Do ECs face up whiter?

[Alexiszoe]

I know popular wisdom says that ECs show body color more. However, over the years I have also heard a few jewelers who say that ECs face up whiter than their actual body color, although I never paid much attention...until a recent diamond shopping trip with my friend, which made us do an about turn.

We looked at several H / I/ J color emerald cuts and beautifully cut RBs, side by side. The emerald-cuts we saw faced up as white as the RB in the same color (with the exception of 1). These diamonds had minimal fluorescence too.

Does anyone know what's happening here? Also, what is the rationale for saying emerald cuts exhibit MORE body color? And how about others who say that it exhibits LESS body color?

 

[valeria101]

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Another step cut myth: the model is said to be rare in fancy colours - and it is, because it does not enhance colour enough ...

The story of how aparent colour might be controlled +/-, seems exceedingly complicated to pin down more ! Not mine to tell - WWW

I would expect that it is possible for a particularly reflective EC to work as optical bleach with simple, broad, bright flash & not much contrast from second order reflections ... But this is not a common EC at all & other kinds of 'optics' give the same impression to me - I know not why ...

Nice problem !

 

[Karl_K]

Diamond color is lighting dependent.
In many lighting conditions and the better cut the diamond your not seeing the body color, your seeing the light return.
They are different things.
Shift the lighting slightly blue and yellow is further suppressed.

A classic ec with a large table shows body color more often than a mrb across all lighting conditions.
An EC also tends to concentrate color in the corners due to end to end long light paths.
Which is why they are not often used in colored diamonds because it is very hard to make the color even across the stone.
The ones that are cut use material that would get fancy dark in other cuts.
The center does indeed lighten perceived color because the light paths tend to be in and out and the stones are narrow.
So an EC at the same time can hide body color and enhance it with fancy colors.
Weird eh?

 

[diamondseeker2006]

I'd say that might depend on the color. I have seen an O color AVR that faces up whiter than an N AVC which has bigger facets. But when you look at near colorless stones, I do not think it is the case that the ECs look more tinted. But really, there's just no way to fairly compare a brilliant cut with a step cut or large faceted antique stone. My antique asscher is K color, but it looks white most of the time because it is well cut.

So basically, I don't buy into generalized statements like that!

 

[valeria101]

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Perhaps a nice example for the uneven colour play @Karl_K wrote about:

K (IGI) - WWW

FY (GIA) - WWW

 

[rockysalamander]

I think and additional factor is that our eyes can detect more color in step-cuts than in brilliant cuts. Why? With brilliant cuts, there are lots of little facets that throw off high intensity light. Your eye responds to that by contracting the pupil. A small pupil makes color detection harder.

Asschers with more smaller facets and royal asschers are a bit harder than a EC to detect color due to the faceting.

Think of looking at two flowers in the garden under bright direct light. They may look the same. But, take those two flowers indoors and you'll find that shades and intensity may vary. How much this affects individuals will vary greatly. Some people see color more than others and some people tolerate bright light more than others.

 

[Karl_K]

.

Perhaps a nice example for the uneven colour play @Karl_K wrote about:

K (IGI) - WWW

FY (GIA) - WWW

yep!
You rock, I was doing some virtual images in DC and in the same time you found some real images which is even better!

 

[Karl_K]

I think and additional factor is that our eyes can detect more color in step-cuts than in brilliant cuts. Why? With brilliant cuts, there are lots of little facets that throw off high intensity light. Your eye responds to that by contracting the pupil. A small pupil makes color detection harder.

Asschers with more smaller facets and royal asschers are a bit harder than a EC to detect color due to the faceting.

Think of looking at two flowers in the garden under bright direct light. They may look the same. But, take those two flowers indoors and you'll find that shades and intensity may vary. How much this affects individuals will vary greatly. Some people see color more than others and some people tolerate bright light more than others.

I think you have something there.

 

[valeria101]

@Karl_K

Just happened to have the two saved from a somewhat recent attempt to understand YF's sermons about contrast & colour WWW ! I am quite surpprised of how strongly coloured the same Y-Z looks in very low light, side-ways & back-wards, with not much brilliance there at all (WWW) - perhaps very long light paths for those errand sparkles ? [a DiamCalc question, perhaps]

Digressing

 

[Karl_K]

Val,
The longer the light path the more color.
This is why so many colored radiant cuts are on the market.
The rough that could be cut into a Q colored round can be cut into a fancy yellow radiant if the rough shape supports it.

 

[diamondseeker2006]

@Karl_K

Just happened to have the two saved from a somewhat recent attempt to understand YF's sermons about contrast & colour WWW ! I am quite surpprised of how strongly coloured the same Y-Z looks in very low light, side-ways & back-wards, with not much brilliance there at all (WWW) - perhaps very long light paths for those errand sparkles ? [a DiamCalc question, perhaps]

Digressing

I have the twin to that stone, and it honestly looks nothing like the pictures Yoram has on his site! So I am not sure what to make of that other than his photogrpahy is showing something different than it's actual appearance (although that one does have fluorescence)! Mine does have great light return, but I see an even, saturated very light yellow!

 

[diamondseeker2006]

And to the points about K color, I think my antique asscher does look whiter than the K EC in the JA video. Maybe partly because of the smaller facets, and maybe because IGI wasn't as strict as GIA in grading that particular stone. My K has far less color and doesn't show concentrated color in certain areas. In the picture below, the colors are K, I, Y-Z, top to bottom.

 

[valeria101]

I have the twin to that stone, and it honestly looks nothing like the pictures Yoram has on his site! So I am not sure what to make of that other than his photogrpahy is showing something different than it's actuall appearance! It does have great light return, but I see an even, saturated very light yellow!

I did mean to ask exactly this !

Have you seen the diamond loose ? [no patence to browse for the answer ... ]

 

[diamondseeker2006]

Caysie got the stone directly from Yoram, so I never saw it unset. But here is a picture she took:

 

[valeria101]

.
The transformations are surreal ... If these were three diamonds, they wouldn't match !

 

[Alexiszoe]

.

Another step cut myth: the model is said to be rare in fancy colours - and it is, because it does not enhance colour enough ...

The story of how aparent colour might be controlled +/-, seems exceedingly complicated to pin down more ! Not mine to tell - WWW

I would expect that it is possible for a particularly reflective EC to work as optical bleach with simple, broad, bright flash & not much contrast from second order reflections ... But this is not a common EC at all & other kinds of 'optics' give the same impression to me - I know not why ...

Nice problem !

You brought up an interesting idea, I never thought of fancy colors and emerald cuts in that way before!

Calling @Rockdiamond , in your experience with fancy colors is it true that emerald cuts do not enhance color enough due to the way it's cut? As an EC lover who has seen a lot more diamonds, what are your thoughts on emerald cuts showing more body color - or is it actually better at hiding them?

 

[Alexiszoe]

@diamondseeker2006 , you have a beautiful collection! That asscher is divine

@Karl_K , you mentioned "the longer the light path the more color" hence there are many radiant fancy cuts. Could you explain what this means? I understand the whole "crushed ice" look (e.g. radiants and ends of ovals and pears) concentrates color more, but I am unsure what the light path here means.


I also wonder other than shape how much a well cut step cut diamond can mask body color. We saw 2 J color emerald cuts - one faced up tinted while the other was whiter - and both graded by GIA.

 

[Karl_K]

EC will lighten the color in the center and increase it on the ends with colored rough.
It is often used for rough that would get a dark designation in other cuts and a few tricks are played with the ends to get it even enough.
Getting the color even across the stone is very hard to do.
Rounds are also cut from this type of rough.

Light path is how the light travels in the diamond from where it comes in and where it goes out.
In an EC light that goes from side to side is a short light path, light that goes end to end often bouncing around is a very long light path.

 

[Karl_K]

Shows the uneven color if the stone is cut the same as a colorless.

 

[Karl_K]

Short light path == less color


long light path == more color

 

[Karl_K]

Btw one trick to even out the color is to make the parts that would be dark a bit leaky. That will make the biggest difference, there are other ways to make smaller adjustments.

 

[Karl_K]

I also wonder other than shape how much a well cut step cut diamond can mask body color. We saw 2 J color emerald cuts - one faced up tinted while the other was whiter - and both graded by GIA.

ECs and SEs/asschers are a bit of a different story so should be considered separately.

Cut can make a large difference in color, there is so much variation in cut that without knowing more it is hard to pinpoint it.
Also J is a very wide range(about the same as D-G), its possible for a i/j border to appear white to someone and a j/k border yellow.
It boils down to that persons color perception.
My bet is on cut.

 

[Karl_K]

btw that virtual image is the stock model in diamcalc and it would not be acceptable to cut it that way but its good enough to show what I wanted to show.

 

[Rockdiamond]

You brought up an interesting idea, I never thought of fancy colors and emerald cuts in that way before!

Calling @Rockdiamond , in your experience with fancy colors is it true that emerald cuts do not enhance color enough due to the way it's cut? As an EC lover who has seen a lot more diamonds, what are your thoughts on emerald cuts showing more body color - or is it actually better at hiding them?

I would defer to Karl for the technical aspects. From a practical standpoint: it's true that emerald cut is not preferred by the vast majority of fcd cutters because their goals are generally to get the deepest color. In most cases that will equate to the highest net price.
I remember a case where an amazing FCD cutter ( now retired ) who asked me to come look at a stone he was working on. It was one of the most gorgeous Light Yellow emerald cuts I've seen. Almost 5cts.
He asked me what I predicted the GIA would grade the stone. I said Fancy Light Yellow- and he agreed.
I was heartbroken when I learned he'd cut it into a 4 ct radiant cut. GIA gave it Fancy Yellow- so the net value was higher than when it was an emerald cut.
Part of the issue is the even color a radiant can produce as compared to an emerald cut. As Karl has shown, color tends to "bunch up" in an EC.
It does not bother me as I see it as an intrinsic aspect of the cut. BTW, FCD pear shapes, marquise and ovals tend to share this aspect.
It with emerald cuts in particular it's generally accepted that you'll get less color than a properly cut radiant or cushion.

In colorless emerald cuts I find a very mixed bag. Sometimes a J EC can look very Yellow and other examples hide the color.
I'm sure if presented with individual specimens Karl could detail why this inconsistency exists.
From my hands on, non techie point of view I'd attribute it to differences in make. Corner size, crown and pavilion angle, size of girdle all play a part.

 

[Rockdiamond]

btw that virtual image is the stock model in diamcalc and it would not be acceptable to cut it that way but its good enough to show what I wanted to show.

You've got me curious Karl- why wouldn't this be an acceptable model to cut to? It looks pretty durn nice to me!
I will tell you that in many cases of FCD emerald cuts the cutters use "tricks" that you won't find in colorless. Things like cutting to 50% depth. Or with tables the size of Lake Michigan- yet still produce nice light performance.

 

[Karl_K]

You've got me curious Karl- why wouldn't this be an acceptable model to cut to? It looks pretty durn nice to me!

The wire frame above shows the issue and its the same from the top. The crown facets are very unevenly sized.
They should be to the eye the same size from the top to each other and the side to each other.
like this:

 

[Alexiszoe]

@Karl_K , thanks for your very informative posts, I am learning a lot! Given your explanation of long light path, I would assume that stones that are long / rectangular (i.e. pears, ovals, marquises and emeralds), would show more color because of how much light has to travel in order to bounce back out. As such, a squatty emerald-cut, with a shorter light path, would show less color?

Another thing that popped up in my head - since color is concentrated at the ends and the "windmills" (for lack of a better term) in emerald-cuts - wouldn't an asscher show more color because the windmills are longer as compared to say, an emerald-cut? I know it sounds contradictory to the whole light path thing - I am just trying to understand what's going on.

 

[Alexiszoe]

@Rockdiamond , thanks for sharing your experiences, it's really interesting to know what goes on behind the scenes! I remember you had a spectacular 6 carat fancy vivid yellow asscher? some time back...it always made me drool.

You mentioned differences in make could affect EC's face up color - could you expound on it a little more? Does that mean a well cut EC hides color - or it has to be cut a certain way (which may or may not necessarily be "well cut") to hide color?

Another thing I noticed is that fancy colors sometimes have similar colored cups to enhance the color of the diamond. Given this logic, would cups work for near colorless H-J diamonds to make it look whiter?

 

[Karl_K]

SE/assscher has the same issue with uneven color with colored rough.
But it is more variable than with a EC because the light paths are not as long. This is the same design as the one above just made square.

 

[Karl_K]

On the other hand.....