This way, often just a wooden or plastic dowel can get it the stone
out quickly and easily.
g’day Gary - I’ve a question that probably has a very obvious
answer, but not being a jeweller (I’ve set about 2 dozen stones in my
career, all badly) I’ve too curious not to ask it. If the stone is
set on a retaining shoulder or ledge, how does one remove it from
the back?
Al Heywood
Beth, I do very little with good stones but I’m wondering why you
don’t lay your stones out on a background that will match the
material that you will set them in?
Marilyn Smith
When I lay out stones for a design, I do it on a white pad
Beth, I totally support you in what you are doing. If a piece is
being repaired and it was foiled what do the non-foilers do? Repair
it to its original state and compromise, or make the customer deal
with what you think is right or wrong about foiling…
Some of us have been happily foiling for years, and will continue
to do so regardless of what is posted, because it achieves the effect
desired. I for myself believe it is a practical solution not an
ethical dilema. If someone used green foil behind a colorless beryl
and sold it as an emerald, that would be different than using foil to
bring out the natural color of a stone.
We sell silver that was made in Bali and some of the blue moonstone
pieces had blue backing that we did not know about till one needed to
be reset. Then we disclosed to the customers that were interested in
the remaining pieces that there was blue backing. Some cared, some
didn’t. All the pieces have been sold, and the customers who bought
them were really happy with what they bought. We have 5000 pieces of
sterling silver from all over the world. We cannot test every piece
to see how it was constructed,(cold solder joints the biggest
problem, stone setting second) and if each stone is natural. We
disclose that not all stones are what they appear to be. Have you
seen some of the large “peridots” in Bali silver?
I am a Graduate Gemologist in Residence, 1977. There are issues to
get in a tizzy about, and some that are not really threatening the
integrity of our trade.
Once again, whether it is foil backing or stamping karatage, I need
to be realistic based on my experience and the experience of others
that operate as I do, and assess my liability and the consequences. I
have been making jewelry for 30 years, retail for 15 years.
I do have some experience with how reasonable or unreasonable
people are. I have been threatened by a few customers that had
mental or emotional problems. I was upset at the time because there
was a communication problem and they thought it was all me, even when
I was trying to find out what they needed, and all they wanted to do
was blame and take out their hostility on me for something that was
probably going on in some other part of their life. Every one of them
left and I never saw them again. Being ethical, honest, and having
integrity is very important to me, I also need to be practical.
Cathartically yours, Richard in DenverBeth, I do very little with good stones but I'm wondering why you don't lay your stones out on a background that will match the material that you will set them in?
Hi Marilyn, If I understand your question correctly, you’re asking
why, if I’m going to set my stones in gold, don’t I design on top of
a gold-colored paper so that the colors stay true from the design
stage to the finished piece? That’s an interesting concept but it
doesn’t solve the problem. For instance, any light to medium
saturation blue cabochon placed on a gold-colored paper or set in
gold will turn some shade of green. Similarly, if the cab is light
to medium saturation pink, it will become peach or orange. So, if I
always laid out my stones on a gold background and then set them in
gold bezels, I’d pretty much have to eliminate blue and pink from my
color palette. And I’m not willing to do that!
Beth
Tony, I think you may be ( no, you are) wrong.
That’s what I meant. In a perfect cut all light entering the stone
through both the table and pavilion should be reflected and refracted
back through the table.
Tony Konrath
Gold and Stone
www.goldandstone.com
tony@goldandstone.com
That's what I meant. In a perfect cut all light entering the stone through both the table and pavilion should be reflected and refracted back through the table.
Except that’s not what happens, Tony. Most of the light entering
the pavilion of an ideal cut diamond (and most others) reflects off
the inner surface of the table, and instead of exiting, bounces back
toward the opposing side of the pavilion, where it exits. The visual
proof of this is simple. If you hold a diamond over, say, printed
material, you cannot read the text through the stone. If light
entering the pavilion exited out through the table, then the image
of what is under the stone would appear to someone viewing the stone
from the table direction. It isn’t. however, viwing a diamond from
the side, where most of the light enters the pavilion, lets you
pretty much look through the stone. Looking straight into the
pavilion facets, you can easily see things reflected in the table,
indicating that light entering the back which hits the table,
reflects, and does not refract out. Try it. Now, the optics of
diamond are optimized for light return from the table up position.
It happens that this doesn’t return much light that enters the
pavilion. But that’s not absolute. SOME of the light that enters the
pavilion, especially that which doesn’t just hit the table, but which
may enter at odd angles and end up hitting crown facets, may end up
bouncing around the stone several times, eventually exiting the
crown. Diamonds are just not very good at doing that. Some, yes.
Enough so the color of the metal, or whatever, that’s behind the
diamond does have some effect on the percieved color of the stone.
But it’s not a large effect. Mostly, it’s light exiting the crown at
oblique angles, as when the stone is tipped appreciably away from
straight toward the viewer.
Colored stones with lower refractive indices may allow more light
from the back to exit the front. When that happens, one of the
visual clues is a window, and the “read through” effect. In those
stones, what’s behind the stone makes a big difference in the
appearance of the stone.
Peter Rowe
Hi Marilyn, If I understand your question correctly, you're asking why, if I'm going to set my stones in gold, don't I design on top of a gold-colored paper so that the colors stay true from the design stage to the finished piece? That's an interesting concept but it doesn't solve the problem. For instance, any light to medium saturation blue cabochon placed on a gold-colored paper or set in gold will turn some shade of green. Similarly, if the cab is light to medium saturation pink, it will become peach or orange. So, if I always laid out my stones on a gold background and then set them in gold bezels, I'd pretty much have to eliminate blue and pink from my color palette. And I'm not willing to do that! Beth
Yes, you understood my question and I understand your desire for the
wider color palette. However, sometimes it can be broadening to have
boundaries to work against and it could be a selling point to say
that the color is not artificially enhanced. by foiling. What you
see is what you get sort of thing. Marilyn
Peter, I think you would be hard pressed to demonstrate light
entering the pavilion of any well cut stone. In the last paragraph you
mention colored stones with lower refractive indices. Just for
those who may not know: if you stick a stick in water it looks like
it’s broken where it enters the water. That’s because light travels
at different speeds depending on the medium it is passing through.
Many of the stones ( crystals) we use are cut with this in mind. A
stone properly cut will not allow light to leak out. On the other
hand, a windowed stone is improperly cut and will allow light to leak
out of the pavilion or other places diminishing the brillance of the
material. The “lower refractive index” is not better than a high
r.i.; it’s just different. Each stone, that has a crystalline
structure, has an appropriate refractive index because of the way
light behaves in that particular material. These comments apply only
to stones that have a crystalline structure and to the oddball opal
that can possibily be faceted. KPK
Yes, you understood my question and I understand your desire for the wider color palette. However, sometimes it can be broadening to have boundaries to work against and it could be a selling point to say that the color is not artificially enhanced by foiling.
I have to disagree again, Marilyn. There are plenty of other
boundaries inherent in what we do already. Believe me, I am not
lacking for challenges! I don’t consider creating another one –
unnecessarily – to be broadening. In fact it would be narrowing to
be forced to limit my color palette, given the stone intensive nature
of my designs.
I would also question your statement that I’m artificially enhancing
the color of the stone by foiling it. Most loose stones are
displayed against a white background, such as a gem paper, cotton, or
just a white plastic dish. There’s a reason for this: A gold
background would distort the color of the stones. Some aquamarines
are more blue than green; some the other way around. If I take a
blue-hued aquamarine cab and set it directly over gold, I change the
color to green. Now that’s much more artificial than setting it over
silver foil. I used to line my gold bezels with a thin piece of
silver. Would that bother you less, since it’s another precious
metal? I switched because silver tarnishes and foil doesn’t. Both
achieve the same effect: They maintain the truer color of the stone
while providing a metallic effect. Beth
I used to line my gold bezels with a thin piece of silver. Would that bother you less, since it's another precious metal? I switched because silver tarnishes and foil doesn't. Both achieve the same effect: They maintain the truer color of the stone while providing a metallic effect. Beth
I have followed this post with interest as well as some amusement.
When I was working in the jewellery store we outsourced our repairs
to a goldsmith who picked up and dropped off repairs twice a week. I
remember one time I had noticed that a customers ring in 18k yellow
had white claw settings for the stones. I remember the goldsmith
groaning and asked why this was done. He said exactly what Beth has
been stating, that white setting show the proper color of gemstones,
especially paler hued ones. He only groaned because they are also
somewhat harder to repair. He also said that many goldsmiths actually
use yellow claws and rhodium plate them to make them white as they
are then easier to work with.
Just my observations.
Finally spring has sprung with the latest spring on record here in
Calgary. We are 1 month behind for growing. Karen Bahr “the
Rocklady” (@Rocklady) May your gems always sparkle.
I seem to be taking the devil’s advocate side in this discussion and
I want to point out again that I do very very little faceted stone
setting and don’t make my living as a jeweler so I have no real
emotional stake at risk. At one time, I painted a lot of abstracts
(well, actually, they were three dimensional shapes with only
two colors and yes, I was in school) and it made a real difference
which two colors were used. The edge where they met could play visual
games with the human eye. Color as color is still very interesting to
me and that is probably where my interest in this discussion lies.
Marilyn Smith
Peter, I think you would be hard pressed to demonstrate light entering the pavilion of any well cut stone.
I belive that’s exactly what I said. In a well cut stone, the
viewer does not see light that has entered the pavilion of the stone.
however, if the stone is trasparent, light does indeed enter the
pavilion, just as, if it hits any other facet, like the table,it also
enters. It’s just that the light that enters the pavilion generally
does not exit through the table or crown in a direction which is
visible to the viewer from a table up position. But, for example,
take any well cut diamond, and view it from the side. You can see
right through the pavilion to the other side of the pavilion. Not
clearly, of course. But move a needle behind the stone and you’ll see
partial broken images of the needle through the stone. Thus light is
entering the pavilion, in this case, viewable also through the
pavilion. You’ll see more of this if you look, from the pavilion
side, into the stone towards the inner surface of the table. In that
surface, you also will see reflected light that entered the
pavilion. Again, it doesn’t affect the table up appearance of the
stone very much, but if you intended to say that no light enters the
pavilion, that statement is a bit too broad, unless you’re talking
about a well cut foilback (grin).
... In the last paragraph you mention colored stones with lower refractive indices. Just for those who may not know: if you stick a stick in water it looks like it's broken where it enters the water. That's because light travels at different speeds depending on the medium it is passing through. Many of the stones ( crystals) we use are cut with this in mind. A stone properly cut will not allow light to leak out. On the other hand, a windowed stone is improperly cut and will allow light to leak out of the pavilion or other places diminishing the brillance of the material. The "lower refractive index" is not better than a high r.i.; it's just different.
Each stone can be appreciated for it’s own merits. But those with a
higher refractive index allow a wider range of pavilion angles to be
used without getting a window or an area of extinction (another type
of light loss, where instead of seeing through the stone, you just
see a dark shadow. It’s due to too steep a pavilion angle instead of
the too shallow angle that gives a window) Because of this, as a
general rule, stones with higher refractive indices are usually
capable of being cut with greater brilliance (light return). As you
say, this is not necessarily better, only one of the many factors
that makes each stone a unique type of material.
Each stone, that has a crystalline structure, has an appropriate refractive index because of the way light behaves in that particular material. These comments apply only to stones that have a crystalline structure and to the oddball opal that can possibily be faceted.
Here I must correct you. Materials don’t need a crystal structure
to have a refractive index. Clear glass, with no crystal structure,
has a refractive index. so do transparent liquids. What you’re
referring to is the fact that those crystaline materials which have
crystal systems OTHER than cubic, because of the fact that their
lesser symmetry means the optical environment can be different
depending on the direction through the crystal that light travels,
or depending upon the vibration direction (polarization direction),
light may travel at different speeds within the same material. That
means that the refractive index can vary with direction, or
polarization direction of the light. Such materials are known as
double refractive, and they do something that non-crystaline
materials, or cubic materials (except when strained) don’t do: They
split light into two polarization directions as it enters ion any
direction other than directly along an optic axis, and each
polarization direction has it’s own refractive index, as well as,
sometimes, a different color. The result is that gemologists have a
whole bunch more that can be obtained by measuring the
refractive index of a material, or more importantly, the appearance
of a stone can do wonderous things, like showing double images though
the stone, or two or three colors to the same stone, at once, through
different directions. It’s why stones like ruby can be puplish red
in one direction and orangy red in another, or a long thin topaz can
be pinkish peach at the ends and yellower color in the middle, as
light travels across the stone for the latter color, and end to end
for the former. Or try Tanzanite, which before the heat treatment
that leaves it nice and purple, is reddish in one directly, blueish
in another, and yellow in a third (heat treatment removes the yellow,
so the overall muddy brown color of the untreated stone becomes a mix
of the blue and red directions.)
cheers
Peter Rowe
Seems that this thread has moved on a bit … the initial enquiry
related to cabochons and low cut stones, but now most of the
discussion is relating to faceted gem-stones. My two pennuth on
this, and perhaps on the yellow diamond thread too, relates to the
matter of refractive index.
The figures quoted in text books relate to the case where diamond,
or some other material of interest has an interface with plain old
air. Physicists prefer the interface to be with a vacuum, but in the
real world… But, often the stone surface isn’t perfectly clean
(and we’re talking very thin layers of contamination here), and so
there can then be light leakage, in both direction (light paths are
reversible) where you wouldn’t expect it in an ideal theoretical
case. Grease, sweat and so on can all cause this. And yes, grease
and sweat can get between a stone and a tight prong.
Kevin (NW England, UK)