Type IIa diamond w/ fluorescence (question)

[Texas Leaguer]

First let me say, I LOVE GIA. I have from the day I took my first lab and met my instructors so many years ago. (A small piece of trivia - one of them was John Yantzer, brother to Peter of AGS lab fame and to Phil, Director of the GIA lab.) Wonderful folks!

But the cynic in me can't help thinking that the 1997 Fluoro article by GIA was percipitated by a need among diamond manufacturers ( a huge global constituency of the GIA) to sell their slow moving fluoro goods.

This article is more scientific and objective and less of a basic survey with a lot of inherent potential for bias. And it leverages new technologies. While I have not yet decided whether this article helps the fluoro cause or hurts it, it is also aimed at justifying the major change that was made at the lab in terms of the color grading environment. I am not saying they are wrong. But if the goal is to demonstrate fluoro as a benefit in this research, they may have won the battle but lost the war.

If they actually do apply the new transparency model by including a transparency metric on future GIA reports as they tease in the article (and which I wholeheartedly believe they should do since consumer protection is their stated mission), they may succeed in putting to rest many concerns about haziness as a result of fluorescence, but open Pandora's Box regarding a whole lot of mainstream diamonds with transparency deficits!

 

[Garry H (Cut Nut)]

We are talking about apples and oranges.
Yes hazy discounts should be based on clarity not florescence.
However, the color grade or non-fancy diamonds is the material color not the face up color.
Uv in the grading lighting can interfere with getting an accurate material color grade in highly uv reactive stones.
That uncertainty deserves a discount.
Even gia acknowledges that there is an uncertainty and they just dismiss it based on trade tradition.

1. Karl you know now that the UV that causes N3 excitation passes through windows (contrary to what you believed when Michael Cowing used a measurement device that measured UV wavelengths that were too short to cause the most blue whitening effect).
2. You ignored the huge change in discounts - what discount chart would you establish as both an arm chair scientist (like me) and a market observor?
3. Are you happy that consumers are ripped off when they buy a fairly rare colored diamond in a fancy shape and recieve a yellowish diamond?

Who cares about rarity of material on a forum where well over half the participants are buying G-F VS2 -SI1 way better than average cut quality diamonds to look at an enjoy?

 

[Garry H (Cut Nut)]

First let me say, I LOVE GIA. I bash them a lot but they are the best there is Bryan

While I have not yet decided whether this article helps the fluoro cause or hurts it, it is also aimed at justifying the major change that was made at the lab in terms of the color grading environment. I am not saying they are wrong. But if the goal is to demonstrate fluoro as a benefit in this research, they may have won the battle but lost the war.

I am not sure which way you are going Bryan - do you believe GIA DiamondDock color grading lighting post 2000's has less UV or more UV?

Plainly in my view they never actually said much about the previous lighting.
(That Marty Haske hated and Michael Cowing quoted a D diamond that graded H by the once upon a time honest EGL lab when UV was filtered out with Lexan).
Not only did they reduced the amount of UV they increased the distance from the lamps.


This was the belated G&G article:

https://www.gia.edu/doc/Coloring-Grading-D-to-Z-Diamonds-at-the-GIA-Laboratory.pdf

 

[Texas Leaguer]

I am not sure which way you are going Bryan - do you believe GIA DiamondDock color grading lighting post 2000's has less UV or more UV?

I'm referring to the change to the GIA's original and longstanding practice of color grading in a UV free lighting environment in order to evaluate the true body color of the diamond. It's clear that there ensued an overgrading problem when that change first occurred. It may have since been corrected or mitigated by changing the grading distance from light source. It appears this new article is partially aimed at justifying their current practice.
As I said, they may not be wrong.

 

[yssie]

Clouds and Internal graining Yoram.
And this is from earlier this year but as yet un published.
I took the images from Cutwise.com - strong blue fluorescent stone - there are plenty of other examples there.
The numbers are from paint from the same spots


Yun Luo found similar results but she quantified using a different metric.

Measurement and Characterization of the Effects of Blue Fluorescence on Diamond Appearance | Gems & Gemology

Using customized, image-based measurement systems to quantify the effect of fluorescence on the color, brightness, and transparency of gem diamonds viewed in both face-up and table-down orientations.

www.gia.edu

Thanks for linking that article!

I’d like to raise one consideration:


Increased UV excitation
= increased luminosity
= increased brightness assuming unchanged viewing conditions.

And increased brightness
= increasing the entire range of tones across the board by the same amount
= decreasing
(lightest tone - darkest tone)/(average tone)
= reduced contrast.

The observed changes in contrast difference do not correlate with strain intensity or diamond type, strongly suggesting that the contrast loss is primarily due to fluorescence.

Speaking specifically to this statement at the end of the Results section - what I wrote above regarding increase in brightness alone decreasing perceived contrast is true in any context, not just with diamonds! And it’s true regardless of the reason for the brightness increase - fluor could be one reason for that. As in - reduced contrast may be one side effect of what fluorescence causes (which is - a measurable increase in luminosity). I guess whether or not this reduction in contrast actually occurs with blue fluor will depend on fluor strength of course, but also diamond body tone? Calling @Cerulean fact check me here.

I love the idea of contrastiness as an independent metric.

 

[Garry H (Cut Nut)]

I'm referring to the change to the GIA's original and longstanding practice of color grading in a UV free lighting environment in order to evaluate the true body color of the diamond. It's clear that there ensued an overgrading problem when that change first occurred. It may have since been corrected or mitigated by changing the grading distance from light source. It appears this new article is partially aimed at justifying their current practice.
As I said, they may not be wrong.

Bryan the history was that, led largely by Martin Haske who I think you were aware of, attacked GIA for overgrading blue fluorescent diamonds because GIA lamps emitted too much UV.
Others of us noticed that some of the Strg and VS diamonds in the 1997 article were clearly over graded and lower in color in the photos presumably taken in light with lower UV output.
Around 2000 GIA changed their lamps and began to use Diamond Dock with the shelf to lock in the distance to the tube.

So could it be that you missed all of that?
Do you still question it?

 

[Karl_K]

1. Karl you know now that the UV that causes N3 excitation passes through windows (contrary to what you believed when Michael Cowing used a measurement device that measured UV wavelengths that were too short to cause the most blue whitening effect).

You must have me mistaken for someone else. :}
It has been well over a decade that I saw for myself that they were using the wrong uv wavelength.
Diamonds were reacting to cheap uv led lights at 400nm more than expensive gia blessed testers.
Then I researched windows and window film to find out that 400nm passes right through it.
I have been with you there all along.

My position is that as long as the color grade is a material grade it is wrong to test it in lighting conditions that are known to change the grade that is not material color.

Face up grading brings on its own issues that may eliminate many fancy shapes from bring cut and also make an even bigger mess of rough planning and mine pricing.

 

[Garry H (Cut Nut)]

ntlemenYou must have me mistaken for someone else. :}
It has been well over a decade that I saw for myself that they were using the wrong uv wavelength.
Face up grading brings on its own issues that may eliminate many fancy shapes from bring cut and also make an even bigger mess of rough planning and mine pricing.

Good, I would have thought so
The bigger problem for fancies is again part of the GIA mess - they still seeem to be locked into parametric cut grading. It will never work!
Fix that and will stop producing 70% rounds.
So many consumer facing problems in our cottage industry.

GIA make + half a billion a year and do not pay tax.
Fix it ladies and gents

 

[Garry H (Cut Nut)]

Thanks for linking that article!

I’d like to raise one consideration:


Increased UV excitation
= increased luminosity
= increased brightness assuming unchanged viewing conditions.

And increased brightness
= increasing the entire range of tones across the board by the same amount
= decreasing
(lightest tone - darkest tone)/(average tone)
= reduced contrast.


Speaking specifically to this statement at the end of the Results section - what I wrote above regarding increase in brightness alone decreasing perceived contrast is true in any context, not just with diamonds! And it’s true regardless of the reason for the brightness increase - fluor could be one reason for that. As in - reduced contrast may be one side effect of what fluorescence causes (which is - a measurable increase in luminosity). I guess whether or not this reduction in contrast actually occurs with blue fluor will depend on fluor strength of course, but also diamond body tone? Calling @Cerulean fact check me here.

I love the idea of contrastiness as an independent metric.

The drop in contrast is very very slight and as a result of gaining some blue in the black obstruction zones only.
Obstruction is over done - the blackness from obstruction is about half for almost everyone looking at diamonds compared to what we see in photos and scopes.
And give me some more blue in a D to QR diamond any day.

 

[Texas Leaguer]

Bryan the history was that, led largely by Martin Haske who I think you were aware of, attacked GIA for overgrading blue fluorescent diamonds because GIA lamps emitted too much UV.
Others of us noticed that some of the Strg and VS diamonds in the 1997 article were clearly over graded and lower in color in the photos presumably taken in light with lower UV output.
Around 2000 GIA changed their lamps and began to use Diamond Dock with the shelf to lock in the distance to the tube.

So could it be that you missed all of that?
Do you still question it?

No. If you have followed my commentary on fluorescence through the years, I am very aware of the history. And as I said, GIA may not be wrong in justifying their current practices with their new technologies and approaches to the subject.

But it is also reasonable to question it.

I am not nearly as interested in the overgrading issue today as I am in the transparency issue, and the new things GIA is bringing forward on that topic.

 

[Texas Leaguer]

Thanks for linking that article!

I’d like to raise one consideration:


Increased UV excitation
= increased luminosity
= increased brightness assuming unchanged viewing conditions.

And increased brightness
= increasing the entire range of tones across the board by the same amount
= decreasing
(lightest tone - darkest tone)/(average tone)
= reduced contrast.


Speaking specifically to this statement at the end of the Results section - what I wrote above regarding increase in brightness alone decreasing perceived contrast is true in any context, not just with diamonds! And it’s true regardless of the reason for the brightness increase - fluor could be one reason for that. As in - reduced contrast may be one side effect of what fluorescence causes (which is - a measurable increase in luminosity). I guess whether or not this reduction in contrast actually occurs with blue fluor will depend on fluor strength of course, but also diamond body tone? Calling @Cerulean fact check me here.

I love the idea of contrastiness as an independent metric.

@yssie , You point up an important aspect of this study. To what extent is a technically measurable increase in luminosity due to fluoro (presumably a positive) have an impact on visual appearance? And to what extent is a technically measurable decrease in contrast (presumably negative) a detriment to visual appearance?

I don't think the article really resolves this question. Yes, they provide controlled digital imaging, but they also state a caveat about digital imaging being an imperfect technology.

Despite the title of the article being about both measurement and appearance, it seems pretty definitive about measurement and relatively vague on appearance.

 

[Garry H (Cut Nut)]

@yssie , You point up an important aspect of this study. To what extent is a technically measurable increase in luminosity due to fluoro (presumably a positive) have an impact on visual appearance? And to what extent is a technically measurable decrease in contrast (presumably negative) a detriment to visual appearance?

I don't think the article really resolves this question. Yes, they provide controlled digital imaging, but they also state a caveat about digital imaging being an imperfect technology.

Despite the title of the article being about both measurement and appearance, it seems pretty definitive about measurement and relatively vague on appearance.

Bryan do your own study by checking out Cutwise.com - search for fluoro diamonds as I posted on the page earlier.
You surely should question any research, but I have just had many of my studies confirmed and I am sold - here again - tell me what part of the out door is not better than the UV free????

 

[yssie]

Bryan do your own study by checking out Cutwise.com - search for fluoro diamonds as I posted on the page earlier.
You surely should question any research, but I have just had many of my studies confirmed and I am sold - here again - tell me what part of the out door is not better than the UV free????

I'm a bad person to ask because I actively prefer modern RBs in the I/J/ish colours over colourless. A very white stone is genuinely just not something I like on me. But the mellow welcome that near-colourless RBs exude IRL doesn't convey well in photos.

 

[Garry H (Cut Nut)]

I'm a bad person to ask because I actively prefer modern RBs in the I/J/ish colours over colourless. A very white stone is genuinely just not something I like on me. But the mellow welcome that near-colourless RBs exude IRL doesn't convey well in photos.

Partly because most vendors use too cold a color in their lighting so people think they are getting whiter stones Yssie.
But if you make sure your home is fitted with warm white LEDs (and draw the blinds in daytime) there will be no fluoro effect. Or take up dracularism and use candles?

 

[yssie]

Partly because most vendors use too cold a color in their lighting so people think they are getting whiter stones Yssie.
But if you make sure your home is fitted with warm white LEDs (and draw the blinds in daytime) there will be no fluoro effect. Or take up dracularism and use candles?

Now this is#problemsolving

Very glad to see Common Knowledge evolvingt to stop blaming haziness on fluor

 

[Garry H (Cut Nut)]

Common Knowledge to stop blaming haziness on fluor

And when did it become common?
Where and when did it become common Yssie

 

[Karl_K]

This is gia's position on and its wrong:
"The last but perhaps most important challenge is the standardization of illumination for color measurement and visual observation. In King et al. (200, the GIA team concluded that a standard light source for diamond color grading should possess key daylight elements—including a UV component to truly and accurately represent how a diamond appears to the human eye. For the results of this study to ultimately have significance for the diamond trade and its practices and regulations, we require an illumination standard that includes UV content and thus accounts for the effects of fluorescence on diamond appearance."

They are using the confusion of a material color grade vs appearance color to justify having UV in the color grading lights.
I do not buy that at all.

Measurement and Characterization of the Effects of Blue Fluorescence on Diamond Appearance | Gems & Gemology

Using customized, image-based measurement systems to quantify the effect of fluorescence on the color, brightness, and transparency of gem diamonds viewed in both face-up and table-down orientations.

www.gia.edu

 

[Karl_K]

Some other points: their own graph shows a stronger response at 400nm but continue to use the wrong value leds.
Also they are under driving the leds by varying their power and leds are only binned based on the specified drive perimeters. Any variation from that will results in unpredictable results.
The 5% power test could be a vastly different wavelengths than the full power tests and any in between differ even more.
Much of the testing was done on plates, not polished stones with complex interactions.

 

[Karl_K]

"Polished Diamonds. Patterns of bright and dark areas produced by light interacting with the facets of a well-polished diamond create a mechanism by which an observer can gauge the transparency of that diamond. When a diamond is very transparent, these patterns are perceived to be high in contrast, while for less transparent stones the perceived contrast is reduced—dark areas are less dark, bright areas less bright."

No, all bright/dark contrast other then extreme leakage/fisheye is environmental. Virtual facets reacting to the environment.

 

[Garry H (Cut Nut)]

Some other points: their own graph shows a stronger response at 400nm but continue to use the wrong value leds.
Also they are under driving the leds by varying their power and leds are only binned based on the specified drive perimeters. Any variation from that will results in unpredictable results.
The 5% power test could be a vastly different wavelengths than the full power tests and any in between differ even more.
Much of the testing was done on plates, not polished stones with complex interactions.

Karl much of what you say is correct or close to right. This is a committee run stodgy organisation - so cut them some slack - they are turning a big ship around in the direction we prefer.

Here is some accurate fluoro information from OctoNus that I have posted many times. And you are correct - often None or Faint fluoro diamonds show quite a lot of fluorescence with a cheap UV torch. But that just point out that even violet visible light adds some blue to a lot of diamonds.

 

[diagem]

The way fancy colored diamonds are graded.
It is not fair that a consumer who wants a colorless 1ct cushion and reads online that I will be safe - and they end up owning a crushed ice cushion facing up L color.

And you should know my stance on the issue of FCD's..., I don't think its fair to charge hefty fancy premiums on cape colored diamonds just because they face up darker by cut designs that really just compromise on the most important optical common sense for diamonds..., its play of lights!

I believe if its a rare fancy color, it should be observed and enjoyed from all viewing directions and not just one that is rarely observable in real life..., and certainly not at the price of light play potential.

Now back to your scheduled program....

 

[Texas Leaguer]

This is gia's position on and its wrong:
"The last but perhaps most important challenge is the standardization of illumination for color measurement and visual observation. In King et al. (200, the GIA team concluded that a standard light source for diamond color grading should possess key daylight elements—including a UV component to truly and accurately represent how a diamond appears to the human eye. For the results of this study to ultimately have significance for the diamond trade and its practices and regulations, we require an illumination standard that includes UV content and thus accounts for the effects of fluorescence on diamond appearance."

They are using the confusion of a material color grade vs appearance color to justify having UV in the color grading lights.
I do not buy that at all.

Measurement and Characterization of the Effects of Blue Fluorescence on Diamond Appearance | Gems & Gemology

Using customized, image-based measurement systems to quantify the effect of fluorescence on the color, brightness, and transparency of gem diamonds viewed in both face-up and table-down orientations.

www.gia.edu

I tend to agree with you Karl. This is a reiteration of the original justification for their change in color grading philosophy. Not sure I buy it.

If color grade was assigned on appearance instead of an accurate measure of body color, ideal cuts would consistently get better color grades from the lab. This would conflate two of the four C's.

 

[Texas Leaguer]

Some other points: their own graph shows a stronger response at 400nm but continue to use the wrong value leds.
Also they are under driving the leds by varying their power and leds are only binned based on the specified drive perimeters. Any variation from that will results in unpredictable results.
The 5% power test could be a vastly different wavelengths than the full power tests and any in between differ even more.
Much of the testing was done on plates, not polished stones with complex interactions.

It's important to remember that the original purpose of measuring fluorescence was simply to document an additional identification factor. It was not really intended to be an indication of performance or appearance. Therefore, a convenient standard wavelength was chosen and all diamonds observed against that standard. Reasonable approach.

Today, with much debate about the appearance and performance effects of fluoro, and the advent of an array of new fluoro stimulating devices the discussions have become much more arcane.

 

[Texas Leaguer]

And when did it become common?
Where and when did it become common Yssie

Not Yssie but you have to have your head in the sand not to know that haziness is THE biggest concern for shoppers considering fluorescent diamonds.

While potential overgrading of color was a bigger factor driving discounts in the trade, from a consumer standpoint potential haziness is clearly the bigger concern.

 

[josieKat]

If color grade was assigned on appearance instead of an accurate measure of body color, ideal cuts would consistently get better color grades from the lab. This would conflate two of the four C's.

As a psychological scientist, I've read many of these discussions with interest wondering where the perceptual studies are! I haven't yet had the time to do some poking around in academic sources, but surely someone out there has paired up with a psych person who does visual sensation and perception in order to quantify these things? (I often have this thought when it comes to size differences - I definitely see a difference of less than .2 mm in 2d pictures, but would need to do a perceptual test to see if that is reliable in real life and 3d, if there are consistent individual differences, etc - same for the color differences). The methods for just noticeable differences (JND) and also how to measure preferences is out there for the taking - you just need to collaborate with a psych person who is also interested in diamonds!

 

[Garry H (Cut Nut)]

If color grade was assigned on appearance instead of an accurate measure of body color, ideal cuts would consistently get better color grades from the lab. This would conflate two of the four C's.

I do not understand the reticence of you guys to full and open disclosure of color to consumers.
If people want rare material they buy D Flawless.
But 99% of people want a nice looking diamond that looks good in most lighting environments.
So why not grade D-Z diamonds the same way that we grade fancy colored diamonds?

 

[Garry H (Cut Nut)]

It's important to remember that the original purpose of measuring fluorescence was simply to document an additional identification factor. It was not really intended to be an indication of performance or appearance. Therefore, a convenient standard wavelength was chosen and all diamonds observed against that standard. Reasonable approach.

Today, with much debate about the appearance and performance effects of fluoro, and the advent of an array of new fluoro stimulating devices the discussions have become much more arcane.

The world gets new technologies and grows and develops. We have electric windows in cars and phones with more computing power than rockets sent to the moon had.

So why should we have 70 year old standards?
Why should a 15 year old cut standard pass 70% of round diamonds as having Excellent cut quality.
The entire system has so many flaws - it needs an update

 

[Garry H (Cut Nut)]

Not Yssie but you have to have your head in the sand not to know that haziness is THE biggest concern for shoppers considering fluorescent diamonds.

While potential overgrading of color was a bigger factor driving discounts in the trade, from a consumer standpoint potential haziness is clearly the bigger concern.

Of course Bryan, and so few vendors have bothered to offer consumers the benefit of strong fluorescence and screen out hazy diamonds.
When will White Flash start doing it - or is it OK to continue to spread the fear?

 

[Garry H (Cut Nut)]

As a psychological scientist, I've read many of these discussions with interest wondering where the perceptual studies are! I haven't yet had the time to do some poking around in academic sources, but surely someone out there has paired up with a psych person who does visual sensation and perception in order to quantify these things? (I often have this thought when it comes to size differences - I definitely see a difference of less than .2 mm in 2d pictures, but would need to do a perceptual test to see if that is reliable in real life and 3d, if there are consistent individual differences, etc - same for the color differences). The methods for just noticeable differences (JND) and also how to measure preferences is out there for the taking - you just need to collaborate with a psych person who is also interested in diamonds!

We had a serious crack at this seven years ago with human perception of cut quality. I believe this article may be 10 or 20 years ahead of it's time.

https://www.researchgate.net/publication/263843604_How_diamond_performance_attributes_brilliance_scintillation_and_fire_depend_on_human_vision_features

 

[Texas Leaguer]

Of course Bryan, and so few vendors have bothered to offer consumers the benefit of strong fluorescence and screen out hazy diamonds.
When will White Flash start doing it - or is it OK to continue to spread the fear?

Who's spreading fear Garry? Certainly not me. Please don't misrepresent my commentaries.

My record is very clear, and recorded here on the forum for years for anyone to review. My positions are not the least bit hazy.