Article Over Grading of Blue Fluorescent Diamonds Revisited

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

HI Michael,
Will you please answer a simple question?
What device are you using to make your declarations about fluorescence in the few diamonds you are citing?
GIA uses human eyes to determine if a stone has fluorescence, and if so, the color and how much.
Have you got some sort of better system?

I have done actual testing on hundreds of thousands of diamonds- of course I had to use my eyes to do so- but if you can provide a better method, I'd be interested.

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

HI Michael,
Will you please answer a simple question?
What device are you using to make your declarations about fluorescence in the few diamonds you are citing?
GIA uses human eyes to determine if a stone has fluorescence, and if so, the color and how much.
Have you got some sort of better system?

I have done actual testing on hundreds of thousands of diamonds- of course I had to use my eyes to do so- but if you can provide a better method, I'd be interested.

If you are truly interested, you will find many of the answers to your questions contained in the study being discussed, as well in Michael's posts just above.
The methodology, equipment and results of the various measurements are specified in the article.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Thanks Bryan,
In the interest of uncovering the truth, if Michael is unwilling to do so, can you please identify which tools were used?
I can't see any reference to any sort of tool besides human eyes to be the final arbiter of the presence, degree, or color of fluorescence.
Obviously you've read and are defending the conclusions of this article so you must be familiar.

If we're only speaking of visual observation, it does put the conclusions in a different light.

 

[Texas Leaguer]

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?

Garry,
I am unclear on exactly what it is in the study that you find fault with (?). Therefore, I am not sure what it is you are trying to prove or disprove.

As to what additional experiments I would be interested in , they would involve better understanding the minimum intensity of UV/VV necessary to activate grade altering levels fluorescence, and the presence of those minimum levels in different lighting scenarios. To me that is one of the most interesting aspects of this study and one that bears not only on the grading issue but on the issue of under what circumstances blue fluorescence can or cannot have ANY practical effect on diamond appearance.

 

[Rockdiamond]

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?

Garry,
I am unclear on exactly what it is in the study that you find fault with (?). Therefore, I am not sure what it is you are trying to prove or disprove.

As to what additional experiments I would be interested in , they would involve better understanding the minimum intensity of UV/VV necessary to activate grade altering levels fluorescence, and the presence of those minimum levels in different lighting scenarios. To me that is one of the most interesting aspects of this study and one that bears not only on the grading issue but on the issue of under what circumstances blue fluorescence can or cannot have ANY practical effect on diamond appearance.

Hi Bryan,
What tools would you use if you could perform your experiment?
Clearly we're discussing the light, filters, etc. That part is really obvious. Once we've established the "correct" light- is there any device you know of which can measure visible fluorescence in a diamond?
This is a very simple question and at the core of the issue.

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Thanks Bryan,
In the interest of uncovering the truth, if Michael is unwilling to do so, can you please identify which tools were used?
I can't see any reference to any sort of tool besides human eyes to be the final arbiter of the presence, degree, or color of fluorescence.
Obviously you've read and are defending the conclusions of this article so you must be familiar.

If we're only speaking of visual observation, it does put the conclusions in a different light.

I have read the articles being discussed. The author does not seem at all to be unwilling to discuss the study or the conclusions. He is actively participating in the thread.

I think the conclusions derived from the study are quite logical based upon the information presented. And I have still not heard anyone challenge the science behind the study. I have heard strong objections to the study but nothing that I have found convincing.

And in liue of evidence invalidating the conclusions of the study, it surprises me to hear so many criticisms of the position that the labs could and should strive to mitigate a variable that is known to diminish grading accuracy.

Per your request to repeat information about tools used to measure fluorescence I would refer you to the side bar on the 3D chart by Thomas Hainschwang (figure A in the study).

 

[Texas Leaguer]

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?

Garry,
I am unclear on exactly what it is in the study that you find fault with (?). Therefore, I am not sure what it is you are trying to prove or disprove.

As to what additional experiments I would be interested in , they would involve better understanding the minimum intensity of UV/VV necessary to activate grade altering levels fluorescence, and the presence of those minimum levels in different lighting scenarios. To me that is one of the most interesting aspects of this study and one that bears not only on the grading issue but on the issue of under what circumstances blue fluorescence can or cannot have ANY practical effect on diamond appearance.

Hi Bryan,
What tools would you use if you could perform your experiment?
Clearly we're discussing the light, filters, etc. That part is really obvious. Once we've established the "correct" light- is there any device you know of which can measure visible fluorescence in a diamond?
This is a very simple question and at the core of the issue.

First let me make it clear that I am not a physicist! I am not even sure I just spelled that right. So a lot of this stuff is way over my pay grade. However, there clearly are spectrometers and other instruments for measuring levels of electromagetic radiation and the effects of different wavelengths and energy levels on various objects.

But I will have to leave it to others familiar with those instruments to design and conduct the experiments.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

There's no answer to my question in Figure A Bryan, and of course you know that.
What's clear is that you're unwilling to answer a very simple question- and obviously neither is Michael.
Again the question: What tools are used to measure the activation of fluorescence in a diamond. Since the two people here defending this flawed study refuse to answer, here it is: The answer is the human eye.

If there is information to back up that were NOT speaking of human observation, I can not find it- and your and Michael's tactic is to avoid a simple questions, instead responding with some sort of BS chart which does nothing to clarify the issue for the consumers and non physicists reading..
This aspect- the fact the entire theory is based on human observation- calls into question the results- which are clearly false.

Bryan, I happen to think you're a great contributor here on PS. And I'm sorry this particular issue brings us into conflict.
The issue is BELOW my pay grade, and has been for a long time - over 30 years of diamond buying.

I have to ask- if you're not really sure of how they're coming to these conclusions, you're no phyisist, by your own admission- why are you so stuck defending this flawed study?
The study is wroong Bryan

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

There's no answer to my question in Figure A Bryan, and of course you know that.
What's clear is that you're unwilling to answer a very simple question- and obviously neither is Michael.
Again the question: What tools are used to measure the activation of fluorescence in a diamond. Since the two people here defending this flawed study refuse to answer, here it is: The answer is the human eye.

If there is information to back up that were NOT speaking of human observation, I can not find it- and your and Michael's tactic is to avoid a simple questions, instead responding with some sort of BS chart which does nothing to clarify the issue for the consumers and non physicists reading..
This aspect- the fact the entire theory is based on human observation- calls into question the results- which are clearly false.

Bryan, I happen to think you're a great contributor here on PS. And I'm sorry this particular issue brings us into conflict.
The issue is BELOW my pay grade, and has been for a long time - over 30 years of diamond buying.

I have to ask- if you're not really sure of how they're coming to these conclusions, you're no phyisist, by your own admission- why are you so stuck defending this flawed study?
The study is wroong Bryan

From Figure A "The fluorescence was recorded for each excitation wavelength with a high sensitivity CCD spectrometer"

David, human observation is a part of the study. It is a group of samples with varying degrees of fluorescence and human applied lab grades that are the subject of the article.

Simply repeating how much a study is "wrong" does not make it so. No matter how aggressively you press the point.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Bryan- say I found a study that claims pigs can fly. One probably does exist somewhere
We'd need to understand how these pigs were getting off the ground.
The aspects of the study which don't jibe with physical reality need to be clarified.
If we're using a slingshot, we can certainly get those pigs off the ground.

If a bacon company was using selling these as "flying bacon pigs" we'd call the validity of the study into question. To do so, as people familiar with bacon, we'd need to know what methods were used to get those pigs in the air.
We should not need to be pilots to understand pigs don't fly.

If there are tools being used, and the results being produced by these tools are being questioned, we need far more information about exactly how these tools are being used.

To continue with the analogy- when questioned how the pigs fly, the defenders of the study won't answer, but instead will pull out an aerodynamic chart showing how far a pig can fly.
References to "major scientific organizations" yes that means a lot.
Diversion tactics.

But pigs still can't fly, and certain MB/SB stones DO show color improvement in the vast majority of lighting bright enough to allow the human eye to observe slight differences in color.
This is true no matter how many times anyone says it's not.

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Bryan- say I found a study that claims pigs can fly. One probably does exist somewhere
We'd need to understand how these pigs were getting off the ground.
The aspects of the study which don't jibe with physical reality need to be clarified.
If we're using a slingshot, we can certainly get those pigs off the ground.

If a bacon company was using selling these as "flying bacon pigs" we'd call the validity of the study into question. To do so, as people familiar with bacon, we'd need to know what methods were used to get those pigs in the air.
We should not need to be pilots to understand pigs don't fly.

If there are tools being used, and the results being produced by these tools are being questioned, we need far more information about exactly how these tools are being used.

To continue with the analogy- when questioned how the pigs fly, the defenders of the study won't answer, but instead will pull out an aerodynamic chart showing how far a pig can fly.
References to "major scientific organizations" yes that means a lot.
Diversion tactics.

But pigs still can't fly, and certain MB/SB stones DO show color improvement in the vast majority of lighting bright enough to allow the human eye to observe slight differences in color.
This is true no matter how many times anyone says it's not.

Really David? Do you really think the flying pigs analogy is additive to the discussion?

I think it would really help the discussion of the topic of this thread, which is a specific article, if we would stick to analyzing the substance and conclusions of the article.

I honestly do not know with any specificity what exactly you are critiquing about the study. Is it the methodology, the instrumentation, the measurements, a flawed understanding of the physics of light, or conclusions that are not born out by the data collected?

My guess is that you are objecting to the study because the data are not consistent with your statement above : "certain MB/SB stones DO show color improvement in the vast majority of lighting bright enough to allow the human eye to observe slight differences in color."

While the findings of this study suggest that would not generally be the case (not sure what you mean by "certain MB/SB stones") , I would think the question could be answered by scientific experimentation. And that is exactly what I suggested in response to Garry's question.

Perhaps Mr. Cowing and/or his colleagues could expand on the study to address this broader question.

 

[michaelgem]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

HI Michael,
Will you please answer a simple question?
What device are you using to make your declarations about fluorescence in the few diamonds you are citing?
GIA uses human eyes to determine if a stone has fluorescence, and if so, the color and how much.
Have you got some sort of better system?

I have done actual testing on hundreds of thousands of diamonds- of course I had to use my eyes to do so- but if you can provide a better method, I'd be interested.

David,

You are raising an interesting topic, one I recently had occasion to discuss with two GIA Gem Trade Labs diamond graders, as well as recently retired AGSL director Peter Yantzer.

Up until recently both GIA and AGSL employed a set of master blue fluorescent diamonds that were on the borders between none, faint, medium, strong and very strong. This should have worked fine, as even though the blue emission strength varies with distance and type of UV excitation, both the unknown and the masters vary together allowing correct visual fluorescent grading.

However, with all your experience you surely know that fluorescence grading on lab reports is often way off, and for no good reason that I can see given that the grader has master diamonds against which to compare.

Recently, GIA has taken the human vision element out of fluorescence grading with an instrument that measures the fluorescence strength and reads out the call digitally, no human vision involved.

Just my opinion, but I see problems in taking human perception of fluorescent strength and color out of the equation, but that is another topic altogether.

It's interesting to look at the variation in each row of the diamonds of each fluorescence grade in the 25 diamond, study data base. The fluorescence grade call of these diamonds was made by GIA. Note that the rows of Medium and Strong Blue are fairly consistent, but there is a much greater variation in the row whose stones were graded by GIA as Very Strong Blue. One has fluorescence strength similar to the row of Strong Blues, while the two marquises and the pear appear much stronger.

If the labs photographed the diamond being graded along with the masters in long wave UV, as was done here, it would be hard to argue with the call, as the position among the masters would be as obvious as the fluorescent strength variation in this data-base photo.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Thanks you so much for the direct answer Michael.
I did speak with GIA today, and they are pretty cagey- but they did repeatedly state that fluorescence grading is done via human observation.
I am not doubting your statement that they are using a machine- but if so, what is that instrument?

I do agree that there's a lot of inconsistency in GIA FL grades.
I am a big supporter of GIA ( which is the "best of the worst")- but I have encountered multiple errors in FL grading over the past two years.
The errors we've experienced were not really a "judgment" calls- rather human error. For example calling a MB stone inert.
Your suggestion of a picture is a very good one.
Not that I believe GIA will alter it's methods because of this discussion- but it's still a great idea.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Bryan, rather than dredge up quotes, I will re-phrase my main point of contention with the study simply:
I have observed- on may occasions, stones of near colorless grading- H-I-J-K, which exhibit grade whitening appearance. They look one color through the pavilion, and another ( improved) color face up.
I have noticed this in many different lighting environments.
The study claims there's insufficient UV present to achieve this- you and I have disagreed on multiple occasions, based on you citing this study.

Since I ( and others) have observed this "whitening" phenomena - and on many occasions, I question the claim of the study.
If the study is using human observers to back up the claim, that does not immediately invalidate it- but it does lead to many more questions. How many human observations? Under what specific lighting environment? What was the number of diamonds were tested? What were the specifics of the diamonds tested?
If the study used tools to make the claims, we need to understand what tools were used, and in what conditions.

I am VERY interested in presenting the correct facts to the members of this forum. I know you are too.

That's why I qualified my statement: Certain MB/SB stones possess this grade whitening effect- but by no means all. There's so many reasons possible for this inconsistency. I do not want to become a physisst ( or however you spell it) but I would love to learn why some stones do whiten face up, and others don't.
So I can't say why, but based on literally hundreds of thousands of observations, I can say some do and some don't.
I think we all agree that most MB/SB stones are fine- a small percentage exhibit obvious dullness.
That would seem to back up my experience that it's just not a consistent phonomina

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Thanks you so much for the direct answer Michael.
I did speak with GIA today, and they are pretty cagey- but they did repeatedly state that fluorescence grading is done via human observation.
I am not doubting your statement that they are using a machine- but if so, what is that instrument?

I do agree that there's a lot of inconsistency in GIA FL grades.
I am a big supporter of GIA ( which is the "best of the worst")- but I have encountered multiple errors in FL grading over the past two years.
The errors we've experienced were not really a "judgment" calls- rather human error. For example calling a MB stone inert.
Your suggestion of a picture is a very good one.
Not that I believe GIA will alter it's methods because of this discussion- but it's still a great idea.

The article I have referenced from GIA G&G journal Summer 2013 explains that there are many reasons why the same UV instrument can give different results based on age of UV tubes - let alone different devices and different levels of excitation and distances from source.

(I would throw in that different cuts also play a role - note how the crush ice parts of fancy cuts concentrate the Fluoro effect).

I have no problem with instrumental measurement - but would much prefer GIA reveal the methodology. My guess is they do not because they want to reduce their labour costs base compared to competitor labs.

 

[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?

Garry,
I am unclear on exactly what it is in the study that you find fault with (?). Therefore, I am not sure what it is you are trying to prove or disprove.

As to what additional experiments I would be interested in , they would involve better understanding the minimum intensity of UV/VV necessary to activate grade altering levels fluorescence, and the presence of those minimum levels in different lighting scenarios. To me that is one of the most interesting aspects of this study and one that bears not only on the grading issue but on the issue of under what circumstances blue fluorescence can or cannot have ANY practical effect on diamond appearance.

Yes Bryan, I agree. But I also wish to add this part: We need to be able to understand what level of lighting is reasonable for people to be able to actually tell the difference between different color grades. So this means identifying say 2 or more Type Ia N3 diamonds of similar cut and with reasonably different grades (to be decided), with one or more inert and one or more with typical Strong Blue fluoro. Medium Blues could also be used, as could Very Strong blues.
I imagine a study would involve experts (as consumers may need too much training) and should be focused on face up rather than table down grading in various types of lighting that have been determined to make grade distinctions just possible - so the grades may need to be 2 apart, or in the case of top colors - D and F?
It is possible to make a big study of a dozen or more stones.
Perhaps we could arrange something for Vegas?

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Thanks you so much for the direct answer Michael.
I did speak with GIA today, and they are pretty cagey- but they did repeatedly state that fluorescence grading is done via human observation.
I am not doubting your statement that they are using a machine- but if so, what is that instrument?

I do agree that there's a lot of inconsistency in GIA FL grades.
I am a big supporter of GIA ( which is the "best of the worst")- but I have encountered multiple errors in FL grading over the past two years.
The errors we've experienced were not really a "judgment" calls- rather human error. For example calling a MB stone inert.
Your suggestion of a picture is a very good one.
Not that I believe GIA will alter it's methods because of this discussion- but it's still a great idea.

The article I have referenced from GIA G&G journal Summer 2013 explains that there are many reasons why the same UV instrument can give different results based on age of UV tubes - let alone different devices and different levels of excitation and distances from source.

(I would throw in that different cuts also play a role - note how the crush ice parts of fancy cuts concentrate the Fluoro effect).

I have no problem with instrumental measurement - but would much prefer GIA reveal the methodology. My guess is they do not because they want to reduce their labour costs base compared to competitor labs.

Yes, I am sure that GIA are constantly looking for ways to improve efficiency in the grading process, especially considering their expansion and their significantly increased volume. They are aparently doing some color grading of certain small stones exclusively by machine today. And I think it would be very interesting to know more about how they are approaching fluorescence reporting with instrumentation.

And really, all the discussion about which wavelengths activate fluoro and what colors and strengths of fluorescesce results under a UV lamp and why are quite interesting. The science is very important. And more reporting on the characteristic with pictures of the stone alongside a fluoro master would also be interesting.

But to pull away from that idea for a moment, I recall GIA teaching me that fluorescence was essentially an identifying characteristic-not a performance characteristic. And I believe the recent science bears out this view. And I really think this is where the rubber meets the road in this discussion.

Judging from the state of the science and the detection equipment available, it seems to me that we should be able to definitively determine under what conditions fluorescence can be activated and capable of producing any kind of color masking effects. I think the answer to this question is fundamental to the consumer.

Yes, overgrading of color, to whatever extent it is taking place, is obviously crucial to the consumer interest. But from what I gather from the comments in this thread, nobody is disputing the fact that overgrading of color can take place as a result of grading within a few inches of fluorescent tubes. Which is also why I cannot quite understand why people object to the recommendations made by Mr. Cowing in terms of improving the grading practice of fluoro stones.

But an equally important issue for consumers is understanding the practical implications of diamonds with fluorescent properties.

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

The following statements are copied and pasted from the 2010 study. This is what got my attention about how often the potential for activation of fluorescence in fluorescent diamonds is actually realized in real world viewing environments.

Measurements of UV content in natural and artificial lighting
The degree of any perceived colour improvement due to fluorescence is proportional to both the diamond’s fluorescent strength and the strength of the UV energy from the light source used in grading. A Dazor Model 5.7 (UVA + B) total UV instrument was employed to measure the amount of UV present in each lighting environment. This meter was calibrated to NIST standards, and measures the UV band from 280–400 nm over a range of 0 to 1999 µW/cm².

Typical measurements of UV in blue sky, northern daylight in Maryland, at 11:00 a.m. 7 December 2008, were 500–600 µW/cm². The UV rapidly increased as the detector was rotated south and the vicinity of the sun was approached. Near but not including direct sun, the reading quicklyexceeded the meter range of 1999 µW/cm².

Away from open daylight and indoors,the UV intensities dropped by factors of 100 to 1000, and in typical artificial light to less than 1 µW/cm2.

Are these statements in dispute? Please re-read the last sentence!

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

I'm no opponent of instrumental measurement either.
Byran, we also agree that this is a fundamental question for consumers.
That it is such an important question does not mean any easy or practical answers can be found.
For me, it's one of the coolest ( and most frustrating) aspects of diamonds. But part of that is the fact that there's just so much variation.

In terms of overall appearance, I'd say 10% of all SB/MB stones may have some negative impact- 80% neutral- and 10% special in the other way.
By "special" I mean a small percentage of high color MB/SB diamonds that actually look blue over a broad assortment of lighting. Back in the late '70's at Harry Winston, such stones were called "Premier" and sold at a nice premium over inert stones. I got to see these stones when I was in school there. We looked at them in darkened room with standard diamond lamps- and also in a room with normal office lighting. In fairness, the room with normal office lighting also had North facing windows. I'm sure we also looked on cloudy days.

I still love such stones.
So I've been observing this for decades.
There's no need to debate how much UV is or isn't present when the diamonds are giving us the answer.
Maybe the fact that the "Premier" stones would still look blue at night- if they were in a brightly lit room- and maybe that room had a factor of 10-100% less than standing at noon on a sunny day means that the devices measuring the UV are somehow missing the element that does cause this phenomenon.

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

I'm no opponent of instrumental measurement either.
Byran, we also agree that this is a fundamental question for consumers.
That it is such an important question does not mean any easy or practical answers can be found.
For me, it's one of the coolest ( and most frustrating) aspects of diamonds. But part of that is the fact that there's just so much variation.

In terms of overall appearance, I'd say 10% of all SB/MB stones may have some negative impact- 80% neutral- and 10% special in the other way.
By "special" I mean a small percentage of high color MB/SB diamonds that actually look blue over a broad assortment of lighting. Back in the late '70's at Harry Winston, such stones were called "Premier" and sold at a nice premium over inert stones. I got to see these stones when I was in school there. We looked at them in darkened room with standard diamond lamps- and also in a room with normal office lighting. In fairness, the room with normal office lighting also had North facing windows. I'm sure we also looked on cloudy days.

I still love such stones.
So I've been observing this for decades.
There's no need to debate how much UV is or isn't present when the diamonds are giving us the answer.
Maybe the fact that the "Premier" stones would still look blue at night- if they were in a brightly lit room- and maybe that room had a factor of 10-100% less than standing at noon on a sunny day means that the devices measuring the UV are somehow missing the element that does cause this phenomenon.

It's important to pay attention to what your eyes are telling you. But it's equally important to be aware of what modern science is discovering.

There was a time when people were sure that the earth was flat because that is what their eyes were telling them.

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

The following statements are copied and pasted from the 2010 study. This is what got my attention about how often the potential for activation of fluorescence in fluorescent diamonds is actually realized in real world viewing environments.

Measurements of UV content in natural and artificial lighting
The degree of any perceived colour improvement due to fluorescence is proportional to both the diamond’s fluorescent strength and the strength of the UV energy from the light source used in grading. A Dazor Model 5.7 (UVA + B) total UV instrument was employed to measure the amount of UV present in each lighting environment. This meter was calibrated to NIST standards, and measures the UV band from 280–400 nm over a range of 0 to 1999 µW/cm².

Typical measurements of UV in blue sky, northern daylight in Maryland, at 11:00 a.m. 7 December 2008, were 500–600 µW/cm². The UV rapidly increased as the detector was rotated south and the vicinity of the sun was approached. Near but not including direct sun, the reading quicklyexceeded the meter range of 1999 µW/cm².

Away from open daylight and indoors,the UV intensities dropped by factors of 100 to 1000, and in typical artificial light to less than 1 µW/cm2.

Are these statements in dispute? Please re-read the last sentence!

Yes Bryan because the instrument only covered the invisible excitation range.
Can I please get you to understand I am very focused on what Michael calls the Visible Violet (but extending to the blue on the spectrum).

And please do not ignore my statements that it is important to know what levels of light make it possible to notice face up color grade differences. I am very focused on consumers Bryan, that aught to be well known.

The fact that Michael wrote this: " Initial grading of the 25 diamonds in the data base indicated that at a brightness of 600 fc the grades recorded were slightly whiter than those recorded in light of 200 fc (i.e. within the range recommended above); in the absence of UV this was attributed to fluorescence stimulation by the visible violet."
That is my point.
Do you see that even with LED light that is almost totally devoid of Visible Violet - with enough light the grades improve. In my idealized experiment we would need several lighting types. I expect LED will show the least grade whitening and almost all other lightings, including daylight with and without open windows, will show that consumers are getting better grades for less money. Not the rip off that Michael is highlighting.
The question I am not scientist enough to identify is what foot per candle lighting is enough to make face up grade distinctions.
Please work with me guys.

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

I do not pretend to be an expert on lighting levels, but it seems from Michael's analysis that 200fc is the bare minimum needed to grade diamonds table down. I found the list below from a forum with no referrals.

Type
Lux
Foot Candles

Packing Work
150-300 (Lx)
15-30 (FC)

Production Work
300-750 (Lx)
30-75 (FC)

Inspection Work
750-1,500 (Lx)
75-150 (FC)

Detailed Assembly
1,500-3,000 (Lx)
150-300 (FC)
And from http://www.maximlighting.com/fpage_lighting_need.aspx
Room Foot Candles Needed
Living Room 10-20
Kitchen General30-40
Kitchen Stove 70-80
Kitchen Sink 70-80
Dining Room 30-40
Bed Room 10-20
Hall Way 5-10
Bathroom 70-80

So I expect our ability to grade table down in a normal living room might drop from single grades to say 2 or 3 grades - say you could only just pick D from F but not D from E.
Face up it might be difficult to tell a D from a G.
If that is the case, then it will only be in really bright light that the distinction between a strong blue "over graded H that is really an F according to MC" and a none fluoro stone sitting alongside it. And my contention is that in almost all such lightings there will be enough blue excitation to raise the H to at least a G if not an F or E.
In this regard I also wish to raise the issue that MC says there is no excitation into the blue past the violet 415 nm line. This is contradictory to what is shown in the G&G article Summer 2013. Bryan you accuse David of not reading MC's article - I would ask have you read this article?
http://www.gia.edu/gems-gemology/summer-2013-luo-fluorescence-optical-defects
This article states "the N3-related emission, which is not active with excitation energy above 435 nm" and further in:
"Even under pure 365 nm LWUV excitation, the fluorescence color will be a mixture of the fluorescence from different defect centers."
And especially for David: "For example, the intensity of N3 luminescence (measured at 439 nm) when excited by 400 nm excitation is approximately double that of the same emission measured at 360 nm excitation"
and
"Compared to 365 nm excitation, the fluorescence color with 405 nm excitation is almost twice as intense."

So I contend that unless we can conduct a proper experiment with eyes and diamonds, the science is not simple enough.
Smart consumers on Pricescope by and large love fluoro diamonds.
Most of the diamond pro's I know buy their spouses fluoro diamonds.
When I have my customers coming back saying i don't like this fluoro diamond, I will worry.
I do not see this happening. I understand it takes more skill and knowledge to sell Fluoro diamonds, and they neeed careful screening for the milky hazy dud's (which are possibly explained in the 2013 article too).

 

[Karl_K]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

There are really 3 related issues here:
The effect of florescence in the appearance of diamonds in the real world.
The biggest question is of lighting.
With modern lighting and led type lighting(among others) being the future and the push for uv free lighting.
Read the press releases from lighting companies, network control, variable colors, energy use and uv free are all talking points for the next generation of lighting.

Lab color grading:
While a study of 25 diamonds is a good start it is not possible with such a small sample to say it applies to all diamonds.
I have seen one with my own eyes that does not fit the data shown.
It looks like strong florescence in sunlight but is a lab rated none and tested under lab lighting showed none.
My opinion grading with as close to 0 uv would be the more consistent and accurate than using light sources with UV.

lab florescence grading:
The one thing everyone agrees with is that it is a mess.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Karl- GIA fluorescence grading might be a "mess", but in my opinion it's totally workable given the limitations which are imposed by the diamonds themselves.
There's literally an infinite combination of color/fl and face up results- so trying to assess a grade that will identify the subtle differences seems impossible.
In my mind this also addresses the issue of how much, or how little UV is hitting the diamond at color grading time. We'll have to pick a compromise ( which we already have) and no matter what the compromise it's not going to evenly affect every candidate stone.
Bottom line is that IMO all attempts to "comidify" diamonds will ultimately fail- instead requiring a one by one inspection.
The best help a consumer will get on this issue is a knowledgeable and honest seller. I don't see that changing.

Bryan- flying pigs = the earth is flat- so I guess I asked for that one

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

The following statements are copied and pasted from the 2010 study. This is what got my attention about how often the potential for activation of fluorescence in fluorescent diamonds is actually realized in real world viewing environments.

Measurements of UV content in natural and artificial lighting
The degree of any perceived colour improvement due to fluorescence is proportional to both the diamond’s fluorescent strength and the strength of the UV energy from the light source used in grading. A Dazor Model 5.7 (UVA + B) total UV instrument was employed to measure the amount of UV present in each lighting environment. This meter was calibrated to NIST standards, and measures the UV band from 280–400 nm over a range of 0 to 1999 µW/cm².

Typical measurements of UV in blue sky, northern daylight in Maryland, at 11:00 a.m. 7 December 2008, were 500–600 µW/cm². The UV rapidly increased as the detector was rotated south and the vicinity of the sun was approached. Near but not including direct sun, the reading quicklyexceeded the meter range of 1999 µW/cm².

Away from open daylight and indoors,the UV intensities dropped by factors of 100 to 1000, and in typical artificial light to less than 1 µW/cm2.

Are these statements in dispute? Please re-read the last sentence!

Yes Bryan because the instrument only covered the invisible excitation range.
Can I please get you to understand I am very focused on what Michael calls the Visible Violet (but extending to the blue on the spectrum).

And please do not ignore my statements that it is important to know what levels of light make it possible to notice face up color grade differences. I am very focused on consumers Bryan, that aught to be well known.

The fact that Michael wrote this: " Initial grading of the 25 diamonds in the data base indicated that at a brightness of 600 fc the grades recorded were slightly whiter than those recorded in light of 200 fc (i.e. within the range recommended above); in the absence of UV this was attributed to fluorescence stimulation by the visible violet."
That is my point.
Do you see that even with LED light that is almost totally devoid of Visible Violet - with enough light the grades improve. In my idealized experiment we would need several lighting types. I expect LED will show the least grade whitening and almost all other lightings, including daylight with and without open windows, will show that consumers are getting better grades for less money. Not the rip off that Michael is highlighting.
The question I am not scientist enough to identify is what foot per candle lighting is enough to make face up grade distinctions.
Please work with me guys.

Garry,
I think I am starting to understand your position. If I read you correctly, you are not taking exception to anything in the Cowing study regarding UV. You are basing your conclusions on the presence of wavelengths in the visible spectrum capable of exciting fluorescence. And so, you believe that as long as there is enough light to grade color by (within acceptable range of accuracy) there is enough VV present to activate blue fluoro and cause a whitening effect. Therefore, if the lab grade is rendered in a lighting environment where VV is present, that is as it should be since consumers will also be observing the diamond in visible light where VV is also present.

Is that a fair assessment of your argument?

Re-reading the GIA 2013 study (quite a heavy slog for a non-scientist!) I do see the results consistent with the fact that fluoro can be excited by wavelengths in the visible spectrum, which Michaels 2010 study also revealed. However, the GIA study focusses solely on the outputs of devices used for detection and observation of fluorescence, not on what energies are available in normal viewing scenarios and whether they are capable of exciting color masking degrees of fluoro. As a lay person with regard to this science, my takeaway from the article is how varied the devices are in terms of their various outputs and the fluoro colors and strengths observed, which results in significant inconsistencies in gemological reporting on this property. It also breaks down the different types of color centers and how they react to different energies individually and in combination where multiple color centers are present in the same stone.

Here is where I don't follow your train of thought. You say, and this seems to be a central basis for your position, "And my contention is that in almost all such lightings there will be enough blue excitation to raise the H to at least a G if not an F or E."

On what do you base that contention? As we saw in the Cowing study, the mere presence of UV and/or VV in the light source is not the operative factor. It must be of sufficient intensity to stimulate a color masking degree of fluorescence. And the Cowing study did measure intensity as a function of distance from the light source and found that after a short distance the intensity dropped off to essentially zero in artificial light.

From the cowing study "In all other areas illuminated by artificial fluorescent and incandescent ceiling illumination the readings at typical 3–4 ft viewing distances from ceiling lights were an essentially UV-free, 0–1 µW/cm2."

If this is correct, then logically, even if other wavelengths are present which can potentially stimulate fluorescence, they too would drop off so dramatically in intensity that they would not be able to activate fluoro color masking in normal everyday viewing environments.

So again, while the study of the causes of fluorescence is interesting, and the survey of the outputs of the various devices commonly used to observe and report fluoro show a level of variability that calls for a better and more consistent way to grade it, the real issue for consumers is what affect on appearance of their diamond is or is not happening in real world viewing environments.

It sure seems to me that with these various sophisticated instruments as specified in both articles, we should be able to answer that question with a pretty high level of confidence.

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

There are really 3 related issues here:
The effect of florescence in the appearance of diamonds in the real world.
The biggest question is of lighting.
With modern lighting and led type lighting(among others) being the future and the push for uv free lighting.
Read the press releases from lighting companies, network control, variable colors, energy use and uv free are all talking points for the next generation of lighting.

Lab color grading:
While a study of 25 diamonds is a good start it is not possible with such a small sample to say it applies to all diamonds.
I have seen one with my own eyes that does not fit the data shown.
It looks like strong florescence in sunlight but is a lab rated none and tested under lab lighting showed none.
My opinion grading with as close to 0 uv would be the more consistent and accurate than using light sources with UV.

lab florescence grading:
The one thing everyone agrees with is that it is a mess.

Karl have you heard about the revival of the tungsten light globe?
Promises to be 1/2 the running cost of LED's by 'recycling' the infra red heat to improve efficiency and retain the same wonderful light.

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

The following statements are copied and pasted from the 2010 study. This is what got my attention about how often the potential for activation of fluorescence in fluorescent diamonds is actually realized in real world viewing environments.

Measurements of UV content in natural and artificial lighting
The degree of any perceived colour improvement due to fluorescence is proportional to both the diamond’s fluorescent strength and the strength of the UV energy from the light source used in grading. A Dazor Model 5.7 (UVA + B) total UV instrument was employed to measure the amount of UV present in each lighting environment. This meter was calibrated to NIST standards, and measures the UV band from 280–400 nm over a range of 0 to 1999 µW/cm².

Typical measurements of UV in blue sky, northern daylight in Maryland, at 11:00 a.m. 7 December 2008, were 500–600 µW/cm². The UV rapidly increased as the detector was rotated south and the vicinity of the sun was approached. Near but not including direct sun, the reading quicklyexceeded the meter range of 1999 µW/cm².

Away from open daylight and indoors,the UV intensities dropped by factors of 100 to 1000, and in typical artificial light to less than 1 µW/cm2.

Are these statements in dispute? Please re-read the last sentence!

Yes Bryan because the instrument only covered the invisible excitation range.
Can I please get you to understand I am very focused on what Michael calls the Visible Violet (but extending to the blue on the spectrum).

And please do not ignore my statements that it is important to know what levels of light make it possible to notice face up color grade differences. I am very focused on consumers Bryan, that aught to be well known.

The fact that Michael wrote this: " Initial grading of the 25 diamonds in the data base indicated that at a brightness of 600 fc the grades recorded were slightly whiter than those recorded in light of 200 fc (i.e. within the range recommended above); in the absence of UV this was attributed to fluorescence stimulation by the visible violet."
That is my point.
Do you see that even with LED light that is almost totally devoid of Visible Violet - with enough light the grades improve. In my idealized experiment we would need several lighting types. I expect LED will show the least grade whitening and almost all other lightings, including daylight with and without open windows, will show that consumers are getting better grades for less money. Not the rip off that Michael is highlighting.
The question I am not scientist enough to identify is what foot per candle lighting is enough to make face up grade distinctions.
Please work with me guys.

Garry,
I think I am starting to understand your position. If I read you correctly, you are not taking exception to anything in the Cowing study regarding UV. You are basing your conclusions on the presence of wavelengths in the visible spectrum capable of exciting fluorescence. And so, you believe that as long as there is enough light to grade color by (within acceptable range of accuracy) there is enough VV present to activate blue fluoro and cause a whitening effect. Therefore, if the lab grade is rendered in a lighting environment where VV is present, that is as it should be since consumers will also be observing the diamond in visible light where VV is also present.

Is that a fair assessment of your argument?
Yes Bryan, thanks, you nailed it

Re-reading the GIA 2013 study (quite a heavy slog for a non-scientist!) I do see the results consistent with the fact that fluoro can be excited by wavelengths in the visible spectrum, which Michaels 2010 study also revealed. However, the GIA study focusses solely on the outputs of devices used for detection and observation of fluorescence, not on what energies are available in normal viewing scenarios and whether they are capable of exciting color masking degrees of fluoro. As a lay person with regard to this science, my takeaway from the article is how varied the devices are in terms of their various outputs and the fluoro colors and strengths observed, which results in significant inconsistencies in gemological reporting on this property. It also breaks down the different types of color centers and how they react to different energies individually and in combination where multiple color centers are present in the same stone.

Here is where I don't follow your train of thought. You say, and this seems to be a central basis for your position, "And my contention is that in almost all such lightings there will be enough blue excitation to raise the H to at least a G if not an F or E."

On what do you base that contention? As we saw in the Cowing study, the mere presence of UV and/or VV in the light source is not the operative factor. It must be of sufficient intensity to stimulate a color masking degree of fluorescence. And the Cowing study did measure intensity as a function of distance from the light source and found that after a short distance the intensity dropped off to essentially zero in artificial light.
Exactly - the intensity of all light drops away on a squared function of distance. And so too does our ability to percieve these very subtle color differences.
From the cowing study "In all other areas illuminated by artificial fluorescent and incandescent ceiling illumination the readings at typical 3–4 ft viewing distances from ceiling lights were an essentially UV-free, 0–1 µW/cm2."
Michael used an instrument that measured UV light, not VV light - the VV light comes through windows, Lexan, and is all around us. If it were not present you would see a woman wearing a violet dress as grey. If I take a photo of an ASET in cloudy daylight coming through a window with my 415 nm filter, the colours are all shades of purplish grey.
If this is correct, then logically, even if other wavelengths are present which can potentially stimulate fluorescence, they too would drop off so dramatically in intensity that they would not be able to activate fluoro color masking in normal everyday viewing environments. Again, my contention is that if there is enough light to make small grade separations, then there is adequate light to have grade improving excitation.

So again, while the study of the causes of fluorescence is interesting, and the survey of the outputs of the various devices commonly used to observe and report fluoro show a level of variability that calls for a better and more consistent way to grade it, the real issue for consumers is what affect on appearance of their diamond is or is not happening in real world viewing environments.

It sure seems to me that with these various sophisticated instruments as specified in both articles, we should be able to answer that question with a pretty high level of confidence.

I am open to any suggestion that help solve this conundrum Bryan.
But there is a common fact that the vast number of experienced non brain washed sales people dealing with the public will tell you that medium and strong blue fluoro diamonds are liked and even preferred by many consumers. You have seen the polls taken here on Pricescope. I am not making that up, am I?
But I would love to have some scientific or survey based evidence to prove it.

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

This graphic with the VV and blue added might help

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Garry,
Your argument seems to rest on a notion that the wavelengths in visible light capable of activating fluorescence somehow behave differently than those in the UV range. That is, you seem to be saying that the UV in an overhead fluorescent light is not strong enough to stimulate grade whitening fluorescence, but somehow the VV in the light is. On what are you basing that? I have not seen anything in either of the studies mentioned here that supports that. In fact, the 3D profile done by Hainshwang in Cowing study shows the fluoro strength caused by the VV wavelengths to be weaker than those in the UV.

If they drop off in intensity proportionately, and UV is no longer capable of activating fluoro, then VV are similarly incapable. If no fluoro activation is taking place , then fluoro-driven grade whitening cannot be either. And any surveys or expressed preferences that suggest otherwise would have to be the result of something other than fluorescence.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

There's absolutely no one who ( other than you) who is disputing the grade whitening phenomena exists.
Besides everything Garry just mentioned, I promise, I did not make up the fact Harry Winston used to get a premium for diamonds that had this characteristic.
They were called "Premier"- I can't find a way to look it up, but it's a fact.

To me - a person who has great respect for science, and an inquiring mind- but not to the extent I want to take the effort necessary to understand the nifty graphs that are being displayed.... it's such a moot point as to why.
But I respect those like Garry- and Michael- who take time to research these aspects. Clearly there's a lot to learn- but it all begins with physical observation. As opposed to trying to measure light with tools. Using the tools to verify what we see makes sense.
Trying to interpret them to dispute a physical reality seems off target.