I can see it will take studying many stones to be able to
judge what is an acceptable amount of windowing. I am gaining a
better understanding of what it is I am seeing. But I still have to
deal with this issue when setting the stones that have varying
degrees of windowing and see-through. It seems even if the facets
are distorting what is underneath the stone, you are still
glimpsing something under there. Do you think bezel settings make
this effect appear more pronounced?
Carrie, before responding to your question, I’d like to tell you for
the record that I received my G.G. from GIA at age 46, after
studying and appreciating gemstones for a large part of my life.
That being said, I would like to encourage you to keep noticing the
things you have been noticing, such as the reality of how gems
appear, as opposed to what the textbooks say. I mention this to you
basically because I have had long arguments in the past here about
this very subject, and the textbooks will disagree with what I am
about to type, and so do many people. And so, I plunge again…
What you will read in the book is that a gemstone cut as perfectly
as possible with regard to its’ critical angle (and other
proportions, as well) will have all light enter through the crown,
bounce around inside, reflecting and refracting many times before
every bit of that light exits back through the crown to the viewer’s
eye with no windowing, and no extinction. For purposes of
illustration, the texts use the wave theory of light, and eschew the
particle theory. For the same purposes, one narrow, BEAM of light is
illustrated. The reality is that we never (except under strict
controlled conditions) observe a gemstone under that condition.
Light hits it from practically every angle, in waves and in
particles, inside of 180 degrees relative to the crown (or girdle),
and from every direction. Some of that light will always enter at an
angle that will leak out of the pavilion. When it does, some will
also be reflected back.
This is particularly evident when there is a color around the
girdle. You’ll eventually learn about cases where diamonds have been
“colored” by marking around their girdles with simple colored
markers. The color reflects through the stone, imparting a false
bodycolor to the stone. In fact, natural green diamonds get their
bodycolor from a thin “skin” of green that is (with very few
exceptions) only on the surface. They are cut specifically to leave
a bit of that “skin” on the girdle (called a natural), which imparts
the green bodycolor by reflecting it throughout the stone. This
evidence alone proves beyond argument that bezel settings assuredly
can make this effect appear more pronounced. You mentioned that you
recognize the fact that it will take studying many stones to judge
what is an acceptable amount of windowing. I agree, and I challenge
you to have fun in doing so.
The stone of mine that originally started my questions, I
honestly think looked better when there was a solid gold backing
behind it. I think the metal was compensating for the stone
leaking light, and the metal was bouncing some of the light back up
through the stone. When I cut an opening, I could see the lack of
reflected light that was the opening and the difference between it
and the remaining metal backing. When I enlarged the opening, it
looked better because there was no more contrast of opening and
backing metal, there was just opening. But the stone is darker.
Still quite pretty but there is less light reflected back. So in
setting a stone like this, I still don't know that there is any
best solution. I guess the only solution is choosing a stone with
less light leakage. It just seems such a common problem with
colored stones.
Everything you typed above is valid, and open to discussion. But
what really matters is, you recognized what looked best. Much like
the lapidary who windowed the dark stone, you noticed that the solid
backing looked better. Please don’t feel as though there is not a
“best solution.” In the case of the stone you mention, it appears
you found it with the solid backing. In the future, you will select
stones that not only have better proportions, but better color, tone
and saturation, as well. As you look at more and more stones, you’ll
notice that some just look better - you even said as much here:
“I have come across many stones that have this problem (windowing)
in varying degrees, though I did not have the terminology to
describe it until now. I just knew that something was not right.”
Dear Carrie, please continue to SEE what you’re looking at. If it
“just doesn’t look right,” search for one that does look right. And
continue reading as you have been. By learning from textbooks,
you’ll learn the terminology of what you’re seeing, and what to look
for. But by handling and SEEING, you’ll make better purchases and
more beautiful jewelry. After all, jewelry is best seen (or worn),
not theorized about. And eventually, you’ll just KNOW what type of
setting will yield the best look for your chosen stone.
A tip: Get a pair of quality gem tweezers and hold every stone you
consider selecting with them. Look at the stone with overhead
lighting and a neutral background, such as a sheet of white paper.
In your other hand, take a pencil, pen, chopstick, solder pick,
etc., and move it back and forth behind the culet of the stone. Did
you see it moving behind the stone(windowing), or not? Next, note
the color and tone of the gem, then place it on your hand, face-up,
between two fingers. Let the culet rest in the crease formed between
your fingers. Did the color or tone (lightness or darkness) change?
The percentage of windowing matters less than how much the color and
tone of the stone changes when worn, if you see what I mean.
Don’t get me wrong, I value my GIA training and hold it in high
regard. In fact, I am more proud of it than any other academic
accomplishment, and I’d recommend it to anyone who wants to learn
ten or forty years worth of industry knowledge in a very short time.
But picking what looks good to you will never serve you badly. Some
of what I learned with GIA is simply BS. Theory is a great way to
lend understanding, but reality sometimes blows theory out of the
water.
James S. Duncan, G.G., A.J.P.
A.K.A. James in SoFl
