Article Over Grading of Blue Fluorescent Diamonds Revisited

[pfunk]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Wow, these were 8 pages of dense reading to navigate through, but I enjoyed the exchanges despite the fact it seems like two sides that are both convinced they are "right" and don't want to budge. I'm taking some time to review some of the literature and hope to come back with some "outsider" questions that might stimulate constructive exchanges. A few more basic questions first that I hope will be answered without any references to literature:

For Michael... have you ever viewed a blue fluorescent diamond that showed color improvement that you think it shouldn't have shown? Meaning it was viewed at a distance that SHOULD have ensured that any lighting, whether UV or VV, would have had insufficient energy to stimulate whitening? In other words, have you ever had a diamond that stumped you during your research (or even when not actively researching for that matter)? One that broke the rules?

How many diamonds have you formally studied under your controlled lighting environments? (I am sure I will get this when I review all of the literature but I'm curious as to the number when including unpublished work of yours)

Michael and Bryan can field these... what are your responses to the professionals who claim to regularly see fluorescent stones whiten in environments that you have determined CAN'T be conducive to whitening due to fluorescence? Have you hypothesized as to what it might be that causes these stones to whiten even though you believe the lighting environments shouldn't allow such whitening? Or do you think they are off their rockers and they aren't really seeing whitening like they think think they are?

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Really great Q's pfunk! Thank you for asking them and pointing out both sides seemingly un-movable positions.

I have also enjoyed this discussion a lot because although we are disputing each other, we are at least discussing and exchanging ideas. Wish there was more of that going around.

Pfunk- in your own personal experience, have you ever been able to distinguish differences in colorless diamonds? Like comparing a D to an H for example.....

 

[pfunk]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Really great Q's pfunk! Thank you for asking them and pointing out both sides seemingly un-movable positions.

I have also enjoyed this discussion a lot because although we are disputing each other, we are at least discussing and exchanging ideas. Wish there was more of that going around.

Pfunk- in your own personal experience, have you ever been able to distinguish differences in colorless diamonds? Like comparing a D to an H for example.....

David, I am thoroughly unexperienced when it comes to any sort of grading diamonds (color included) and will be the first to admit it. My experience encompasses only several hours of b&m diamond viewing leading up to the purchase of my wife's engagement ring. In that very limited timeframe and in jewelry store lighting, I would say that I could fairly consistently see the difference of 2 color grades when viewed table down on a white background. This is in the g-h-i-j range. In the limited time that I viewed higher color stones, I found it much more difficult to discern those differences and my guesses as to the colors were less accurate. In the face up position, it became harder still.

I would LOVE to have the time and resources to try to train my eye, but its not like I can go sit down in a jewelry store and tell them I'm there to "learn".

 

[pfunk]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Michael, as I read your paper I have a couple more questions for you. I am personally more experienced with reading medical journals (more specifically pharmaceutical research) and am accustomed to finding the "limitations" section at the end. I am curious as to whether you formulated a list of limitations and what that list may look like?

As a reader, the first question I am asking myself is what are your credentials and training as a diamond grader?
What sort of master set of stones did you use for your grading of these 25 stones?
Was the selection of diamonds to be used done at random and why only 25 stones?
Were the specified light sources the ONLY source of light in the room at the time of grading?

I hope you don't take these questions as an indication of me trying to poke holes in your study. They are very real questions I would like to know in order to evaluate the study. I happen to come into this discussion feeling like a UV filter should be used for diamond grading and don't see why the use of a filter would be detrimental to the consumer. If UV light is causing a chameleon effect on stones that is dependent upon the lighting it should be eliminated as a variable, especially considering that we don't know why certain fluorescing stones behave one way and others seem to behave another way.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Cool Pfunk!
Although you'd need to use many diamonds, in person, to see if you're qualified to grade color, part of the value of a discussion like this is educating consumers on more specifics about grading.
Your experience shows us something important.
You could see the difference more easily in low colors- here's why:
The diamond color grade scale is not a consistent, linear scale. Every grade has a range, and they're not equal
The potential difference between a "high D" and a "low E" is a fraction of the distance between a high I and a low J.
I like to use a ruler analogy.
If there's an inch difference between High D and Low E, there's a foot's difference between the High I and Low J.
This is directly related to our discussion.
I am NOT a scientist- but as a diamond grader, I understand that the variation possible within J is so very complex, that trying to pin down a more accurate way to calibrate these different colors is impossible due to the variation.
Fluoro is so similar- but even less consistent.

 

[sharonp]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Michael, as I read your paper I have a couple more questions for you. I am personally more experienced with reading medical journals (more specifically pharmaceutical research) and am accustomed to finding the "limitations" section at the end. I am curious as to whether you formulated a list of limitations and what that list may look like?

As a reader, the first question I am asking myself is what are your credentials and training as a diamond grader?
What sort of master set of stones did you use for your grading of these 25 stones?
Was the selection of diamonds to be used done at random and why only 25 stones?
Were the specified light sources the ONLY source of light in the room at the time of grading?

I hope you don't take these questions as an indication of me trying to poke holes in your study. They are very real questions I would like to know in order to evaluate the study. I happen to come into this discussion feeling like a UV filter should be used for diamond grading and don't see why the use of a filter would be detrimental to the consumer. If UV light is causing a chameleon effect on stones that is dependent upon the lighting it should be eliminated as a variable, especially considering that we don't know why certain fluorescing stones behave one way and others seem to behave another way.

Welcome Pfunk great to have a second consumer participating here. I think you would benefit from reading the entire thread (or at least back to page 5 or 6), many of your questions have already been asked by me and answered by Michael Cowing (I bolded them).

 

[sharonp]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Sharonp- thank you so much for keeping the discussion lively, and relevant.
A few points about your last posts:
The study was of 25 diamonds. That is far too small a sample to have any meaning whatsoever in terms of "trends"
I don't need to "prove" Michael wrong, GIA is the final arbiter in this business. He would need to prove GIA wrong, and he has not.
If Michael wants his claims to have any validity, his grades would need to be peer reviewed- just like GIA does. Michael's grades are unproven, and therefore unreliable.
I get countless dealers and cutters "promising" GIA grades on uncertifed diamonds.
One of the first lessons a buyer learns is- do not trust anything BUT GIA grades.

Well if your only acceptable standard is getting GIA-GTL to regrade these specific stones or an even larger dataset, and modifying their grading box to do so you have a wildly unrealistic standard. GIA-GTL does not have an open door policy when it comes to outside research or questioning their grading practices. They also are very slow to change anything as they run a business first priority and education is a distant second.

"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."

With that attitude the only valid research in diamond grading is done by GIA in G&G and we should ignore all other published literature. Thats a pretty disruptive opinion to hold on to at this point.

If you won't even accept AGSL grading then really you have never wanted to educate consumers in this thread and have only been posting to disparage the work.

 

[pfunk]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

I have read the entire thread, but it was A LOT of material all at once. My questions arose after reading the published study, and I didn't see the answers to those questions. I aologize if I missed them, but I don't have the time to reread through the full thread to try to find those answers amongst all the text. If you or Michael (or anyone else who knows) could answer them it would be much appreciated. I remember posts about the lighting environments but dont recall it being mentioned whether there were other sources of light inside the grading environment that werent mentioned. Or was all grading done in a room with no windows and only the single light source (ie DiamondDock, microscope, etc)

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Wow, these were 8 pages of dense reading to navigate through, but I enjoyed the exchanges despite the fact it seems like two sides that are both convinced they are "right" and don't want to budge. I'm taking some time to review some of the literature and hope to come back with some "outsider" questions that might stimulate constructive exchanges. A few more basic questions first that I hope will be answered without any references to literature:

For Michael... have you ever viewed a blue fluorescent diamond that showed color improvement that you think it shouldn't have shown? Meaning it was viewed at a distance that SHOULD have ensured that any lighting, whether UV or VV, would have had insufficient energy to stimulate whitening? In other words, have you ever had a diamond that stumped you during your research (or even when not actively researching for that matter)? One that broke the rules?

How many diamonds have you formally studied under your controlled lighting environments? (I am sure I will get this when I review all of the literature but I'm curious as to the number when including unpublished work of yours)

Michael and Bryan can field these... what are your responses to the professionals who claim to regularly see fluorescent stones whiten in environments that you have determined CAN'T be conducive to whitening due to fluorescence? Have you hypothesized as to what it might be that causes these stones to whiten even though you believe the lighting environments shouldn't allow such whitening? Or do you think they are off their rockers and they aren't really seeing whitening like they think think they are?

P,
Good to see you participating here. I have always found you to be an open minded examiner of the issues, with insightful questions and comments. Moreover, you always seem to bring a sense of fairness and respect to discussions that helps make them more professional and constructive.

Regarding my take on your questions (bolded by me) above:
With regard to the most common type of blue fluorescent diamonds (Type 1A with N3 defects), the mechanism of the fluorescent effect is quite well understood, as is the yellow-cancelling, grade-whitening effect discussed in the Cowing study. The historical perspective Cowing gives is instructive in the sense that the concept being discussed is not new, nor are the potential implications for color grading accuracy. The GIA study that Garry referenced also discusses fluorescence caused by other defects that are less well understood, but comprise only a small fraction of the diamonds in the normal range. (That study also details the light output by different instruments used in laboratory and trade practices and provides great understanding of the variability in the observation and reporting on fluorescence.)

Given what we know about the mechanism and the components in different lighting scenarios that are capable of activating fluorescence, particularly to a level that would result in grade whitening, it seems very unlikely that most of the reports of appearance improvement in normal indoor lighting due to fluorescence are accurate.

Since I have been in the diamond business a long time, I am very familiar with the almost universal and unquestioned belief that a blue fluorescent diamond will generally look whiter than it's lab grade would indicate. My educated guess at this point is that this is largely an industry myth driven by several factors including the widespread trade practice of regularly examining diamonds very close to fluorescent desk lamps and/or in sunlight. Suggestibility is another reason that this notion may be perpetuated, along with the fact that it is a "benefit" that merchants find helpful in the sales process.

The case for VV light as a source of the whitening being reported in indoor lighting is intriguing. However, from what I have seen presented so far that case is difficult to make considering the light intensities required, which far exceed normal indoor lighting levels.

 

[pfunk]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Sharonp- thank you so much for keeping the discussion lively, and relevant.
A few points about your last posts:
The study was of 25 diamonds. That is far too small a sample to have any meaning whatsoever in terms of "trends"
I don't need to "prove" Michael wrong, GIA is the final arbiter in this business. He would need to prove GIA wrong, and he has not.
If Michael wants his claims to have any validity, his grades would need to be peer reviewed- just like GIA does. Michael's grades are unproven, and therefore unreliable.
I get countless dealers and cutters "promising" GIA grades on uncertifed diamonds.
One of the first lessons a buyer learns is- do not trust anything BUT GIA grades.

Well if your only acceptable standard is getting GIA-GTL to regrade these specific stones or an even larger dataset, and modifying their grading box to do so you have a wildly unrealistic standard. GIA-GTL does not have an open door policy when it comes to outside research or questioning their grading practices. They also are very slow to change anything as they run a business first priority and education is a distant second.

"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."

With that attitude the only valid research in diamond grading is done by GIA in G&G and we should ignore all other published literature. Thats a pretty disruptive opinion to hold on to at this point.

If you won't even accept AGSL grading then really you have never wanted to educate consumers in this thread and have only been posting to disparage the work.

I think what David is saying, at least in part, is that Michael is the only person assigning grades to the stones. Those values represent a singular opinion, and when a stone is graded at GIA, isn't it assessed by multiple graders before being given a final grade?

I too think 25 stones is a small sample when you consider that's only 5 stones (approximately, after considering inconsistencies between labs) for each fluorescence grade. When we look at medical type research we like to look for "statistical significance" and also assess the "power" of the study. Increasing sample sizes make the study more powerful and allow you to recognize differences that you can deem statistically significant. Now, I completely understand there is nowhere near the funding or resources to acheive this in a study such as Michael's, and I am impressed with what he put together. It is very interesting and has prompted me to ask more questions. I think the data he has gathered is enough to make us seriously question that there is very possibly a problem happening with overgrading color in fluoro stones, but I certainly think there remains work to be done to prove that it's a widespread issue that warrants major change (i.e. Policy changes at the major labs). His findings are in direct contradiction to what many longtime professionals of the trade are saying they see regularly (fluoro stones looking whiter than their true body color). He is stating in normal indoor lighting people SHOULD NOT (because of the science of lighting) see whitening of fluoro stones. He therefore feels the only place the perceived color should show whitening is outdoors in the sun, or indoors very close to a uv source (or even closer to a vv source). But then you have countless people saying that just doesn't add up, because they DO see whitening in those environments. So what is the variable that we arent picking up that is causing those stones to look whiter?

Essentially what we have here are professionals (David and Garry) growing angry because Michael's research is telling them not to believe what they are seeing. That it just can't be happening. Sure that is one possibility, but there is the chance that it IS happening but whatever is causing it still hasn't been nailed down and we need to keep looking. And if there is something about fluoro stones that causes them to look whiter without having to be in intense UV/VV, then maybe the current grading practices and instruments are fine how they are.

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Sharonp- thank you so much for keeping the discussion lively, and relevant.
A few points about your last posts:
The study was of 25 diamonds. That is far too small a sample to have any meaning whatsoever in terms of "trends"
I don't need to "prove" Michael wrong, GIA is the final arbiter in this business. He would need to prove GIA wrong, and he has not.
If Michael wants his claims to have any validity, his grades would need to be peer reviewed- just like GIA does. Michael's grades are unproven, and therefore unreliable.
I get countless dealers and cutters "promising" GIA grades on uncertifed diamonds.
One of the first lessons a buyer learns is- do not trust anything BUT GIA grades.

Well if your only acceptable standard is getting GIA-GTL to regrade these specific stones or an even larger dataset, and modifying their grading box to do so you have a wildly unrealistic standard. GIA-GTL does not have an open door policy when it comes to outside research or questioning their grading practices. They also are very slow to change anything as they run a business first priority and education is a distant second.

"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."

With that attitude the only valid research in diamond grading is done by GIA in G&G and we should ignore all other published literature. Thats a pretty disruptive opinion to hold on to at this point.

If you won't even accept AGSL grading then really you have never wanted to educate consumers in this thread and have only been posting to disparage the work.

I think what David is saying, at least in part, is that Michael is the only person assigning grades to the stones. Those values represent a singular opinion, and when a stone is graded at GIA, isn't it assessed by multiple graders before being given a final grade?

I too think 25 stones is a small sample when you consider that's only 5 stones (approximately, after considering inconsistencies between labs) for each fluorescence grade. When we look at medical type research we like to look for "statistical significance" and also assess the "power" of the study. Increasing sample sizes make the study more powerful and allow you to recognize differences that you can deem statistically significant. Now, I completely understand there is nowhere near the funding or resources to acheive this in a study such as Michael's, and I am impressed with what he put together. It is very interesting and has prompted me to ask more questions. I think the data he has gathered is enough to make us seriously question that there is very possibly a problem happening with overgrading color in fluoro stones, but I certainly think there remains work to be done to prove that it's a widespread issue that warrants major change (i.e. Policy changes at the major labs). His findings are in direct contradiction to what many longtime professionals of the trade are saying they see regularly (fluoro stones looking whiter than their true body color). He is stating in normal indoor lighting people SHOULD NOT (because of the science of lighting) see whitening of fluoro stones. He therefore feels the only place the perceived color should show whitening is outdoors in the sun, or indoors very close to a uv source (or even closer to a vv source). But then you have countless people saying that just doesn't add up, because they DO see whitening in those environments. So what is the variable that we arent picking up that is causing those stones to look whiter?

Essentially what we have here are professionals (David and Garry) growing angry because Michael's research is telling them not to believe what they are seeing. That it just can't be happening. Sure that is one possibility, but there is the chance that it IS happening but whatever is causing it still hasn't been nailed down and we need to keep looking. And if there is something about fluoro stones that causes them to look whiter without having to be in intense UV/VV, then maybe the current grading practices and instruments are fine how they are.

I don't see it that way (my bold). Michael's study doesn't directly dispute any observations of whitening that may be happening in some lighting environments. His position is that the labs should report un-enhanced color. Any whitening that may take place due to fluoro or VV would then be a true benefit and would tend to reverse the blanket discounting of a large portion of fluoro stones in the market.

 

[sharonp]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Essentially what we have here are professionals (David and Garry) growing angry because Michael's research is telling them not to believe what they are seeing. That it just can't be happening. Sure that is one possibility, but there is the chance that it IS happening but whatever is causing it still hasn't been nailed down and we need to keep looking. And if there is something about fluoro stones that causes them to look whiter without having to be in intense UV/VV, then maybe the current grading practices and instruments are fine how they are.

I don't see it that way (my bold). Michael's study doesn't directly dispute any observations of whitening that may be happening in some lighting environments. His position is that the labs should report un-enhanced color. Any whitening that may take place due to fluoro or VV would then be a true benefit and would tend to reverse the blanket discounting of a large portion of fluoro stones in the market.

Exactly, his paper confirms whitening in the GRADING Environment, and his solutions are about changing GRADING lighting, it isn't about subjective comments about beauty or personal preference or about changing the public's perception of Fluorescence or about making vague estimates of how uncontrolled consumer lighting does or does not cause contain the UV or VV required to cause grade whitening. It certainly doesn't contain any grading in the results that was done with faceup diamonds which is how most consumers view them.

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Sharonp- thank you so much for keeping the discussion lively, and relevant.
A few points about your last posts:
The study was of 25 diamonds. That is far too small a sample to have any meaning whatsoever in terms of "trends"
I don't need to "prove" Michael wrong, GIA is the final arbiter in this business. He would need to prove GIA wrong, and he has not.
If Michael wants his claims to have any validity, his grades would need to be peer reviewed- just like GIA does. Michael's grades are unproven, and therefore unreliable.
I get countless dealers and cutters "promising" GIA grades on uncertifed diamonds.
One of the first lessons a buyer learns is- do not trust anything BUT GIA grades.

Well if your only acceptable standard is getting GIA-GTL to regrade these specific stones or an even larger dataset, and modifying their grading box to do so you have a wildly unrealistic standard. GIA-GTL does not have an open door policy when it comes to outside research or questioning their grading practices. They also are very slow to change anything as they run a business first priority and education is a distant second.

"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."

With that attitude the only valid research in diamond grading is done by GIA in G&G and we should ignore all other published literature. Thats a pretty disruptive opinion to hold on to at this point.

If you won't even accept AGSL grading then really you have never wanted to educate consumers in this thread and have only been posting to disparage the work.

I think what David is saying, at least in part, is that Michael is the only person assigning grades to the stones. Those values represent a singular opinion, and when a stone is graded at GIA, isn't it assessed by multiple graders before being given a final grade?

I too think 25 stones is a small sample when you consider that's only 5 stones (approximately, after considering inconsistencies between labs) for each fluorescence grade. When we look at medical type research we like to look for "statistical significance" and also assess the "power" of the study. Increasing sample sizes make the study more powerful and allow you to recognize differences that you can deem statistically significant. Now, I completely understand there is nowhere near the funding or resources to acheive this in a study such as Michael's, and I am impressed with what he put together. It is very interesting and has prompted me to ask more questions. I think the data he has gathered is enough to make us seriously question that there is very possibly a problem happening with overgrading color in fluoro stones, but I certainly think there remains work to be done to prove that it's a widespread issue that warrants major change (i.e. Policy changes at the major labs). His findings are in direct contradiction to what many longtime professionals of the trade are saying they see regularly (fluoro stones looking whiter than their true body color). He is stating in normal indoor lighting people SHOULD NOT (because of the science of lighting) see whitening of fluoro stones. He therefore feels the only place the perceived color should show whitening is outdoors in the sun, or indoors very close to a uv source (or even closer to a vv source). But then you have countless people saying that just doesn't add up, because they DO see whitening in those environments. So what is the variable that we arent picking up that is causing those stones to look whiter?

Essentially what we have here are professionals (David and Garry) growing angry because Michael's research is telling them not to believe what they are seeing. That it just can't be happening. Sure that is one possibility, but there is the chance that it IS happening but whatever is causing it still hasn't been nailed down and we need to keep looking. And if there is something about fluoro stones that causes them to look whiter without having to be in intense UV/VV, then maybe the current grading practices and instruments are fine how they are.

Just to be clear, the diamonds in the study were graded by GIA and AGSL, in addition to the author. And the basic findings of the study were consistent with the results of an earlier study by Tashey.

And it may be interesting to note that the GIA study that Garry referenced, which nobody seems to be questioning the validity of, just happens to have used the same sample size - 25 diamonds. I understand that the goals of the studies were completely different, but the point is that a study cannot be legitimately dismissed simply because a larger sample size might have been more statistically significant.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Yes Sharon, we're speaking, in part, about diamond grading.
I'm using actual diamonds during this discussion.
Rarely a day goes by that we are not picking up or dropping off a diamond at GIA for grading.
Pretty much all of what I'm saying is corroborated on my site, where I frequently publish my estimated grades, then GIA results.
BTW_ my experience is that GIA's color grading is remarkably consistent. Lately we have been getting new reports for some older stones that were originally graded 8 years ago or more. I don't give the the old report- just submit the diamond so that I get a true "new" grade.
Color changes - even from 15 year old reports- are remarkably rare.
IN cases where I have disagreed with GIA color grades and gone for the re-check- changes are also extremely rare, but we have succeeded a few times.

Bryan has been asked repeatedly by Garry to perform some simple tests using actual diamonds.
Instead Bryan is relying on Micheal's research to "prove" that the whitening element in certain diamonds ( by no means all) can't be activated by many different lighting sources.
This logic will mean GIA is doing something terribly underhanded and overgrading diamonds.

SO, yes, we're discussing diamond grading.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Just to be clear, the diamonds in the study were graded by GIA and AGSL, in addition to the author. And the basic findings of the study were consistent with the results of an earlier study by Tashey.

And it may be interesting to note that the GIA study that Garry referenced, which nobody seems to be questioning the validity of, just happens to have used the same sample size - 25 diamonds. I understand that the goals of the studies were completely different, but the point is that a study cannot be legitimately dismissed simply because a larger sample size might have been more statistically significant.

Bryan-I count only 15 stones graded by GIA in Michael's study.
Furthermore, in terms of credibility we simply can't depend on a study published by Michael ( or any such author) on the same level as one done by GIA.
You've never ever touched my criticism of Michael's grade being taken for gospel, or the problems that creates in this study Bryan. And neither has Michael touched on this aspect.

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Yes Sharon, we're speaking, in part, about diamond grading.
I'm using actual diamonds during this discussion.
Rarely a day goes by that we are not picking up or dropping off a diamond at GIA for grading.
Pretty much all of what I'm saying is corroborated on my site, where I frequently publish my estimated grades, then GIA results.
BTW_ my experience is that GIA's color grading is remarkably consistent. Lately we have been getting new reports for some older stones that were originally graded 8 years ago or more. I don't give the the old report- just submit the diamond so that I get a true "new" grade.
Color changes - even from 15 year old reports- are remarkably rare.
IN cases where I have disagreed with GIA color grades and gone for the re-check- changes are also extremely rare, but we have succeeded a few times.

Bryan has been asked repeatedly by Garry to perform some simple tests using actual diamonds.
Instead Bryan is relying on Micheal's research to "prove" that the whitening element in certain diamonds ( by no means all) can't be activated by many different lighting sources.
This logic will mean GIA is doing something terribly underhanded and overgrading diamonds.

SO, yes, we're discussing diamond grading.

Send me the diamonds you want me to perform simple tests on and I will be happy to do them. Otherwise please refrain from insinuating that I am somehow trying to hide something.

The fact that an author comes here to discuss/explain/defend his work does not give Garry or you or anyone else the right to demand that they conduct some other study.

Frankly, the kind of attitude that you have demonstrated throughout this discussion would make any other serious gemologist very reluctant to come here to share his work. And that is a loss for the whole pricescope community.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Hi Bryan,
I'm generally a pretty plain speaker, so please no need to insert words into my mouth.
I have never insinuated you're trying to hide something, or doing anything underhanded whatsoever.
The suggestion to use live diamonds as opposed to relying on a study seems quite practical.

I'm also not demanding anybody do anything. Don't conduct any live testing- your choice.
That is completely a separate issue with questioning the findings of this ( or any) study.

If a gemologist is afraid of thorough peer review, that they should not participate here. But if their study is quoted here, it's going to be looked at.
This is to the benefit of consumers.

 

[pfunk]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Essentially what we have here are professionals (David and Garry) growing angry because Michael's research is telling them not to believe what they are seeing. That it just can't be happening. Sure that is one possibility, but there is the chance that it IS happening but whatever is causing it still hasn't been nailed down and we need to keep looking. And if there is something about fluoro stones that causes them to look whiter without having to be in intense UV/VV, then maybe the current grading practices and instruments are fine how they are.

I don't see it that way (my bold). Michael's study doesn't directly dispute any observations of whitening that may be happening in some lighting environments. His position is that the labs should report un-enhanced color. Any whitening that may take place due to fluoro or VV would then be a true benefit and would tend to reverse the blanket discounting of a large portion of fluoro stones in the market.

Exactly, his paper confirms whitening in the GRADING Environment, and his solutions are about changing GRADING lighting, it isn't about subjective comments about beauty or personal preference or about changing the public's perception of Fluorescence or about making vague estimates of how uncontrolled consumer lighting does or does not cause contain the UV or VV required to cause grade whitening. It certainly doesn't contain any grading in the results that was done with faceup diamonds which is how most consumers view them.

The paper confirms whitening, by a single grader, on a set of stones that were selected in a way we know nothing about. Who selected these stones and was it done at random? Had these stones been examined by Michael prior to the study or did he or someone else choose them prior to the study without any prior examination?

Certainly I agree that the labs should be reporting unenhanced color, and if there is a phenomenon taking place that we need to account for then absolutely change needs to be considered. But if typical lighting environments (not just UV rich sunlight and bright light containing VV) are causing stones to whiten, isn't their predominant "perceived" color the higher color anyway?

Let me ask this... you've all been around pricescope for a considerable amount of time. Can you recall or link any examples of folks complaining about their fluorescent stones turning yellow and leaving them disappointed? Cases where they complain that they or an appraiser have noticed their stones look more yellow than they should? I sure think that if the labs were getting these wrong by 2-4 grades there would be a considerable amount of unhappy customers who feel let down by the laboratories and voice their opinions online.

Having said all this, and like I said before, I as a consumer would be in favor of returning to the practice of grading in UV free environments. It just makes sense to grade all stones in UV free environments when there are plenty of data to show that these stones whiten when exposed to strong UV.

The debate seems to be whether more typical environments can also illicit the whitening effect. Many people seem to think the answer is yes, and that the stones don't need to be in sunlight or within 7 inches of the UV containing light to whiten. But when it comes to laboratory grading, I say who cares at what point or in which lighting the stones will whiten as long as I know they were all graded with whitening due to fluoro taken out of the equation. The reason for this is because the whitening due to flouro seems to be an unpredictable event, so all stones should be graded in UV free environments. The stones that show a tendency to whiten can then be sold at a premium and consumers can seek these out if they wish to do so. The seller will know they have something special and price it accordingly. Consumers can choose to continue to avoid fluoro stones if they want to avoid taking the risk of getting one of the "bad" ones. In the case that they purchase a fluorescent stone, they know the grade on the paper is a "worst case scenario" which can only go up in the right lighting if they have an active stone that tends to whiten up.

My main issues are that important aspects or variables of the study conditions weren't communicated entirely and clearly, the sample is fairly small, and the practice of having a single grader report the magnitude of whitening effect is not optimum. I have a problem, therefore, generalizing the findings to all VST and ST blue stones.

 

[sharonp]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Good summary of this thread see comments in bold.

The paper confirms whitening, by a single grader, on a set of stones that were selected in a way we know nothing about. Who selected these stones and was it done at random? Had these stones been examined by Michael prior to the study or did he or someone else choose them prior to the study without any prior examination?

Michael can answer this I don't know, but all should realize VSB are less than <0.5% of diamonds and the ones that are non hazy even less. So I would say getting your hands on VSB diamonds scarcity has to be a factor.

Certainly I agree that the labs should be reporting unenhanced color, and if there is a phenomenon taking place that we need to account for then absolutely change needs to be considered. But if typical lighting environments (not just UV rich sunlight and bright light containing VV) are causing stones to whiten, isn't their predominant "perceived" color the higher color anyway?

The "typical" viewing environment changes dramatically form outside to inside. But I find this to be irrelevant the GIA-GTL grading environment has never represented a true consumer viewing environment and facedown is very different from faceup. For grading the variable of cut needs to be removed from the variables. So color grades represent rarity and set prices but they don't correlate as perfectly to consumer perception of them and never will. Garry and Rockdiamond are claiming that no change is needed because viewing environments contain some UV/VV so its okay for the grading environment to have some even if it makes the color grades of strong fluoro stones less consistent and predictable.

Let me ask this... you've all been around pricescope for a considerable amount of time. Can you recall or link any examples of folks complaining about their fluorescent stones turning yellow and leaving them disappointed?

Karl wrote pages back the bigger problem is the price differential in the colorless and not as easily noticeable range. Can you readily tell the difference between a D and F faceup even if the unlikely happened and you had the opportunity to put two similarly sized and cut diamonds faceup near each other? Maybe facedown some could but the efficient light return in a round readily masks the color differences faceup.

Cases where they complain that they or an appraiser have noticed their stones look more yellow than they should? I sure think that if the labs were getting these wrong by 2-4 grades there would be a considerable amount of unhappy customers who feel let down by the laboratories and voice their opinions online.

Well an example like that would be very rare, according to Cowing's data you would likely need a VSB ( I estimate at <0.5% of diamonds from Bluenile) and there were no examples in the study that touched in the Faint Yellow Range. Further the majority of diamonds are cut into rounds that tend to mask color faceup making it even more difficult for faceup viewers to notice.

Having said all this, and like I said before, I as a consumer would be in favor of returning to the practice of grading in UV free environments. It just makes sense to grade all stones in UV free environments when there are plenty of data to show that these stones whiten when exposed to strong UV.

GIA-GTL claimed they used the practice but they didn't know that the light they were using actually had UV that can cause overgrading.

It just makes sense to grade all stones in UV free environments when there are plenty of data to show that these stones whiten when exposed to strong UV.

The debate seems to be whether more typical environments can also illicit the whitening effect.
Thats not really the focus of the paper but Garry seems to think it is 'important' to this thread.

any people seem to think the answer is yes, and that the stones don't need to be in sunlight or within 7 inches of the UV containing light to whiten. But when it comes to laboratory grading, I say who cares at what point or in which lighting the stones will whiten as long as I know they were all graded with whitening due to fluoro taken out of the equation.

Agreed, except that the paper's solution of diffuser and UV filter hasn't been proven to consistently and conclusively produce the "unwhitened" grade. It would have been a stronger paper if AGSL had graded the diamonds in their DIamond Dock (identical to GIA-GTL)with those filters put on the lights. The grades and observations about any negative effects of diffuser and of reducing the light intensity would be very instructive for determining the feasibility of the solution.

The reason for this is because the whitening due to flouro seems to be an unpredictable event, so all stones should be graded in UV free environments. The stones that show a tendency to whiten can then be sold at a premium and consumers can seek these out if they wish to do so. The seller will know they have something special and price it accordingly. Consumers can choose to continue to avoid fluoro stones if they want to avoid taking the risk of getting one of the "bad" ones. In the case that they purchase a fluorescent stone, they know the grade on the paper is a "worst case scenario" which can only go up in the right lighting if they have an active stone that tends to whiten up.

Agreed

My main issues are that important aspects or variables of the study conditions weren't communicated entirely and clearly, the sample is fairly small, and the practice of having a single grader report the magnitude of whitening effect is not optimum.

I have a problem, therefore, generalizing the findings to all VST and ST blue stones.
Which finding are you referring to? 1)Any significant overgrading 2) 2 - 4 Grades of overgrading for STB and VSB or 3)Either

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

HI Sharon, my responses below yours in blue

Good summary of this thread see comments in bold.

The paper confirms whitening, by a single grader, on a set of stones that were selected in a way we know nothing about. Who selected these stones and was it done at random? Had these stones been examined by Michael prior to the study or did he or someone else choose them prior to the study without any prior examination?

Michael can answer this I don't know, but all should realize VSB are less than <0.5% of diamonds and the ones that are non hazy even less. So I would say getting your hands on VSB diamonds scarcity has to be a factor.


Actually all should realize that given the massive amount of good available for sale VSB diamonds are by no means scarce. Quick search of D-E-F between 1-2ct RBC shows over 150 diamonds. True, that's a very small percentage of the diamonds available, but it also is a pretty substantial number if we're only looking for candidates.

Certainly I agree that the labs should be reporting unenhanced color, and if there is a phenomenon taking place that we need to account for then absolutely change needs to be considered. But if typical lighting environments (not just UV rich sunlight and bright light containing VV) are causing stones to whiten, isn't their predominant "perceived" color the higher color anyway?

The "typical" viewing environment changes dramatically form outside to inside. But I find this to be irrelevant the GIA-GTL grading environment has never represented a true consumer viewing environment and facedown is very different from faceup. For grading the variable of cut needs to be removed from the variables. So color grades represent rarity and set prices but they don't correlate as perfectly to consumer perception of them and never will. Garry and Rockdiamond are claiming that no change is needed because viewing environments contain some UV/VV so its okay for the grading environment to have some even if it makes the color grades of strong fluoro stones less consistent and predictable.

Let me ask this... you've all been around pricescope for a considerable amount of time. Can you recall or link any examples of folks complaining about their fluorescent stones turning yellow and leaving them disappointed?

Karl wrote pages back the bigger problem is the price differential in the colorless and not as easily noticeable range. Can you readily tell the difference between a D and F faceup even if the unlikely happened and you had the opportunity to put two similarly sized and cut diamonds faceup near each other? Maybe facedown some could but the efficient light return in a round readily masks the color differences faceup.
Yes, I have been able to see the difference form a D to an F in the face up position- although it is much easier through the pavilion. About this "problem"- the main problem is for cutters who can't get decent prices for MB/SB/VSB stones, so they have to sell them cheap. You can easily buy a D/VS1 SB for cheaper than a F VS1 inert. This would be two stones equally well cut. I'm missing the problem for buyers- of which I am one daily.

Cases where they complain that they or an appraiser have noticed their stones look more yellow than they should? I sure think that if the labs were getting these wrong by 2-4 grades there would be a considerable amount of unhappy customers who feel let down by the laboratories and voice their opinions online.

Well an example like that would be very rare, according to Cowing's data you would likely need a VSB ( I estimate at <0.5% of diamonds from Bluenile) and there were no examples in the study that touched in the Faint Yellow Range. Further the majority of diamonds are cut into rounds that tend to mask color faceup making it even more difficult for faceup viewers to notice.

Having said all this, and like I said before, I as a consumer would be in favor of returning to the practice of grading in UV free environments. It just makes sense to grade all stones in UV free environments when there are plenty of data to show that these stones whiten when exposed to strong UV.

GIA-GTL claimed they used the practice but they didn't know that the light they were using actually had UV that can cause overgrading.

It just makes sense to grade all stones in UV free environments when there are plenty of data to show that these stones whiten when exposed to strong UV.

The debate seems to be whether more typical environments can also illicit the whitening effect.
Thats not really the focus of the paper but Garry seems to think it is 'important' to this thread.

Not only Garry finds this aspect to be extremely important to consumers. The reason it's become an issue is that Bryan is insisting this can't be happening- solely based on this study.

any people seem to think the answer is yes, and that the stones don't need to be in sunlight or within 7 inches of the UV containing light to whiten. But when it comes to laboratory grading, I say who cares at what point or in which lighting the stones will whiten as long as I know they were all graded with whitening due to fluoro taken out of the equation.

Agreed, except that the paper's solution of diffuser and UV filter hasn't been proven to consistently and conclusively produce the "unwhitened" grade. It would have been a stronger paper if AGSL had graded the diamonds in their DIamond Dock (identical to GIA-GTL)with those filters put on the lights. The grades and observations about any negative effects of diffuser and of reducing the light intensity would be very instructive for determining the feasibility of the solution.

The reason for this is because the whitening due to flouro seems to be an unpredictable event, so all stones should be graded in UV free environments. The stones that show a tendency to whiten can then be sold at a premium and consumers can seek these out if they wish to do so. The seller will know they have something special and price it accordingly. Consumers can choose to continue to avoid fluoro stones if they want to avoid taking the risk of getting one of the "bad" ones. In the case that they purchase a fluorescent stone, they know the grade on the paper is a "worst case scenario" which can only go up in the right lighting if they have an active stone that tends to whiten up.

Agreed

My main issues are that important aspects or variables of the study conditions weren't communicated entirely and clearly, the sample is fairly small, and the practice of having a single grader report the magnitude of whitening effect is not optimum.

I have a problem, therefore, generalizing the findings to all VST and ST blue stones.
Which finding are you referring to? 1)Any significant overgrading 2) 2 - 4 Grades of overgrading for STB and VSB or 3)Either

pfunk- I do agree that you've summarized the essence of the dispute perfectly. Thank you.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

pfunk - In working on this thread, and using my light meter- I can tell you that the light of the sun is pervasive. I mean to say- even if you're not near the window when the sun is shining, the quantity of light you get is exponentially higher than nighttime readings under fairly bright overhead fl lighting.
We have pretty large southern exposure windows.
The large windows and southern exposure allow a phenomenal range of lighting scenarios using blinds, and overhead fluorescent lighting.
I have observed the whitening many times in areas with only reflected sunlight- actually that's the very best lighting to use,
At night, although my fluorescent overhead bulbs are actually quite bright, it's virtually impossible to stimulate this effect.

There's an element in natural sunlight that may bounce off walls- just guessing- but even when you're not in the sun, if there's a window in the room, you may be able to see the diamond's color, and a bit of improvement if its a I-J-K fluoro stone.
In an area with zero sun, even bright fluorescent lighting seems to lack the element that reflected sunlight does in it's effect on diamonds. How many times do people observe diamonds in an area with zero sun?
again, just a guess on why this happens, I'm no scientist, but I know what my eyes have been seeing for 40 years......

 

[pfunk]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Good summary of this thread see comments in bold.

The paper confirms whitening, by a single grader, on a set of stones that were selected in a way we know nothing about. Who selected these stones and was it done at random? Had these stones been examined by Michael prior to the study or did he or someone else choose them prior to the study without any prior examination?

Michael can answer this I don't know, but all should realize VSB are less than <0.5% of diamonds and the ones that are non hazy even less. So I would say getting your hands on VSB diamonds scarcity has to be a factor.

Certainly I agree that the labs should be reporting unenhanced color, and if there is a phenomenon taking place that we need to account for then absolutely change needs to be considered. But if typical lighting environments (not just UV rich sunlight and bright light containing VV) are causing stones to whiten, isn't their predominant "perceived" color the higher color anyway?

The "typical" viewing environment changes dramatically form outside to inside. But I find this to be irrelevant the GIA-GTL grading environment has never represented a true consumer viewing environment and facedown is very different from faceup. For grading the variable of cut needs to be removed from the variables. So color grades represent rarity and set prices but they don't correlate as perfectly to consumer perception of them and never will. Garry and Rockdiamond are claiming that no change is needed because viewing environments contain some UV/VV so its okay for the grading environment to have some even if it makes the color grades of strong fluoro stones less consistent and predictable.

Let me ask this... you've all been around pricescope for a considerable amount of time. Can you recall or link any examples of folks complaining about their fluorescent stones turning yellow and leaving them disappointed?

Karl wrote pages back the bigger problem is the price differential in the colorless and not as easily noticeable range. Can you readily tell the difference between a D and F faceup even if the unlikely happened and you had the opportunity to put two similarly sized and cut diamonds faceup near each other? Maybe facedown some could but the efficient light return in a round readily masks the color differences faceup.

Not all the study diamonds were round, and considering the number of VST blue diamonds that have been graded by GIA over the past few decades, you would expect more complaints if there were numerous 2-4 and even 5 grade discrepancies that are suggested by this small sample size of stones. At least I would think so. And even Michael points out in this paper http://download.cibjo.org/FluorescenceFears.pdf an example of the horrors of overgrading.

Cases where they complain that they or an appraiser have noticed their stones look more yellow than they should? I sure think that if the labs were getting these wrong by 2-4 grades there would be a considerable amount of unhappy customers who feel let down by the laboratories and voice their opinions online.

Well an example like that would be very rare, according to Cowing's data you would likely need a VSB ( I estimate at <0.5% of diamonds from Bluenile) and there were no examples in the study that touched in the Faint Yellow Range. Further the majority of diamonds are cut into rounds that tend to mask color faceup making it even more difficult for faceup viewers to notice.

There are a lot of very well informed consumers who would know what to be looking for and have the ability to recognize it. And I don't believe the diamonds have to fall into the faint yellow, necessarily, in order to be able to recognize the discrepancy. Some folks have great eyes and are well educated, and if an issue with overgrading fluorescent stones was going to be brought up by consumers, pricescope might very well be the place it pops up. Also, quite often the consumer has the ability to view the stone from the profile (nearly unobstructed), not only in the face up position, which would also aid in seeing color.

Having said all this, and like I said before, I as a consumer would be in favor of returning to the practice of grading in UV free environments. It just makes sense to grade all stones in UV free environments when there are plenty of data to show that these stones whiten when exposed to strong UV.

GIA-GTL claimed they used the practice but they didn't know that the light they were using actually had UV that can cause overgrading.

GIA used UV free lighting prior to the transition to the Verilux fluorescent tubes of the DiamondLite though correct?

It just makes sense to grade all stones in UV free environments when there are plenty of data to show that these stones whiten when exposed to strong UV.

The debate seems to be whether more typical environments can also illicit the whitening effect.
Thats not really the focus of the paper but Garry seems to think it is 'important' to this thread.

Many people seem to think the answer is yes, and that the stones don't need to be in sunlight or within 7 inches of the UV containing light to whiten. But when it comes to laboratory grading, I say who cares at what point or in which lighting the stones will whiten as long as I know they were all graded with whitening due to fluoro taken out of the equation.

Agreed, except that the paper's solution of diffuser and UV filter hasn't been proven to consistently and conclusively produce the "unwhitened" grade. It would have been a stronger paper if AGSL had graded the diamonds in their DIamond Dock (identical to GIA-GTL)with those filters put on the lights. The grades and observations about any negative effects of diffuser and of reducing the light intensity would be very instructive for determining the feasibility of the solution.

The reason for this is because the whitening due to flouro seems to be an unpredictable event, so all stones should be graded in UV free environments. The stones that show a tendency to whiten can then be sold at a premium and consumers can seek these out if they wish to do so. The seller will know they have something special and price it accordingly. Consumers can choose to continue to avoid fluoro stones if they want to avoid taking the risk of getting one of the "bad" ones. In the case that they purchase a fluorescent stone, they know the grade on the paper is a "worst case scenario" which can only go up in the right lighting if they have an active stone that tends to whiten up.

Agreed

My main issues are that important aspects or variables of the study conditions weren't communicated entirely and clearly, the sample is fairly small, and the practice of having a single grader report the magnitude of whitening effect is not optimum.

I have a problem, therefore, generalizing the findings to all VST and ST blue stones.
Which finding are you referring to? 1)Any significant overgrading 2) 2 - 4 Grades of overgrading for STB and VSB or 3)Either

Again, it is not any of the "findings" I have issues with. It is the methodology and study design which make me question the validity and generalizability of the findings. Those issues I have already laid out, but the biggest one being that that the magnitude of whitening effect was measured by a single grader without a clear description of how his personal grading practices were conducted. He explained earlier how he stood holding the diamonds at shoulder height or something like that in order to achieve the correct lighting intensity, but I think it would have been wise to clearly explain the procedure used so that others could replicate the study in order to establish that it could be duplicated. We are still not sure what kind of master set was used. These, among others, are things that should have also been laid out in the methods of the study.

Responses added in red above.

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Take a room with artificial light and a window with venetian blinds half closed and you can see that the light from window is way way brighter than the artificial light. The tool I used is a shiny icecream scoop.

The images did not come along - but if you click on the top blue line that says by Garry H (Cut Nut) » 04 Feb 2016 03:26 the images open and show how much light comes from the window
David wrote this:
by Rockdiamond » 23 Mar 2016 01:37
pfunk - In working on this thread, and using my light meter- I can tell you that the light of the sun is pervasive. I mean to say- even if you're not near the window when the sun is shining, the quantity of light you get is exponentially higher than nighttime readings under fairly bright overhead fl lighting.
We have pretty large southern exposure windows.
The large windows and southern exposure allow a phenomenal range of lighting scenarios using blinds, and overhead fluorescent lighting.
I have observed the whitening many times in areas with only reflected sunlight- actually that's the very best lighting to use,
At night, although my fluorescent overhead bulbs are actually quite bright, it's virtually impossible to stimulate this effect.

There's an element in natural sunlight that may bounce off walls- just guessing- but even when you're not in the sun, if there's a window in the room, you may be able to see the diamond's color, and a bit of improvement if its a I-J-K fluoro stone.
In an area with zero sun, even bright fluorescent lighting seems to lack the element that reflected sunlight does in it's effect on diamonds. How many times do people observe diamonds in an area with zero sun? GH comment - how indoor environments can you see the difference between 2 color grades in any place other than with natural light thru windows?
again, just a guess on why this happens, I'm no scientist, but I know what my eyes have been seeing for 40 years......


And I have reposted what I posted on page 1 of this thread.
Argue what you will about various films and things that reduce UV light, but there is an abundant amount of VV coming through my window even on cloudy days.

 

[Karl_K]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

And I have reposted what I posted on page 1 of this thread.
Argue what you will about various films and things that reduce UV light, but there is an abundant amount of VV coming through my window even on cloudy days.

A lot of people work with no windows around and depending on the time of year, location and hours worked a large amount of time at home there will be no sun light.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

And I have reposted what I posted on page 1 of this thread.
Argue what you will about various films and things that reduce UV light, but there is an abundant amount of VV coming through my window even on cloudy days.

A lot of people work with no windows around and depending on the time of year, location and hours worked a large amount of time at home there will be no sun light.

True Karl- but whoever is working or living in a place with no windows would not be able to accurately grade the color of diamonds in those environments.

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

And I have reposted what I posted on page 1 of this thread.
Argue what you will about various films and things that reduce UV light, but there is an abundant amount of VV coming through my window even on cloudy days.

A lot of people work with no windows around and depending on the time of year, location and hours worked a large amount of time at home there will be no sun light.

And insufficient light to tell a D from an I

 

[pfunk]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

And I have reposted what I posted on page 1 of this thread.
Argue what you will about various films and things that reduce UV light, but there is an abundant amount of VV coming through my window even on cloudy days.

A lot of people work with no windows around and depending on the time of year, location and hours worked a large amount of time at home there will be no sun light.

True Karl- but whoever is working or living in a place with no windows would not be able to accurately grade the color of diamonds in those environments.

But why does that matter? Grading should be done accurately at the LAB. Consumers arent looking for color grading errors, or at least they shouldnt have to be. Consumer lighting environments shouldnt really be part of the discussion. If it is known that UV causes whitening, and that there are various types of light that won't cause this whitening, why not just remove the UV component at the lab where the grading is done? Isn't that the safest practice for the consumer?

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

And I have reposted what I posted on page 1 of this thread.
Argue what you will about various films and things that reduce UV light, but there is an abundant amount of VV coming through my window even on cloudy days.

A lot of people work with no windows around and depending on the time of year, location and hours worked a large amount of time at home there will be no sun light.

True Karl- but whoever is working or living in a place with no windows would not be able to accurately grade the color of diamonds in those environments.

But why does that matter? Grading should be done accurately at the LAB. Consumers arent looking for color grading errors, or at least they shouldnt have to be. Consumer lighting environments shouldnt really be part of the discussion. If it is known that UV causes whitening, and that there are various types of light that won't cause this whitening, why not just remove the UV component at the lab where the grading is done? Isn't that the safest practice for the consumer?

Thanks for your reviews Pfunk.
What David and I am saying is that we see grade whitening and GIA's grades appear to be accurate or even conservative when there is enough light to be able to tell face up grade differences.
But I must stress on my behalf - I am focusing mainly on VV not UV, because I think there is plenty of evidence that windows cut out most UV.

 

[Karl_K]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

But I must stress on my behalf - I am focusing mainly on VV not UV, because I think there is plenty of evidence that windows cut out most UV.

I know of one diamond that only responds to some wavelengths of UV and not others and is a gia none that turns blue in sunlight from fluorescence.
One question in my mind is how well does the gia rating predict how a diamond will respond to VV?
Once one starts down this road it opens a lot of questions.

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

But I must stress on my behalf - I am focusing mainly on VV not UV, because I think there is plenty of evidence that windows cut out most UV.

I know of one diamond that only responds to some wavelengths of UV and not others and is a gia none that turns blue in sunlight from fluorescence.
One question in my mind is how well does the gia rating predict how a diamond will respond to VV?
Once one starts down this road it opens a lot of questions.

There is unpredictability in how a fluoro stone will react to different lighting scenarios capable of activating fluorescence. There is great variability in lab reporting of fluorescence to begin with . And GIA regularly reminds us that fluorescence is intended to be an identifying characteristic, not a performance characteristic. As the GIA article that Garry referenced vividly demonstrates, there is a wide variation in the emissions produced by the various fluoro lamps and devices used in the trade and by labs to make the fluorescence assessment. And of course there are multiple defect centers that can enhance, extinguish or combine different levels and colors of fluorescence. There are also different practices from lab to lab in the position that stones are assessed (face-up, table down). Since flouro can be directional, this can change the observation (and the reporting) dramatically in certain cases.

This variability is the exactly why, as Pfunk sums up succinctly, that from a consumer perspective the lab color grade should accurately relflect the body color of the diamond when not altered by fluorescence. And this is the essence of the conclusions of the Cowing study.