picture here

http://www.theimage.com/faceting/facet5a.htm

My wife is a jeweler, and she gets stones in that size range from Rio
Grande. They aren’t perfect when you look at them through a loupe,
but they sparkle brightly enough.


#5

pierce the tubes, and open backings, undersides, etc. light must
come through at all possible angles to reflect off the facets… size
doesn’t matter if the stones are stones that sparkle anyway (by
nature some don’t.: clarity is not always sparkly!.) machine cuts
make it easier to calculate identical settings. native cuts mean
bigger girdles usually…but easier to set than a thin machine cut
girdled stone… just let light in and buy decent stones from
reasonably priced suppliers…rer


#6

Could be one of several possibilities…

The stones are not fully cleaned after polishing

The stones got chipped/broken during setting

Most colored stones still use some light from the back, shroud it
too much and it darkens

Nothing wrong with machine cut melee in cheap stones

When your done, loupe your work


#7

I think everyone knows the disappointment of buying a startling
stone only to find that it doesn’t perform that well in the workshop.
Rather akin to acquiring a racing greyhound or football player. It
looks like a runner in the kennel or college - but runs to fat and
lethargy once it’s out of the bright lights.

If you’re buying in person always take the material away from the
dealers showcase and into natural light! If it’s a football player
take them to McDonald’s!

Cutting a colored stone well means that a compromise must be made
between retaining a good color and maximizing the refractive
qualities.

Well faceted stones sparkle because they reflect/refract a high
percentage of light internally. They are cut so that as much of the
light that enters from the front is refracted and then, hitting an
internal back facet, is reflected and then exits from the top.
Likewise the light entering from the back and sides of the stone is
refracted so that it also exits through the top facets.

When stones are set so that light cannot enter from the back and
sides of the stone (closed setting) the amount of light seen from the
top is considerably reduced.

This is especially true of stones that do not have a very high
refractive index, such as quartz, and which are cut for depth of
color rather than ideal refraction.

I think it a good idea to mock up a setting for some stones as you
design rather than just allow oneself to be influenced by their
appearance on a piece of white paper. Often holding the stone in the
crook of your fingers or the crease of a piece of black paper will
reveal the difference.

For example… polishing the internal faces and base of a bezel will
help to reflect light that escapes from the bottom of the stone (the
pavilion.)

When making some decorative elements for church and synagogue objects
I’ve used concave mirrors made of highly polished white gold under
stones so that extra light was collected and reflected through the
stone. This even works for smaller jewelry.


#8

I make bezels for all my stones, and I’ve noticed that particularly
when I’m making stud earrings with smaller stones - which inherently
are closed backed - some of the sparkle can be lost. For all other
applications, I therefore make them open-backed for that reason.
Larger stones, such as 10mm don’t seem to lose much if any sparkle,
but the smaller ones can.

Helen
UK


#9

Did they look ‘flat and dark’ before you set them?

kpk


#10

Maybe the stones are dirty? Light doesn’t have to come from behind
the stone, but if a bunch of crud (polishing compound, skin
moisturizer, catfood, whatever) has managed to sneak in underneath a
stone, especially on settings that don’t have an open back, the
stones can become foggy and lusterless. Kind of like seeing soap scum
through the bottom of an otherwise clear glass.

That was what I was always taught at least, that the open back of a
setting is to make cleaning easier, not to let light bounce through.
If your stones allow it, I’d try a nice soak in a heated ultrasonic
followed by a steam cleaning.

Willis


#11

Hi Kaia

oftimes when I set small faceted stones (either tube-setting or
flush) they lose their sparkle and appear flat and dark in the
piece. 

If your stones are set with closed backs, you are most likely
getting polishing compound or ultrasonic solution or something behind
the stones, which will deaden and darken them considerably. I NEVER
set transparent or translucent stones in closed back settings in my
own designs, only opaque ones. I’m currently working with a designer
who insists on setting cab cut blue topaz in a closed setting. No
matter what I did, I always got some bit of dust or water trapped
behind the stone. I finally convinced him to set the stone down in a
bed of opticon before moving the bezel in around the stone. That
works, but it’s a pain. And I can’t guarantee what it’ll look like in
10 years. So, once again, I am going to re-iterate my number one
principle of design 101 for amateurs (not inferring you are one).

Problem #1, The Bigger Hammer.

When you find yourself looking for some “trick of the trade”, some
special gizmo or material that only the pros know about, or some top
shelf technician who can pull of anything, you are a victim of the
bigger hammer syndrome. Look at the design, ask the opinion of
others, get ready to abandon any part or all of the idea. Maybe
you’re right, there is someone or something that will make it work.
Equally possible is that you’re doing something that a good designer
just simply wouldn’t consider in the first place. There isn’t any
point in staying so attached to an idea that you end up settling for
a version of it that you’re not satisfied with anyway. Let it go,
your brain is an unfathomably powerful resource for ideas… exercise
it.

And you jewelers out there doing work for designers… if you look
around and find yourself spending money on better lighting, better
magnification, the tiniest burs, extra-extra low temperature
solders, weird little implements to polish down in holes, etc…
you’ve getting sucked into somebody’s bigger hammer scenario. Just
say no.

David L. Huffman


#12

Get Russian cut or fancy cut or well cut stones, not the cheap stuff.
BIG difference!

John Dach


#13
this fact that well cut stones do not derive their brilliance from
light that comes in from the back, is not the whole story. 

I quoted Peter, but there were a couple that came near - I’ll spell
it out, though. One good test for “Is it diamond or CZ?” is to set
it, table down, on top of some print or a steel rule. If it’s
diamond, you won’t see it through the pavilion because all of that
light is going back out the table. If it’s CZ you can see it clearly,
because the light goes through it’s a different RI. That only works
with round stones, BTW.

All of the light goes back up out of the table ONLY if it’s a
diamond - for a “diamond cut” stone, that is. That’s how Tolkowski
designed the moder n brilliant cut, is by basing it on diamond’s RI.
Other stones, cut to the same dimensions, will leak more or less
light depending on their RI. Worst of all maybe quartzes. And even a
diamond will go dark if there’s polishing compound stuck behind it -
especially on the girdle.


#14
And you jewelers out there doing work for designers.. if you look
around and find yourself spending money on better lighting, better
magnification, the tiniest burs, extra-extra low temperature
solders, weird little implements to polish down in holes, etc...
you've getting sucked into somebody's bigger hammer scenario. Just
say no. 

Say no to better lighting and magnification? I think I understand
your bigger point, but I’m sorry, could you explain that part? Good
lighting is critical to just about anything a human could possibly
do, jewelery related or not, and I consider my microscope to be the
best “big tool” purchase I’ve ever made. I might not really need
it, but it’s certainly made my life a great deal easier.

Willis


#15
One good test for "Is it diamond or CZ?" is to set it, table down,
on top of some print or a steel rule. If it's diamond, you won't
see it through the pavilion because all of that light is going back
out the table. If it's CZ you can see it clearly, because the light
goes through it's a different RI. 

This is terrible test.

First, see-through in CZ is only slight, - which means that, one has
to look for it. This test should be reserved for simulants like GGG,
YAG, and similar.

Second, simulants like Strontium Titanate, Synthetic Rutile, and
others with RI higher then diamond, or approaching diamond - are
going to fool you every time.

The most important point is that there are no simple single test for
diamonds, or any other This is very dangerous and
expensive notion to have.

Leonid Surpin
www.studioarete.com