Article Over Grading of Blue Fluorescent Diamonds Revisited

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Look at this chart - I chopped off an experimental error - You can see there is excitation taking effect right down to very slightly greenish blue.

The 3D graph by Thomas Hainschwang on page 42 of the Cowing study illustrates the same concept, BUT with the added element of "intensity". Those results support the conclusion (same page) "At normal viewing distances from artificial illumination the violet light intensity, just like the UV, is too weak to excite noticeable fluorescence".

I could not manage to copy the chart seperately. Perhaps Michael can post it here.

Here is the chart as a screen shot. Higher resolution would be much easier to look at. Also, here is a quick link to the full 2010 study for convenience. (It is linked in the article being disussed here). http://www.acagemlab.com/temp/CowingOvergrading.pdf

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Stand by please.
I have ordered some equipment to make it clear and supporting evidence as to why Blue Fluorescence is good.

And GIA's approach to color grading is a reasonable approach.

I will prove that Michael Cowing's white LED grading light is the incorrect approach (at least until all lighting is LED and we all become vampires).

BTW, if anyone can help me buy a set of narrow band UVA and UVB LED's - the sort that have been discussed here a few years back - I remember it was possible to purchase half a dozen or a dozen that covered off several small band UV frequencies.

 

[Karl_K]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Stand by please.
I have ordered some equipment to make it clear and supporting evidence as to why Blue Fluorescence is good.

And GIA's approach to color grading is a reasonable approach.

I will prove that Michael Cowing's white LED grading light is the incorrect approach (at least until all lighting is LED and we all become vampires).

BTW, if anyone can help me buy a set of narrow band UVA and UVB LED's - the sort that have been discussed here a few years back - I remember it was possible to purchase half a dozen or a dozen that covered off several small band UV frequencies.

http://www.s-et.com/uvtop-catalogue.pdf
http://www.intl-lighttech.com/products/light-sources/leds/uv-leds
http://www.mouser.com/search/refine.aspx?Ntk=P_MarCom&Ntt=182788096

400nm nominal you can pick up anywhere as they are the most common.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Always an interesting discussion.
Taking a step back, let's look at color grading with a broader perspective from a color grader.
If you were given a parcel of ungraded stones, how would you determine the color of each stone?
Of course one of the first methods will involve using a master set of stones who's color is already determined.
If we're speaking colorless, or near colorless, you'll need to look through the pavilion, in a controlled lighting environment.
Since we have to have some standard, this is GIA's methodology, and we're all adhering to it.

The answer for me regarding any specific diamond, is that you would look at it in as many lighting environments as you can. Although I'm interested in what the color grade is, if I am considering purchasing the diamond, I'm more concerned with how the color actually looks in real life.
Look at a lot of stones and you'll see that not all diamonds with identical GIA color grades, will look the same in the real world.
Cut contributes of course, but also the material itself.

Florescence is a huge complication in all of this if we're speaking of consistency between GIA color grades, and actual face up appearance.
IMO, we will never be able to "solve" this issue because the diamonds simply won't allow it. They're going to behave how they want no matter what we discuss.
Do stones of Medium or Strong Blue look different face up than other inert stones that look identical viewed through the pavilion?
Some will, and noticeably so.

AS Garry points out- to be able to see the difference between a G and an I color, you'll need a fair amount of light.
Here's a relevant paragraph form the article we're discussing:

Not known to the trade until recently is that blue fluorescence is stimulated not just by UV, but also by the narrow band of “visible-violet” (VV) wavelengths from 390nm up to 415.2nm (the center of the absorption band of the N3 aggregate). The energy in this band is too weak to cause grade whitening fluorescence at typical viewing distances from artificial illumination, where a diamond’s unimproved color is seen.

This is the crux of the discussion.
The first part of the statement would seem to support what I've been saying all along- that certain MB. or SB stones will face up whiter than their inert counterparts in normal room lighting- which is bright enough to see the color difference.
The second part of the paragraph is overly broad and makes assumptions with no basis in fact. How can we know the UV, or VV wavelengths at any given moment in any given lighting environment? Furthermore, maybe there's other spectra of light activating he color whitening. Experience has shown me that some I colors with SB or MB will face like an H or even G. Not all, but a select few. In "normal" room lighting. I have not experimented with LED lighting specifically

 

[ame]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Wow. Incredible article. Fig 6a is where I actually said WHOA out loud.

I really liked your solutions to the problem in the conclusion, too. I am kind of surprised that it's still not rectified. Is it just not a widely known issue?

ETA: As someone who has a stone that has been graded both Medium and Strong Blue, I can definitely say that the lighting conditions make a huge difference in how white/bright it appears.

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Wow. Incredible article. Fig 6a is where I actually said WHOA out loud.

I really liked your solutions to the problem in the conclusion, too. I am kind of surprised that it's still not rectified. Is it just not a widely known issue?

ETA: As someone who has a stone that has been graded both Medium and Strong Blue, I can definitely say that the lighting conditions make a huge difference in how white/bright it appears.

It is a known issue, as evidenced by the 1998 statements by Martin Rapaport that are referenced at the front end of the article. But certainly not widely known at the consumer level. Even at the trade level there is not widespread awareness of the issue from what I can tell.

I agree with you Ame - it is surprising that the problem has not been rectified, especially considering how seemingly simple the solution is.

This begs the question of why it has not been conclusively addressed. And that is a bit of a head scratcher to me. The skeptic in me assumes that the reason is because manufactures benefit financially when diamonds are overgraded. But the author lays out the logical argument that correcting the grading issue would actually remove the stigma and reduce the discounting of fluoro stones. Accurately graded fluoro stones could then even potentially be sold for a premium with the presumption that their appearance would improve under some lighting conditions. And that would seem to be a bigger and more predictable benefit to the manufacturers.

And of course, it would simultaneously protect consumers.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

As I point out Bryan, the diamonds themselves will not allow any "solution" because there's too many variables in the stones themselves, to say nothing of the lighting issues.
The first "solution" would be to grade the diamonds face up- but even then, not all I colors will look alike.
Bottom line is that color, like clarity, must be assessed on a stone by stone basis.
I don't see any practical way around the physical limitation of the diamonds themselves.
Consumers are best protected by selecting a seller who can properly answer the questions on any given specific stone being offered.

Nor is this a given to be benefiting the manufacturers- as it can work both ways. Color grading is just not possible to calibrate in a more scientific manner than we have now IMO

 

[queradas]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Michael Cowling from Accredited Gemologist Association (AGA) Certified Gem Laboratory has put together an article about blue fluorescent diamond over grading.

https://www.pricescope.com/journal/blue-fluorescent-diamonds-color-grading-issues

Thank you Michael.

Thank-you for an interesting read and history about grading and fluorescence. I would agree with the authors proposed simplest solution to use filters or diffusers to filter out UV as was intended by GIA's unfortunately poor choice of light in the 90s. Why it hasn't been done likely lies in how hard it is for trade and GIA-GTL to make any changes to the way they have done grading or to admit that there is a better way and then spend money to change and standardize a new grading environment. I suspect for the GIA diamond dock, adding filters is a quick and easy fix.

I am not sure what "equipment" or model Garry H is trying to propose but the counter approach to this is to try to better model lighting with UV to represent a grading environment that better approximates "natural" lighting. I think this is the wrong way to go as it won't approximate artificial lighting as well and it won't be easy to model or agree on the appropriate amount and type of UV containing light or to standardize a grading environment containing UV.

A red herring to this issue is grading faceup versus crown down. I see this as irrelevant and detrimental to the issue and the same reasons D-Z diamonds are graded face down doesn't change when one factors in Fluorescence. Separating the color differences attributed solely to cut in the faceup position amongst diamonds graded the same color facedown as a result of different cut versus the effects of only fluorescence makes this issue more complicated than it needs to be.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

I'm sure that a better theoretical model might be made. But I agree with ,,Garry- GIA has a reasonable approach given that we are not dealing with theoretical diamonds. As such the face up appearance is at the crux of what we are calling "over grading".
It's og only cut that will make two diamonds of the same color grade face up differently. There's differences in the material itself.
Bottom line is that a system that allows for there inconsistencies is what we have now. And it works.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Here's where the conclusions of the article are off base.

Conclusions:
Nearly two decades have passed, and the problem remains due to the almost universal use of fluorescent lighting in diamond color grading. The result is continuing distrust of blue fluorescent diamonds with the consequent discounting required to sell them.

From Wade’s time to this day gemologists and the trade refer to the diamond’s color unimproved by fluorescence as its “true color.” It is the color commonly seen in a diamond at typical viewing distances from artificial illumination at night or indoors out of daylight. There the light at the diamond contains insufficient UV (less than one microwatt) to stimulate grade whitening fluorescence.
Trying to color grade diamonds in insufficient, night time, or dim lighting is just not possible. Daylight has been used forever and for good reason. You're going to need a fair amount of light to distinguish a D from an E ie

Restoration of grading for the diamond’s true color can be accomplished by the use of polycarbonate plastic such as Lexan. Polycarbonate is an effective and inexpensive filter that blocks the UV in fluorescent lighting, removing its grade whitening effect on blue fluorescent diamonds. Another solution is the use of white LED technology. LED lighting provides inherently UV-free grading light avoiding noticable stimulation of fluorescence.

Either solution is consistent with the trade’s historical desire that diamonds be examined for their unenhanced “true body color” in lighting largely free of UV.
I don't agree that there's a "historical desire" to color grade in UV free lighting. At Harry Winston all color grading was done in the morning. This was in 1976 when Harry Winston was undisputed as the largest loose diamond dealer in the world.

A return to the practice of grading a diamond’s true color rather than its fluorescence enhanced color would benefit the diamond industry in several ways.

First it would remove the distrust and stigma attached to fluorescent diamonds.

Second, the rarer blue-fluorescent diamonds that hold their high-white color in the absence of fluorescence stimulating UV and VV would be recognized for their superior beauty and rarity to diamonds that drop in color.

Thirdly, blue-fluorescent diamonds could be shown to whiten from their graded color, and sometimes appear blue-white in natural daylight. Promoting this advantage in comparison with non-fluorescent diamonds of similar grade would return the marketing advantage to blue fluorescent diamonds that they once enjoyed.
Here we agree- just extend "natural daylight" to "lighting bright enough to determine small differences in color grade"

By grading in lighting that does not stimulate fluorescence, fairness and consistency can be achieved, restoring trust in and rekindling desire for this outstanding gemstone.

Given that we agree that MB or SB diamonds will "color shift" based on lighting, at the end of the day, all we can do is come up with a compromise in the lighting used in color grading- as no single source is going to represent real life.
That's pretty much what we have right now.
In the case of Yellow diamond the problem is far worse by the way.
Bottom line is that any color grade is simply a guide- specific stones need to be judged on their own merits.

 

[michaelgem]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Thanks to everyone for the lively discussion of this issue. It’s of importance to the trade and of even more importance to the consumer.

Rather than reflecting my opinion, this article is a reporting of diamond industry grading practice and GIA teaching from its founding in 1931 through the mid 1990’s. GIA’s teaching and grading practice reflected and systematized diamond industry grading practices and knowledge. I’m a messenger to the consumer similar in a way to Indianapolis chemistry teacher, Frank Wade in the early 20th century: “Wade was a pioneer in America of “the first series of scientific articles (from 1915 to 194 on diamonds and gems written especially for the jeweler” [Gilbertson, A., 2007]

Were it not for Wade’s reporting in 1915 in “Diamonds” (brought to light by Al Gilbertson) we would lack proof that this grading issue of blue fluorescent diamonds and its resolution goes back in the trade to at least 1900.

The comments and questions recently posted here are addressed to various degrees in each of three articles, the second of which is this contribution to Pricescope. The most detailed reporting is contained in the Journal of Gemmology study article Cowing, M.D., 2010. “The overgrading of blue fluorescent diamonds: the problem, the proof and the solutions”, The Journal of Gemmology, vol. 32/Nos 1-4, 38-51.

In posts to follow I’ll refer to the relevant sections of this work, which can be downloaded at http://www.acagemlab.com/temp/CowingOvergrading.pdf..

Bryan Boyne’s postings indicate a thorough reading and understanding of this pier reviewed article. He is an example illustrating that a thorough read can result in complete understanding of this issue and its solution for the betterment of the diamond trade and the consumer.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

HI Michael- It's great that we can finally discuss the specifics of this article. Bryan does agree with the conclusions, but he's by no means the only one who has read and understands that article, as well as your conclusions about overgrading.
Understanding the article and agreeing with the conclusions are two separate issues. Ironically, I do believe we all agree that MB or SB stones are not inherently problematic, and are therefore discounted unfairly.
We're all here to forward consumer education. In my opinion the conclusions of the article go against that end.


In my post below I raise a few specific points that I would appreciate you addressing:

Here's where the conclusions of the article are off base.

Conclusions:
Nearly two decades have passed, and the problem remains due to the almost universal use of fluorescent lighting in diamond color grading. The result is continuing distrust of blue fluorescent diamonds with the consequent discounting required to sell them.

From Wade’s time to this day gemologists and the trade refer to the diamond’s color unimproved by fluorescence as its “true color.” It is the color commonly seen in a diamond at typical viewing distances from artificial illumination at night or indoors out of daylight. There the light at the diamond contains insufficient UV (less than one microwatt) to stimulate grade whitening fluorescence.
Trying to color grade diamonds in insufficient, night time, or dim lighting is just not possible. Daylight has been used forever and for good reason. You're going to need a fair amount of light to distinguish a D from an E ie

Restoration of grading for the diamond’s true color can be accomplished by the use of polycarbonate plastic such as Lexan. Polycarbonate is an effective and inexpensive filter that blocks the UV in fluorescent lighting, removing its grade whitening effect on blue fluorescent diamonds. Another solution is the use of white LED technology. LED lighting provides inherently UV-free grading light avoiding noticable stimulation of fluorescence.

Either solution is consistent with the trade’s historical desire that diamonds be examined for their unenhanced “true body color” in lighting largely free of UV.
I don't agree that there's a "historical desire" to color grade in UV free lighting. At Harry Winston all color grading was done in the morning. This was in 1976 when Harry Winston was undisputed as the largest loose diamond dealer in the world.

A return to the practice of grading a diamond’s true color rather than its fluorescence enhanced color would benefit the diamond industry in several ways.

First it would remove the distrust and stigma attached to fluorescent diamonds.

Second, the rarer blue-fluorescent diamonds that hold their high-white color in the absence of fluorescence stimulating UV and VV would be recognized for their superior beauty and rarity to diamonds that drop in color.

Thirdly, blue-fluorescent diamonds could be shown to whiten from their graded color, and sometimes appear blue-white in natural daylight. Promoting this advantage in comparison with non-fluorescent diamonds of similar grade would return the marketing advantage to blue fluorescent diamonds that they once enjoyed.
Here we agree- just extend "natural daylight" to "lighting bright enough to determine small differences in color grade"

By grading in lighting that does not stimulate fluorescence, fairness and consistency can be achieved, restoring trust in and rekindling desire for this outstanding gemstone.

Given that we agree that MB or SB diamonds will "color shift" based on lighting, at the end of the day, all we can do is come up with a compromise in the lighting used in color grading- as no single source is going to represent real life.
That's pretty much what we have right now.
In the case of Yellow diamond the problem is far worse by the way.
Bottom line is that any color grade is simply a guide- specific stones need to be judged on their own merits.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Michael, Re-thinking what you've term "historical desire"- I can see that we are considering a different context to the term.
Your point about this discussion going back to Wade's reporting would indeed indicate something"historical"

My point is that the lighting under which the diamonds were looked at, as well as many other factors, brought tremendous changes to the trade between 1915 and the present day. Current thinking in the market is not really related to 70 - 100 years ago.
My point better put would be that maybe there was a historical desire that diamonds be examined for their unenhanced “true body color” in lighting largely free of UV. But speaking from a historical period from the late '70's to today I have not seen such an desire from traders.
Gem labs may operate in dark field, but trading floors are generally well lit, and include daylight. Since the '70's anyway.

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

It seems to me to be a pretty straight forward issue. Based upon the science and historical perspective presented in the 2010 study, which I have not seen disputed, diamonds are being graded today in a lighting environment that allows for varying degrees of temporary color masking due to fluorescence. This naturally leads to systematic over-grading of color.

From the earliest days of gemology, as the author explains, this issue has been known and grading practices developed so that the “true color” of the diamond was observed by the grader. This practice was designed to promote grading consistency and accuracy and to protect the consumer from purchasing a diamond that would not look as white under typical viewing conditions as its lab grade would indicate.

These historical safeguards have apparently been abandoned by the labs in modern times, and evidence presented in the 2010 study (and corroborated-if unintentionally- by photographs in the GIA survey), demonstrate fairly dramatically the extent of the current problem.

The effect on market prices due to the over-grading of blue fluorescent diamonds was clearly articulated by Martin Rapaport, one of the diamond trade’s most influential participants. Indeed the person who probably knows more about that diamond market than anyone on earth.

Fortunately, the solution to returning to historical grading consistency and accuracy is quite simple. The grading environment can be altered to exclude excitation of color masking fluorescence by a combination one or more of the following; filtration, diffusion, or increasing distance from the light source.

While lab practices and trade practices might be more or less in line in terms of looking at diamonds in environments with varying degrees of fluorescence stimulating UV (diamond dock, fluorescent desk lamps, north daylight) , normal viewing environments do not afford the consumer the benefit of color masking. So from a consumer protection standpoint, which is the avowed mission of the GIA and other top tier labs, this issue should be corrected or conclusively addressed.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

I, and others have disputed the science behind the assumptions Bryan, so clearly it's not "undisputed"
Again at the crux of the issue, how much does a given MB or SB stone change when exposed to different lighting environments.
There's not only no science to "prove" some stones don't have beneficial effects from fluorescence, the study seems to back up the fact that some MB/SB diamonds have visible color change.

Thirdly, blue-fluorescent diamonds could be shown to whiten from their graded color, and sometimes appear blue-white in natural daylight.

What is "natural daylight" and how does it ( whatever we are agreeing that it is) differ from the light consumers view diamonds under?
There' no proof that some diamonds do not react to other spectra, and there's also no proof of how much UV, or VV is in any given lighting environment.
This does not sound very clinical or scientific to me- and of course real life experience with countless real life diamonds has proven to me beyond a doubt that some MB or SB near colorless stones have easily visible benefits in terms of face up color improvement.

I'd be interested in what Martin Rappaport had to say, and the context thereof- but I would also point out that he is by no means the "last word" in diamond trading.

How does this all affect consumers?
Isn't that the crux of the entire issue?

I speak to many thousands of consumers, and they have a lot of questions.
So would I if I was buying such an expensive item and I was not an expert on the subtle aspects.
It's very convenient for sellers to answer questions with definitive "pat" answers. ( I'm not referring to anyone involved in this discussion) The problem is that there's no simple answers regarding fluorescence.
No simple answer on it's effect on the buying and selling of diamonds, nor about the physical realities of how fluorescence works.
This extends to discussions of how we grade the color.
By no means am I a blanket apologist for trade practices- just the opposite. I strive for transparency.
But in my opinion there's nothing "sinister" about how GIA color grades diamonds.
It's a well established compromise.
Given the limitation of grading diamonds, I think it's probably as good as we can hope for

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

The whole point of a laboratory report is to render an objective analysis of a diamond as accurately and consistently as possible so that consumers can make the most informed buying decisions possible.

If there is a variable being introduced to the grading process that diminishes consistency or accuracy in grading, especially one that has been known to do just that for over 100 years, then it is only logical that it should be corrected, if at all possible.

Precautions were historically taken to prevent inaccuracy of color grading due to the effects of fluorescence. Grading practices appear to have changed removing those precautions. Yet, I don't think our need for accuracy is any less today. With more and more people buying online and depending heavily on lab reports, I would argue that our need for accuracy is even greater today.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Bryan, the purpose of a GIA report, and it's actual utility may be two different things.

In my opinion, the grading was set up in a manner that is in some ways, clinical. But the grades leave a lot open to interpretation.
For example, is an SI1 eye clean?
GIA grades the presence of imperfection, as opposed to it's visibility in the diamond. Yet visibility is probably the more important aspect for a consumer.
We have the GIA cut grade- of course only for round diamonds.
That would seem to achieve the goal of a "buy it blind" cert for consumers.
But of course if you read PS for a few minutes you'll find that the GIA cut grade is not accepted as a "buy it blind" document by knowledgeable consumers.
Same holds true for color.
Does a J face yellow?
Sometimes.
Why can't GIA just give us the answers!!

Simple. As I've pointed out repeatedly, there's huge variances from one stone to the next that must be taken as a whole. Bottom line is that the culmination of all these factors combine to form a stones's desirability, and ultimately price.

Fluorescence is squarely in this category.
We can identify it on a GIA report, but we can not really determine fluorescence's effects on the diamond from the GIA.

 

[queradas]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

If there is a variable being introduced to the grading process that diminishes consistency or accuracy in grading, especially one that has been known to do just that for over 100 years, then it is only logical that it should be corrected, if at all possible.

There is precision(consistency) and accuracy, these are two different things.
Putting on a Lexan filter(UV) as Michael suggested in his paper certainly would improve precision, it would not matter how close the tray was to the lights, the amount or type of fluoro would no longer be a variable, they would be negligible. Color Grading would become more consistent or precise.

However would it make the result more accurate?

Accuracy is how close the measurement is to a known value or the correct value.

That would depend on the goal of color grading.

1) If its to determine rarity and thus price based on body color alone independent of fluorescence? (Yes I believe it would).
2) To report a body color from a known set of standards so those familiar with the standards would know how much body tint this diamond has in the usual customer lighting environments? (Maybe not).

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

If there is a variable being introduced to the grading process that diminishes consistency or accuracy in grading, especially one that has been known to do just that for over 100 years, then it is only logical that it should be corrected, if at all possible.

There is precision(consistency) and accuracy, these are two different things.
Putting on a Lexan filter(UV) as Michael suggested in his paper certainly would improve precision, it would not matter how close the tray was to the lights, the amount or type of fluoro would no longer be a variable, they would be negligible. Color Grading would become more consistent or precise.

However would it make the result more accurate?

Accuracy is how close the measurement is to a known value or the correct value.

That would depend on the goal of color grading.

1) If its to determine rarity and thus price based on body color alone independent of fluorescence? (Yes I believe it would).
2) To report a body color from a known set of standards so those familiar with the standards would know how much body tint this diamond has in the usual customer lighting environments? (Maybe not).

That is a valid point queradas. The accuracy would be in how close the human graders get to the known value which is determined by comparison with master sets, which are by prescription all non-fluorescent.

There will still be the human element in grading which should be +- one grade. It just would not be complicated by fluorescent whitening, thereby making it more consistent.

There would still be influences on apparent color by shape, facet arrangement, and cut quality. These would be in the realm of buyers preference, and for the buyer to determine based upon other diagnostics and ultimately personal inspection. But to the extent that true body color is reported by the lab more accurately, they have a more reliable baseline to work from.

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

The whole point of a laboratory report is to render an objective analysis of a diamond as accurately and consistently as possible so that consumers can make the most informed buying decisions possible.

If there is a variable being introduced to the grading process that diminishes consistency or accuracy in grading, especially one that has been known to do just that for over 100 years, then it is only logical that it should be corrected, if at all possible.

Precautions were historically taken to prevent inaccuracy of color grading due to the effects of fluorescence. Grading practices appear to have changed removing those precautions. Yet, I don't think our need for accuracy is any less today. With more and more people buying online and depending heavily on lab reports, I would argue that our need for accuracy is even greater today.

Bryan very little of what labs do is objective or helpful to consumers making buying decisions.
e.g.
Grading diamond color from pavilion side when we all know cut shapes and quality make big face up changes
Grading clarity by inclusion size for high clarity and inclusion coverage in lower clarity grades which means VS2 is eye visible in 10ct size and I1 is invisible in melee.

I agree with David that in my experience GIA & AGS have their lighting right now (and they found a better use for Diamond Dock).

Michael's article is full of holes which I am running out of time to address before Hong Kong trade show.
Would anyone like to answer a simple question?

Find a light level can you see the difference between say 1ct round H and F face up in a ring? If you can see a difference in 2 non fluoro stones, what if the H was strong blue fluoro and the same level of light that is good enough to see a difference (and is not totally UV or VV free, like LED) - would there be an apparent improvement and make it harder to tell if there was a difference?

I have asked Michael that question face to face and never got a straight answer.

 

[queradas]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Thanks to everyone for the lively discussion of this issue. It’s of importance to the trade and of even more importance to the consumer.

Rather than reflecting my opinion, this article is a reporting of diamond industry grading practice and GIA teaching from its founding in 1931 through the mid 1990’s.

No Michael your response has done the opposite and your opinion in the paper is obvious. Bryan "gets it" because he echoes your conclusion which is that GIA should make a change and remove UV containing light from their color grading environment.

But they won't and here is why:

"To ensure consistency in GIA’s grading, proposed changes in lighting must be thoroughly tested to balance the potential benefits to the grading methodology against the very real damage that would be caused if subsequent color grades were inconsistent with earlier ones. (The success the laboratory has had in this regard can be tracked in very real terms through its update service. Today we occasionally see diamonds graded in the 1970s that have been submitted for updated grading reports; after they have undergone a full grading process using contemporary equipment and procedures, the vast majority are returned with the same grade determinations."

In short, it could draw into question the grading of every Strong Blue Fluoro Diamond (Maybe Medium as well) on resubmit. How many are there? How many would get color grade adjustments downwards which obviously no trade would be willing to readily resubmit?

Here is also there 2008(I think current) position:

“Yes, you can create an environment devoid of UV but it’s a false situation . . . . It may sound like the ideal, but it steps
outside the practical world. It’s not relevant because it doesn’t really exist anywhere. We try to be sensitive to the practical gemological issues.”

"Tom Moses corroborated this position at GIA by stating, “We found that the Verilux bulbs used in GIA’s diamond grading
units, standard cool-white fluorescent light bulbs, and northern hemisphere daylight (even filtered through a glass window) all have a certain amount of UV radiation. Hence the Verilux sources are similar—in terms of UV exposure—to grading environments throughout the world”

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Thanks to everyone for the lively discussion of this issue. It’s of importance to the trade and of even more importance to the consumer.

Rather than reflecting my opinion, this article is a reporting of diamond industry grading practice and GIA teaching from its founding in 1931 through the mid 1990’s.

No Michael your response has done the opposite and your opinion in the paper is obvious. Bryan "gets it" because he echoes your conclusion which is that GIA should make a change and remove UV containing light from their color grading environment.

But they won't and here is why:

"To ensure consistency in GIA’s grading, proposed changes in lighting must be thoroughly tested to balance the potential benefits to the grading methodology against the very real damage that would be caused if subsequent color grades were inconsistent with earlier ones. (The success the laboratory has had in this regard can be tracked in very real terms through its update service. Today we occasionally see diamonds graded in the 1970s that have been submitted for updated grading reports; after they have undergone a full grading process using contemporary equipment and procedures, the vast majority are returned with the same grade determinations."

In short, it could draw into question the grading of every Strong Blue Fluoro Diamond (Maybe Medium as well) on resubmit. How many are there? How many would get color grade adjustments downwards which obviously no trade would be willing to readily resubmit?

Here is also there 2008(I think current) position:

“Yes, you can create an environment devoid of UV but it’s a false situation . . . . It may sound like the ideal, but it steps
outside the practical world. It’s not relevant because it doesn’t really exist anywhere. We try to be sensitive to the practical gemological issues.”

"Tom Moses corroborated this position at GIA by stating, “We found that the Verilux bulbs used in GIA’s diamond grading
units, standard cool-white fluorescent light bulbs, and northern hemisphere daylight (even filtered through a glass window) all have a certain amount of UV radiation. Hence the Verilux sources are similar—in terms of UV exposure—to grading environments throughout the world”

I understand the political reasons that labs would resist a grading change. (which again begs the question of why they departed from their historical practice in the first place).

And it does not appear to be necessary to eliminate all UV or VV from the grading environment. The point is to eliminate temporary grade altering whitening from taking place during grading process. And according to the science presented in the article, that can be achieved by increasing the distance between light source and point of observation.

The data presented indicates that UV intensities sufficient to stimulate grade whitening fluorescence are achieved (with respect to artificial light sources) only when the diamond is held at very close range to the source. Which happens to be the practice at the labs and at diamond dealers desks all over the world.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Bryan, the "data" or "science" in this article is totally insufficient to make any sort of conclusions about how much UV s present, and or needed to improve the color of fl stones.
I don't understand why we can't get past this point.
Either there's sufficient UV, or VV in normal room lighting which is bright enough to distinguish small color differences to stimulate color change in some SB, or MB stones- or other factors achieve this goal. This is a physical reality observed by pretty much anyone who looks at a lot of fl diamonds.
GIA's own statements back this up. Not that we need any sort of statement or documentation to confirm what our eyes clearly see.
About a change from historical practices, there's been so many changes to lighting technology, as well as gemological tools over the past 30 years, it would make no sense for GIA to ignore all that.
There's nothing whatsoever "sinister" about this.
And above all, it works very well.
Regardless of whatever Rappaport says, the market has a way of allowing for these inconsistencies.
To prove this point do a search for a 1.00 G/SI1 triple EX on your site, or any other one which has a link to the "virtual" diamond database.
You'll find a variance of up to double from the cheapest to most expensive stones. You'll notice large differences in price from one MB stone to the next.
MB or SB stones showing detrimental haziness are offered at a fraction of an SB stone which is not hazy.

So in the end it all works pretty well.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Thanks to everyone for the lively discussion of this issue. It’s of importance to the trade and of even more importance to the consumer.

Rather than reflecting my opinion, this article is a reporting of diamond industry grading practice and GIA teaching from its founding in 1931 through the mid 1990’s.

No Michael your response has done the opposite and your opinion in the paper is obvious. Bryan "gets it" because he echoes your conclusion which is that GIA should make a change and remove UV containing light from their color grading environment.

But they won't and here is why:

"To ensure consistency in GIA’s grading, proposed changes in lighting must be thoroughly tested to balance the potential benefits to the grading methodology against the very real damage that would be caused if subsequent color grades were inconsistent with earlier ones. (The success the laboratory has had in this regard can be tracked in very real terms through its update service. Today we occasionally see diamonds graded in the 1970s that have been submitted for updated grading reports; after they have undergone a full grading process using contemporary equipment and procedures, the vast majority are returned with the same grade determinations."

In short, it could draw into question the grading of every Strong Blue Fluoro Diamond (Maybe Medium as well) on resubmit. How many are there? How many would get color grade adjustments downwards which obviously no trade would be willing to readily resubmit?

Here is also there 2008(I think current) position:

“Yes, you can create an environment devoid of UV but it’s a false situation . . . . It may sound like the ideal, but it steps
outside the practical world. It’s not relevant because it doesn’t really exist anywhere. We try to be sensitive to the practical gemological issues.”

"Tom Moses corroborated this position at GIA by stating, “We found that the Verilux bulbs used in GIA’s diamond grading
units, standard cool-white fluorescent light bulbs, and northern hemisphere daylight (even filtered through a glass window) all have a certain amount of UV radiation. Hence the Verilux sources are similar—in terms of UV exposure—to grading environments throughout the world”

Really great post and it raises some very important points- the author of this "study: is participating here, yet refuses to answer any of the considerations raised.
Bryan keeps citing this document, but there's some very real inconsistencies. If "peer review" is important, answering considerations raised by your peers would seem appropriate.

 

[michaelgem]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

There are many good points being raised by Bryan B (Texas Leaguer) (TL), Garry H (Cut Nut) (CN), Karl K, David F (Rockdiamond) and others. I settled on two dialogs, one between TL and CN, and one between Karl and Garry to respond, because they encompass elements of a lot of the discussion.

Dialog between Texas Leaguer (TL) and Garry H (Cut Nut) (CN)
"focus on the one with N3 mentioned - thats what causes fluoro in 99% of the diamonds we are discussing. Visible light is from just below 400nm to just above 700nm, UV to Infra red respectively. From those charts one can see that there is excitation occurring from the exact same blue frequency of the blue emission (as well as some other in the visible spectrum). That means that blue light with a frequency of 415nm cause blue excitation and makes a diamond look whiter whenever there is blue in the light spectrum. There are many different light types - some like halogens and tungsten don't make much blue light, but lots of others do. "CN

"One key issue as I understand it is that the mere presence of the wavelengths capable of exciting fluorescence is not adequate. They must be present in sufficient intensity. And intensity drops off very quickly with distance from indoor light sources, as demonstrated in detail in the 2010 study." TL

"Thanks Bryan - please see the connection - in order to see color differences or yellowishness, you need good light. You cannot tell the difference between a D and a L in a dimly lit restaurant. If you have enough light to pick a 1ct H from a D face up in a ring etc then you're going to have some radiation that will excite at least a small blue fluoro effect. The better and more light, the better your color acuity AND the better the blue fluoro assistance to washing away the yellow tint. " CN

"While the bolded part seems intuitive, it does not seem to be borne out by the science. It appears there is a level of intensity of the UV and VV wavelengths that must be achieved before significant excitation takes place. Therefore, you can have plenty of light to see by yet have no fluorescence-driven whitening taking place. " TL

Karl asks: "Do you know of any study that actually measured the UV light levels and wave lengths in common indoor lighting conditions both office and home?"

Garry says: "You will note that there is quite a lot of N3 blue excitation possible from visible frequency light - not just VV and invisible UV wavelength radiation. So, may I rest my case? That blue fluoro can and does improve face up color of many if not all strong blue fluoro diamonds in almost all lighting that is adequate to determine slight (1-2 grade) color differences. That means that blue light with a frequency of 415nm cause blue excitation and makes a diamond look whiter whenever there is blue in the light spectrum."

First, blue in the light spectrum does not excite blue fluorescence in a diamond.

Here are the ranges of wavelengths that produce the visual sensation of each color of the visible spectrum:
violet 380–450 nm 668–789 THz 2.75–3.26 eV
blue 450–495 nm 606–668 THz 2.50–2.75 eV
green 495–570 nm 526–606 THz 2.17–2.50 eV
yellow 570–590 nm 508–526 THz 2.10–2.17 eV
orange 590–620 nm 484–508 THz 2.00–2.10 eV
red 620–750 nm 400–484 THz 1.65–2.00 eV

No amount of blue (450–495 nm) in the light spectrum, no matter how intense, causes blue fluorescence in a diamond. Only the small part of the visible violet (VV) end of the visible spectrum at and below the N3 center at 415.2 can excite, along with UV, the blue fluorescence from the N3 aggregated nitrogen in Type 1A diamonds.

Thomas Hainschwang is a PhD and multidisciplinary gemologist who has specialized in diamonds and colored diamonds. He is currently carrying on advanced research on colored diamonds with major scientific organizations. For the AGA Task force on Lighting standards he generated the fluorescent response curves of the VSt Blue, 3.02ct diamond #5 in the 2010 study. These curves are representative of the fluorescence response of Type 1A diamonds to particular energy wavelengths of UV and VV.

They were obtained by exciting the diamond with near-monochromatic light in steps of 5 nm from 340 to 415 nm, produced from a Xenon light source via a monochromator. By this technique it is possible to excite fluorescence with any desired wavelength of the light source. The fluorescence was recorded for each excitation wavelength with a high sensitivity CCD spectrometer and the results normalized. Each recorded curve (in black) in Figure A represents fluorescence spectrum excited by the near-monochromatic light tuned to distinct wavelengths. To give an example, the first emission curve in Figure A represents the intensity of the fluorescence of the diamond when excited by near-monochromatic light with a central wavelength of 340 nm.

The 3D graph in Figure A thus shows the fluorescence intensity profile when the diamond is excited with such near-monochromatic light of various wavelengths.

These curves show what early diamond industry experts did not know, not just UV light, but also visible light up to 415 nm excites the blue fluorescence caused by the N3 centre (three nitrogen atoms surrounding a vacancy) in any diamond containing appreciable concentrations of A and B aggregates, and consequently N3 centers. As a result wavelengths up to 415 nm can be important contributors to blue fluorescence in Cape Series diamonds.

Note that the blue fluorescence response is greatest for UV excitation around 385nm (the pink peak) and falls to zero after 415.2nm

At normal viewing distances in typical strengths of artificial illumination (fluorescent overhead office lighting for example), where the "true color" is observed, the visible violet light intensity, just like the UV, was found to be too weak to excite noticeable fluorescence. But observation too close to either fluorescent or incandescent lighting such as occurs in the DiamondDock and DiamondLite, where the intensity exceeds about 400fc or 4000 lux, was found to excite grade whitening blue fluorescence (fc and lux are the units used in photometry as measures of visible light intensity, as perceived by the human eye.)

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Thanks for participating in a dialog Michael.
I have a question
What is the measuring device used to determine the intensity of the fluorescence in a given diamond- or to determine if the fluorescence is excited?

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Hi Michael,
We all call 415nm blue. We call the fluoro "blue fluorescence". I have never heard anyone say "violet" for N3 diamonds - have you?
I was never discussing light beyond +450nm. Ever.
Please be more careful.
Also refer to the email exchange and blue violet filtered light photo's I just took with my new 415nm filter. I have CC'd you that I have had with Thomas, who may not wish to be drawn in here.

 

[Karl_K]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Would anyone like to answer a simple question?

Find a light level can you see the difference between say 1ct round H and F face up in a ring? If you can see a difference in 2 non fluoro stones, what if the H was strong blue fluoro and the same level of light that is good enough to see a difference (and is not totally UV or VV free, like LED) - would there be an apparent improvement and make it harder to tell if there was a difference?

depends on the lighting and the diamond.
Is there enough uv in the wavelength the diamond responds strongly too for it to make a difference yes it should mask the body color.
This goes back to my friends wife's diamond which does not respond to some wavelengths but reacts very strongly to others.
That is why I think a test like you are talking about with a bunch of different wavelengths would be very interesting. Even more interesting would be the same test with hundreds(thousands) of diamonds of different lab ratings to find the outiers. Are diamonds like hers rare? Are there diamonds that show different colors based on wavelengths of the uv light?
There are so many different questions that come to my mind.

 

[michaelgem]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Would anyone like to answer a simple question?

Find a light level can you see the difference between say 1ct round H and F face up in a ring? If you can see a difference in 2 non fluoro stones, what if the H was strong blue fluoro and the same level of light that is good enough to see a difference (and is not totally UV or VV free, like LED) - would there be an apparent improvement and make it harder to tell if there was a difference?

depends on the lighting and the diamond.
Is there enough uv in the wavelength the diamond responds strongly too for it to make a difference yes it should mask the body color.
This goes back to my friends wife's diamond which does not respond to some wavelengths but reacts very strongly to others.
That is why I think a test like you are talking about with a bunch of different wavelengths would be very interesting. Even more interesting would be the same test with hundreds(thousands) of diamonds of different lab ratings to find the outiers. Are diamonds like hers rare? Are there diamonds that show different colors based on wavelengths of the uv light?
There are so many different questions that come to my mind.

Karl,

Re: That is why I think a test like you are talking about with a bunch of different wavelengths would be very interesting.

The fluorescent response curves of the VSt Blue, 3.02ct diamond #5 in the 2010 study is just the test you are talking about with a bunch of different wavelengths. These curves are representative of the fluorescence response of Type 1A diamonds to particular energy wavelengths of UV and VV.

Re: Even more interesting would be the same test with hundreds(thousands) of diamonds of different lab ratings to find the outliers. Are diamonds like hers rare?

The generally accepted data on gem quality white diamonds like your friend's wife's is that 98% are type 1A meaning they contain nitrogen aggregated in N3 centers in the crystal lattice, which results in the Cape Series tints of yellow and various degrees of blue fluorescence. The remaining 2% include type 2A, which lack readily detectable N3 nitrogen aggregation, and thus have no blue fluorescence.

This graph of response curves of a type 1A diamond from different wavelengths thus contains answers to your questions for perhaps 99 plus percent of white diamonds.

Re: Are there diamonds that show different colors based on wavelengths of the uv light?

The evidence is that fluorescence color due to N3 centers in Type 1A diamonds is similar for different wavelengths varying mainly in intensity. Notice that each of the curves has a similar shape with peaks in similar locations, and varies mainly in the amplitude of the response. Each wavelength thus produces a similar blue fluorescent color varying mainly in intensity.

These similar blue fluorescent colors of varying intensities are seen in the responses of the 25 Type 1A diamonds in the study data base. These diamonds were illuminated with long wave mercury vapor tubes which contain ionized-mercury-vapor peaks of blue-fluorescence-stimulating monochromatic energy at wavelengths of 365nm in the Ultra Violet and 405nm in the Visible Violet.

Those same fluorescence-stimulating mercury vapor peaks are present in all fluorescent tube lighting where they excite similar blue colors of grade whitening fluorescence like you see in these Type 1A study diamonds.

In a percentage of white diamonds other color centers may be present which would add fluorescence of some other type when stimulated with UV and VV, but that appears to be a low percentage. In that small percentage are white diamonds that fluoresce yellow, yellow-orange and rarely other colors such as green and red. All this is fortunate for the vast majority of diamonds in that the blue fluorescence of most all white diamonds is well understood and consequently can easily be taken into consideration in grading.

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Hi Michael,
We all call 415nm blue. We call the fluoro "blue fluorescence". I have never heard anyone say "violet" for N3 diamonds - have you?
I was never discussing light beyond +450nm. Ever.
Please be more careful.
Also refer to the email exchange and blue violet filtered light photo's I just took with my new 415nm filter. I have CC'd you that I have had with Thomas, who may not wish to be drawn in here.

I wish to correct myself.
After finding the magazine copy (rather than the online version) of Fluorescence Produced by Optical Defects in Diamonds, Yun Luo et al, G&G Summer 2013, I can see that the blue fluoro color we most commonly see in N3 diamonds is centered at 440nm, but in fact is in the visible range from 400nm (violet) to 500nm (the blue green boundary). That explains why the color we see is a powdery blue.

What is more revealing is that there is considerably more excitation caused by the 415nm visible violet light, light that generally surrounds us from many light sources, and it creates more excitation or intense blue fluorescence than the 365nm so called Long Wave UV which is all around us.

I have a 415nm filter just arrived for my camera, and when I take a photo with or without a sheet of Lexan, there is little of no difference. if anyone wants I will produce some.
If I had a Lux meter I could establish what amount of light is the minimum to enable a face up grade ability to differentiate between different colors face up unset, in jewellery, and table down.
Karl I do not think I will need any sub visible light UV LED's.
Can you, Bryan, or anyone else think of any experiments that I can conduct to prove Michael right and me wrong?