The optics of bezel settings

[raddygast]

This may seem like an unusual question. But take a look at the ring posted below.

Now, how much would such a setting impact the optics of the stone it enclosed, in terms of brilliance, dispersion, scintillation, and perceived color?

I thought that, in theory, with a perfectly cut stone (which we never get with colored gems), all the light that comes to our eyes has basically travelled in through the table and crown facets, gone through the gem, bounced off the pavilion facets, and back out through the crown to our eyes.

If that is the case, then, in theory, a full bezel setting will not affect the color, true? But I am inclined to think that there is quite a bit of light that enters in from the sides and so forth, though perhaps this never travels back out through the table.

Basically, I just want to get a theoretical idea about how much full bezels "swallow up" the beauty of a stone. Aesthetically speaking, I much prefer them to anything with prongs. A half-bezel is about as open as I''d be willing to go, and if I were going to use an oval, I would definitely go half-bezel as it opens up more of the gem and makes it feel more substantial, chunky, and weighty. But with an emerald-cut shape, I think full is the only option (if anyone has seen a semi-bezel for a square or rectangular-shaped stone, please forward me a link!)

Also, will the color of the metal actually affect the apparent stone color? I know that a ruby viewed on a gold plate will look redder, due to the gold absorbing more of the non-red wavelengths before bouncing it back out through the gem. But in most settings, the pavilion is free and clear under the prongs or bezel or whatever, is it not? So the metal color shouldn''t affect it.

I hope someone can give me some advice or assurance about this.

 

[strmrdr]

A bezel setting will make some stones look darker in color than some more open settings.
Why?
Light from the back and sides tends to wash out the color and the bezel blocks it.

 

[strmrdr]

My bottom line is mount light stones is bezels and mount overly dark stones in open settings to lighten them up.

 

[Hest88]

I agree with Strm in this one. Think of a stained glass window. The more light you get from behind your sightline the lighter the stone will appear.

 

[elmo]

Plus you're looking at spinel, right? I think if red spinel has a tendency it's to be over color or dark-toned

.

 

[Michael_E]

raddygast,
The apparent color of a stone will change in a bezel depending on the refractive index of the stone, the angles of the stone, the saturation and starting color of the stone, the color of the setting, the amount that the bezel overlaps the edge of the crown, the type and direction of the ambient light and how far the stone is tilted when you are viewing it. Basically, low R.I. stones will show a window through their sides, as they are tilted, sooner than a higher R.I. material. Aqua will start to show a window at maybe 5 degrees, sapphire at closer to 10, CZ at close to 30 and diamond at close to 50 degrees of tilt, in well cut round stones. This is even more pronounced in emerald cuts like you''ve shown in your picture. Since many stones will show this window when tilted, you will be looking through the stone at the inside of the setting. Bezel settings are generally closed on the sides, so you will see the stone as being darker. With lighter colored stones, you will also notice a slight reflection from the bottom of the bezel as it wraps over the edge of the crown. Ad this slight color to the color of the inside of the bezel through the window and all of a sudden that blue aqua can start to look a bit greenish.
Diamonds have such a high R.I. that these effects are much less pronounced, but they still exist. I think that one of the reasons that bezels look darker on diamond is that as you tilt the setting you don''t get any sparkle through the side of the stone like you would with a prong set stone. This discussion sort of points out one of the drawbacks of diamond cut grading in that everyone''s trying to find the "perfect cut", when in use, that diamond is not just viewed perfectly face up, but at many other angles. Real world use of gems is with a dynamic view, yet grading and then choosing a setting comes from an almost static view of the stone and its "performance".
Back to bezels. If you really want to combine the protective aspects and look of bezel setting with the known optics of a lower R.I. stone, you need to make some kind of allowance for light to enter the windowing area as the stone is tilted. This is most easily done by making decorative cutouts in the side of the bezel in some way.

 

[raddygast]

Thanks guys.

This would be for a spinel, yes, but one with a tone that is not too dark: between medium and medium dark. Still, that may be too dark. Also, the RI of spinel I think is 1.725 or something like that, and I believe that''s lower than corundum and definitely lower than diamond or garnet.

Like I said, horizontally set ovals in a half-bezel setting can be quite nice. Attached a pic from the same jeweller (though it''s a cab, that was the best example of the half bezel). And I think they allow for a lot of light-play. But I still don''t completely understand the purpose. If when tilting the stone, the light is leaking out through the sides, it''s not coming back to your eyes so the saturation and tone seem washed out. In a bezel, that would keep the light in, which is in theory good to deepen the color, but I suppose it can go too far and make the stone look inky.

Once again, I am wondering if anyone has ever heard of a half-bezel for a squarish stone. It''s probably never done, but I''m not convinced it would look terrible. It might look interesting.

 

[valeria101]

Big fan of bezels here

Any shape, any material... any time, basically.

On another therad you posted a light sapphire in one of Linda''s rings - that looked bright, no ? Sapphire and spinel have about the same optics, with spinel being slightly brighter in person (been told that this is because of it''s lack of double refraction, sapphire has a bit of that).

IMO, It doens''t make much sense to look at the second decimal of the RI. Stones are very different in person for 100 other reasons, the setting being just one of them.

 

[Matata]

Date: 1/14/2005 4

0:53 PM
Author: raddygast
Thanks guys.

This would be for a spinel, yes, but one with a tone that is not too dark: between medium and medium dark. Still, that may be too dark. Also, the RI of spinel I think is 1.725 or something like that, and I believe that''s lower than corundum and definitely lower than diamond or garnet.

Like I said, horizontally set ovals in a half-bezel setting can be quite nice. Attached a pic from the same jeweller (though it''s a cab, that was the best example of the half bezel). And I think they allow for a lot of light-play. But I still don''t completely understand the purpose. If when tilting the stone, the light is leaking out through the sides, it''s not coming back to your eyes so the saturation and tone seem washed out. In a bezel, that would keep the light in, which is in theory good to deepen the color, but I suppose it can go too far and make the stone look inky.

Once again, I am wondering if anyone has ever heard of a half-bezel for a squarish stone. It''s probably never done, but I''m not convinced it would look terrible. It might look interesting.

Raddy,

If you have photoshop (or if you ask Valeria really nicely) maybe she can play around with a pic of my ring. Perhaps she can turn my oblong into a square to give you an idea of what it could look like.

 

[raddygast]

Well unless photoshop does ray tracing I don''t think it can help!

I''m just worried not so much about how the stone will look in terms of its dimensions (or how the ring will look overall, which is quite to my tastes) but rather about how much less vibrant the color will look when set in a full bezel.

Now, this stone is length-to-width only 1.14 (I think). Still don''t have it in my hands quite yet. So I''m not quite sure, if I used some sort of half-bezel setting, which dimension to open it up in: the length dimension if horizontally set, the width dimension of vertically set. Horizontal is unusual and really attractive to me for ovals, but I think vertically (north-south) set EC''s just have that much more in-your-faceness about them.

But anyway: here are some pictures. Granted, I find most of them horrifically ugly, but they just give me some ideas about the possibilities for the head. What do you guys think. The pendant and that gold ring w/ blue sapphire are the simplest and most open, and they do look sort of nice. But just not as nice as the full bezel (also included). Any comments?

 

[raddygast]

attached

 

[valeria101]

Speaking of open bezels... how does the Lucida bezel sound ? There are versions of it here and there.

Perhaps something less intricate similar to the piece below(bar pave, say) could be done too:

 

[canuk-gal]

HI RG:

I am in the process of setting a tourmaline, and have decided on the half bezel option, because I like to see "more" of the stone and felt it will allow for better optics/viewing/showcasing of the moderate color change of the stone. Originally I wanted a full bezel b/c I am attracted to that "framed look", but felt in the half bezel I could get the best of both worlds (optics and impact).

cheers--Sharon

 

[valeria101]

this is Etienne Perret, but the half bezel version is done by others too.

Tacori uses this idea (left)

to suspend a diamond in the open and call it a bezel setting.
Sure there is more out there too.

 

[Matata]

Have you seen the stone yet? Maybe the right choice will be clearer once you post pics. I think full bezels are beautiful but my preference is for a very thin bezel. In that bottom right pic, the bezel overwhelms the stone. Here''s two more (east-west cause I think they are "hello in your face" pretty). Both are tsavs; first is a very dark stone, 2nd is brighter.

 

[Matata]

2nd.

 

[raddygast]

Thanks all.

canuk-gal: *do* post your ring, even pics of the waxes or similar designs, as soon as you can! I am inclined to do what you are doing.

to the rest: some of those pictures are quite nice. I sort of like matata''s first pic, and the Lucida bezel looks pretty interesting. I wonder if it would work for an EC.

I am hoping Michael_E stops by again to impart his wisdom about optics. Specifically, in a half-bezel setting, which area (being open) would benefit the stone most: the length, or the width (in an emerald step-cut stone, with not too long a length to width ratio).

 

[raddygast]

I''m sort of surprised that you can actually have the width-dimension enclosed and the length dimension exposed even with a north-south setting. Like so:

(i like the idea, not the ring):

 

[tonysgeko]

Raddy, here''s a pic according to the site it''s a burmese red spinel.

From harwinjewelers .

Both from boldingold .

 

[valeria101]

Someone mentioned this shop, opened the site and found lots of interesting airy bezels.. hence the post.

I wanted to comment on bezels' optics but somehow didn't get the right end of it. I definitely undertsand the comments about tilt brilliance and side windowns showing metal. I'd worry about that too for very light colored stones of say, 5 carats onwards. On a small stone the issue seems purely philosophical. For a stone with strong color, bezels might do some good that might not have all that much to do with brilliance, but more with color itself.
Ruby is sold on gold-colored background instead of hanging between tweezers like unset diamonds, and that's done for a reason - the color loks that much better on metal. I have always believed that colred stones look better in bezels because the colors look stronger, especially if the clarity is not perfect. Not sure what the theory behind could be - never gave it a serious experimental thought. However, it may be a matter of contrast - color flash from brilliance showing more on the darker surround just like contrast helps diamonds show off their fire and brilliance more.

Of course, A dark stone would not benefit much unless foil backed underneath that bezel ! But a dark stone that has been deliberately windowed to lighten the color might as well look better in a bezel especially if there is some crown height to catch light.

It must be easier to judge what works and how with the stone in hand, of course. General theory is always harder to spell out than just a particular comment.

 

[raddygast]

I''m still having a bit of difficulty fully understanding Michael_E''s post about tilt optics. He''s saying if you tilt the stone from the perpendicular (where there should be no windowing), depending on the facet angles and the RI, you will soon see a window, right?

I still don''t see why having it in a full bezel isn''t better -- because then the window wouldn''t really be there, i.e. the light would only escape out to the bezel wall and be bounced back in. Is he talking about light that would somehow ENTER through the sides and then reflect back up to your eye, which would now be blocked?

 

[spinel]

Check this site: www.mensjewelryformen.com
The man is a gemologist and is a high skill goldsmith. He can surely answer your question and help design your ring.

 

[strmrdr]

Date: 1/14/2005 11:34:18 PM
Author: raddygast
I'm still having a bit of difficulty fully understanding Michael_E's post about tilt optics. He's saying if you tilt the stone from the perpendicular (where there should be no windowing), depending on the facet angles and the RI, you will soon see a window, right?


I still don't see why having it in a full bezel isn't better -- because then the window wouldn't really be there, i.e. the light would only escape out to the bezel wall and be bounced back in. Is he talking about light that would somehow ENTER through the sides and then reflect back up to your eye, which would now be blocked?

There are a couple issues here:
I have a oval garnet that when light is allowed into the back of it shows a window.
Block the back light and the window doesnt show.
The stone needs the mirror effect of a darker background to cover the window.
A bezel setting would be perfect for it.

Other stones a bezel would make the window look worse because of the upward reflection of the light off the shiny bezel would make the window stand out more.

What he is getting at and what I said about the apparent color is that the gemstone itself and how its cut determin what type of setting it works best in.
It will vary on a stone by stone basis.

When having a stone custom cut by knowing the final setting its going into the cutter can pick a cut that works well in that type of setting.

For example the barion cut will increase the apparent saturation of a gemstone.
IE. make it look more colored.
The down side is that they tend to window more than some other cuts when looked at at an angle.
A bezel by limiting the angles that the stone can be seen can help.
In other cuts it may make it worse because the angles you can see it are the ones that show the worse window.

 

[Michael_E]

I might have created a couple of misconceptions in this discussion about windowing and bezel set stones so I''ll try to answer a couple of things that have been brought up here. First, tilt windowing in a stone is strictly related to it''s R.I. and it''s cut. The stones that show the least tilt windowing are round stones, because of their symmetry. As you move away from a round shape to shapes with longer aspect ratios, (that''s the length to width ratio for those not up on the techno babble), you get a greater difference in the pavilion angles between the short side and the long sides of the stone. If you try to use a standard brilliant pavilion, then the angles are going to be bad for either side or both sides. This is what causes "bow-tie" in ovals, marquises and pear shaped stones. In the early ''70''s Basil Watermeyer publicized a technique to overcome this problem, which came to be known as the "Barion" style of cutting gems. Check Jeff Graham''s site for a very good explanation and some pictures at: http://www.faceters.com/askjeff/answer14.shtml
These stones REDUCE windowing by making the angles on the lower part of the pavilion all very close to ideal, but windowing will still occur and generally in a triangular shaped area on the opposite side of the stone. It is truly a window, which means that light can go through it from both directions. By opening up the lower part of a bezel you are allowed to look out through the window at whatever is on the other side. If the bezel is closed you will see the inside of the bezel, which is generally very dark since it is shaded and even if the inside of the bezel is polished you would still need to have the light come into it from somewhere. Imagine looking into a paper tube lined with aluminum foil, still not very bright is it ?
Now as far as the bezel design is concerned, you can do whatever you''d like. A prong setting can be considered a special case of a bezel that has been cut out to leave only four or six thin strips of the bezel holding the stone. Imagine taking a plain, heavy cast bezel and piercing it in any number of shapes. You can even imagine "secret" shapes being engraved and pierced into the sides of the bezel so that you would only see that shape when the stone is tilted and showing a window. Or try this in your mind, imagine gemstones that are set into the sides of the bezel which are designed to "leak" any light that they "catch" back into the center stone to make it look as if it is glowing and brighter than it could otherwise be. There are so many things that you can do with the optics and mechanics of stone setting that it just boggles the mind.
One of the big advantages of the newer CAD programs is that they can do very fine and accurate renderings of these ideas at a very low cost. The one thing that is missing, as has been brought out here, is that these systems require skills and experience that can''t possibly come packaged with the systems and so they can be time consuming to assemble a good image of a proposed, unique piece of jewelry. BUT you can make a discreet library of all of the parts and shapes that may be used or modified to make nearly anything you can imagine, (including stones cut into completely custom shapes). As these systems get better and more complex, I would expect to see designers having the ability to make up a totally custom design to a clients specifications in a matter of an hour or less and then modifying it to look at various changes in an even shorter period of time. The end result could then be created and shipped in under a week with the client knowing exactly what they would be getting fro every angle, at a very reasonable price. Sounds cool doesn''t
it ? Much of this is available now and the rest is coming soon, so get your imagination fired up !

 

[strmrdr]

Hmmm,
"First, tilt windowing in a stone is strictly related to it''s R.I. and it''s cut."
true:
But is totaly dependant on the angle its viewed at.
If the setting blocks the worst angles the stone will appear better than it is.

Barion:
From the link above:
"Barions work best in materials that are lighter colored and larger sized. Because of their depth Barions tend to darken the finished color of a stone. They usually have a higher number of facets than a regular design of the same shape would and require more work to cut as well as larger stones ."

They will also almost always show the far side windowing you talk off.
The angle isnt right for it to reflect light back.
Its one of the downsides of the cutting style.
On my main computer I have a link to a site that discusses this but my main computer is down right now.