Article Over Grading of Blue Fluorescent Diamonds Revisited

[Rockdiamond]

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.

Karl- from the sound of it, GIA made an error on the FL grading of your stone.
I have seen this happen on a limited number of occasions.

 

[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.

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?

This has been an amazing discourse, and your contribution invaluable Pfunk.
To expand on what Garry said and further put this flawed study in context: Trying to determine accuracy of GIA color grading using 15 diamonds completely invalidates the findings based on statistics, and the variation possible in diamonds.

We are not sure of the exact methodology of how GIA color grades diamonds. DO they use a machine? What's the exact distance form the bulb? And GIA is not going to be forthcoming about this.
What we can accurately describe is GIA grading results.
Although Garry and I have disagreed on countless occasions in the past, we are in total agreement here. Given the physical limitations, GIA is doing a very good job issuing color grades on diamonds FL or inert.
Putting aside Garry and my statements, we have no other corroboration a problem exists. Given the amount of time PS member/readers spend discussing the finer points of diamonds here, we would have heard of people having issues, if those issues existed.
The only trade member who is citing this study is not even using actual diamonds, rather relying on the "science" in the report- which is flawed.
Bottom line- if it ain't broke, don;t fix it.

 

[sharonp]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

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.

GIA grades are accurate or conservative compared to what?
What does any of this have to do with faceup differences? (grading is done facedown as you know)

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.

Windows coatings don't cut out UVA (320 - 400nm) which is what was being measured as UV in the Cowing Study and GIA published in 2008 to be contained in the Verilux tubes used in the current GIA-GTL diamond dock.



How can GIA-GTL grades be conservative when their light intensity profile for the lights they are using in the Diamond Dock clearly shows strong peaks in the UV and VV that are not filtered.

Your comments just baffle me, they are ambiguous, I can't make sense of your argument.

 

[sharonp]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

This has been an amazing discourse, and your contribution invaluable Pfunk.
To expand on what Garry said and further put this flawed study in context: Trying to determine accuracy of GIA color grading using 15 diamonds completely invalidates the findings based on statistics,

Do you even have any background in statistics? Do you even know what a null hypothesis is? Did Michael have enough data to disprove the null hypothesis?

We are not sure of the exact methodology of how GIA color grades diamonds.

We've been through this earlier in this thread when I pointed you to the GIA 2008 article , interestingly enough AGSL and GIA-GTL have almost identical color grading and the market pricing has proven this for years. To use your favorite argument where are all the complaints and discounting of AGSL grades versus GIA? The author has had access to the AGSL grading lab setup (permission from director Peter Yantzer) yet YOU not COWING still has no clue exactly how GIA-GTL and AGSL grades.

DO they use a machine? What's the exact distance form the bulb? And GIA is not going to be forthcoming about this.

http://www.gia.edu/gems-gemology/winter-2008-color-grading-d-to-z-diamonds-king

All answered in that article which is a free download, 1) Yes but it does not replace visual human graders. 2) Distance 8 - 10"

The real bottom line, your repeated self aggrandizing statements over dozens of postings in this thread have proven nothing except that you know how to turn off yet another trade professional from participating here.

Yes there are weaknesses in Cowing's study not ones that invalidate its conclusions but ones that should be examined in future. Instead of encouraging him to participate here more, and make his study more robust you've done the opposite, you've scared away consumers from participating (there have only been two of us) and without them the author really has no incentive to participate.

 

[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.

Karl- from the sound of it, GIA made an error on the FL grading of your stone.
I have seen this happen on a limited number of occasions.

nope, go back to the first or second page and reread. It is indeed a strange one.
What I don't know if it is common or not.

 

[Rockdiamond]

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.

Karl- from the sound of it, GIA made an error on the FL grading of your stone.
I have seen this happen on a limited number of occasions.

nope, go back to the first or second page and reread. It is indeed a strange one.
What I don't know if it is common or not.

I'm pressed for time Karl- can't go back to re-read now-.
If you took your diamond, held it in a darkened areas and shine a UV light on it, does it glow?

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Hi Sharon,
Thanks again for making it interesting.
I have no background in statistics. I do have friends that are, and I'll be getting some schooling on it later.....but it sounds as though you do. Here's my consideration, please explain what I'm missing.

There's almost one million diamonds listed on Rapnet that have been graded by GIA.
Please explain how a 15 stone sample, ( of which we have no information how they were selected) provides any meaningful data in a general sense?

 

[michaelgem]

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?

Thank you, Pfunk, for showing with this question that despite all these 10 pages of interaction, the message that the consumer would be best served by the labs grading in lighting that does not stimulate grade whitening amounts of blue fluorescence has not been lost, at least not on you. This unenhanced, stable color grade due to the diamond's selective wavelength absorption would then only get better in the presence of daylight. And the consumer would not be paying for an elevated color grade that requires UV stimulation of blue fluorescence in the DiamondDock or daylight to be seen.

A lot of the posts make you wonder if the following conclusions were read:

Restoration of grading for the diamond’s true color can be accomplished by the use of polycarbonate plastic such as Lexan. Polycarbonate is an effective and inexpensive filter that blocks the UV in fluorescent lighting, removing its grade whitening effect on blue fluorescent diamonds. Removal of the grade whitening effect due to deep violet wavelengths has also been shown to be accomplished by keeping the visible light intensity below 400fc. Another solution is the use of white LED technology. LED lighting provides inherently UV-free grading light avoiding noticable stimulation of fluorescence.

Either solution is consistent with the trade’s historical desire that diamonds be examined for their unenhanced “true body color”.

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

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

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

Thirdly, blue-fluorescent diamonds could be shown to whiten from their graded color, and sometimes appear blue-white in natural daylight. Promoting this advantage in comparison with non-fluorescent diamonds of similar grade would return the marketing advantage to blue fluorescent diamonds that they once enjoyed.

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

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

We do agree on one thing Michael- thank you pfunk!!!
I read and understand the conclusions you refer to- yet I do not agree.
Back to why the study is flawed:
Here's two vital considerations pfunk brought up a page back. Of course I have been asking these questions as well- all due respect Michael after 10 pages it really seems you don't want to or can't respond to these considerations:

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.

Simply put- if we have no independent verification of your grades, how can we trust them? Lest you think I'm singling you our Michael, the same would hold true if any single grader was making these claims.
Then the issue of sample size, and selection.
Please speak directly to these considerations.

You're claiming there's a problem- and that GIA is incorrectly grading diamonds.
To back up such a claim, you really need more and better evidence.

We do agree that fl stones are unfairly judged by consumers causing a diminution of prices- but your study is not going to change that.
In fact, it's that aspect that means consumers are NOT getting ripped off due to GIA grading practices- they are paying less for FL stones regardless of if they are actually worth less.

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

If you have read this deep into this thread, you will probably not mind the lengthiness of the following post.

I have enormous respect and admiration for the GIA. I was trained by them and have had the pleasure to meet so many outstanding people who are or have been part of the organization over a career that has now spanned four decades. I understand why they are relied upon by trades people and consumers all over the world. But they are not infallible and the methodologies and conclusions of their studies are not necessarily beyond question.

There have been some criticisms here of the sample size and methodology of the Cowing study, not necessarily on the conclusions reached based upon the results gathered. At the same time at least one poster has suggested that GIA is the only authority capable of doing a valid study of this nature. In this regard I think it is instructive to take a look at the methodology and conclusions of the 24-stone 1997 GIA study that has been widely referenced in the trade. The basic take-aways that are commonly drawn from this study are that 1) that it is extremely rare for a fluorescent diamond to be hazy and 2) that blue fluorescence generally improves the appearance of diamonds. Because GIA enjoys enormous respect, and because they have eminently qualified scientists behind their work, people do not seem to give their work nearly as much critical scrutiny as I see happening here. So let’s take a closer look at the details and see if other conclusions might be reached on the basis of this study.

http://www.gia.edu/gems-gemology/winter-1997-fluorescence-diamonds-moses

A couple of things stand out to me in this study and I would be interested to see other opinions on these issues. I know we have contributors here that have expertise in methodology and statistical analysis of studies of this nature.

The thing that most strikes me is the fact that one of the groups of observers, arguably the most important from the perspective of the consumer, consisted of “average observers” – those with no lab or trade experience in grading diamonds. Because the results of this group were inconclusive, those results were apparently removed from the overall analysis. It seems from my reading that the conclusions of the study were based upon an aggregate statistical analysis, and therefore one of only the lab/trade observers. And of the 5 lighting scenarios in the survey 4 had significant UV/VV components.

Here are a few interesting quotes from the article:

The response of a diamond to the concentrated radiation of an ultraviolet lamp is mentioned as an identifying characteristic (rather than a grading factor) on quality-grading reports issued by most gem-testing laboratories.

Although we would have preferred a larger sample of diamonds,we felt that this initial study should focus on controlling those other variables that could affect appearance, leaving fluorescence as the variable to be studied. Despite the large number of blue fluorescent diamonds that were available, potentiall yinfluential factors such as size, proportions, polish, symmetry, and clarity considerably narrowed our final selection.

Recognizing that some highly fluorescent diamonds might have a slightly different color appearance when viewed under light sources with differing UV content, Shipley and Liddicoat (1941) emphasized the importance of controlled lighting conditions for consistent color grading of faceted diamonds.

Because some observers brought their own trade practices to the experiment,and others had no prior experience with some of the environments, we did not ask all observers to make observations in each type of environment. Nor do we have equal numbers of observations for each group of observers and viewing environment. However, we did ask four observers (three Laboratory Graders and one Trade Observer) who had both laboratory and extensive trade experience to look at the diamonds in more than one viewing
environment.

For the average observer,meant to represent the jewelry buying public, no systematic effects of fluorescence were detected.

For the observers in this study, the effect of blue fluorescence on color appearance and transparency in
colorless to faint yellow diamonds was subtle. In fact, our results indicate that Average Observers
could not make the fine distinctions sought in this study.

One interesting aspect of this study was that the nontrade observers could not make meaningful distinctions. For this group,which would be considered most representative of the jewelry-buying public, fluorescence had no overall effect on color appearance or transparency.

We found that the observations by the Trade Graders and Trade Observers showed trends similar to the observationsby Laboratory Graders. However, observations by Average Observers were randomly distributed (that is, even in a color set and viewing environment where trained Laboratory Graders detected a trend in stone color or transparency, average observers did not). Therefore, the results for Average Observers were excluded from the remainder of the analysis. It is apparent that the Average Observers were not able to consistently discriminate any fluorescence-related effects in the viewing environments most similar to those in which jewelry is purchased and worn.

Some of the questions that come to my mind in this 24 stone study are:
Were the color grades of the diamonds to start with verified as accurate, controlling for the presence of UV VV stimulation during the grading? (The pictures of the diamonds do seem to vary in color).

If the results of the average observers were removed from the analysis, did that make the trends identified by the trade/lab observations more well defined and therefore seem more statistically significant?

What are the implications for the objectivity of the study and/or conclusions drawn from the data with respect to the study’s financial support from a sight holder?

I have no doubt that other questions might occur to those with more experience in this sort of analysis. And I bring these issues up not to disparage the GIA study, after all they call it a “contribution” to understanding fluorescence (which I definitely think it is) not the “definitive work” on fluorescence. And they are forthcoming about assumptions and limitations of the study as well as transparent about the parties involved in conducting and supporting the study.

I think the Cowing study is also a contribution to understanding a potential pitfall of lab practice in regards to color grading of this important subset of gem diamonds. I see the Cowing study as both consumer advocacy as well as advocacy for the specialness of fluorescent diamonds.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Bryan- say we all agreed that the study's conclusions were correct.
If consumers believe that GIA is misgrading fluoro diamonds, wouldn't that drive the price of such stones even lower?
I think we can all agree that GIA isn't going to change their current procedures due to this article.
Given all that, in your opinion how much more should SB MB VST stones be discounted under GIA current practices?

Just today a consumer was asking about deciding between a G Fluoro versus an I
Here

 

[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?

This has been an amazing discourse, and your contribution invaluable Pfunk.
To expand on what Garry said and further put this flawed study in context: Trying to determine accuracy of GIA color grading using 15 diamonds completely invalidates the findings based on statistics, and the variation possible in diamonds.

We are not sure of the exact methodology of how GIA color grades diamonds. DO they use a machine? What's the exact distance form the bulb? And GIA is not going to be forthcoming about this.
What we can accurately describe is GIA grading results.
Although Garry and I have disagreed on countless occasions in the past, we are in total agreement here. Given the physical limitations, GIA is doing a very good job issuing color grades on diamonds FL or inert.
Putting aside Garry and my statements, we have no other corroboration a problem exists. Given the amount of time PS member/readers spend discussing the finer points of diamonds here, we would have heard of people having issues, if those issues existed.
The only trade member who is citing this study is not even using actual diamonds, rather relying on the "science" in the report- which is flawed.
Bottom line- if it ain't broke, don;t fix it.

David I never called this a flawed study - it has a lot of great info in it that makes this discussion possible and better.
I do not agree with much of the findings and some methods and think it should be expanded on, and I hope Michael will agree to that

 

[Garry H (Cut Nut)]

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.

Yes Michael, the 2013 GIA study showed and discussed how different combinations of color centers or missing carbon atoms and imurities can react together and cause all sorts of weird results.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

You're right Garry- that was a poor choice of words. My apologies to Michael.
I also hope we can further the discussion.
Michael's input has indeed made this a far more valuable discourse.

 

[sharonp]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

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

Michael, you proposed two ways of solving this problem. Increasing the distance to the lights (your solution 7) which you found yourself even with sufficient intensity had issues with the quality of the light, such that you had to use paper to block glare. I asked you questions about that, back many pages ago about if that would change the intensity of the light at the diamonds, given that you were only allowing light through a small opening.

The second solution the Lexan Filter and Diffuser, its a pity that you didn't grade diamonds under these conditions in a Diamond Dock and compare it to your source 7. You could have used Source 3 with a UV filter and diffuser or even better have AGSL graders grade them again in their box with the Lexan filter and diffuser.

I feel that that the study would be more conclusive if you had actually applied your preferred solution to obtain the 'True' grades for the VSB and SB diamonds.

 

[michaelgem]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

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

Sharon reminds Michael: You proposed two ways of solving this problem. Increasing the distance to the lights (your solution 7) which you found yourself even with sufficient intensity had issues with the quality of the light, such that you had to use paper to block glare. I asked you questions about that, back many pages ago about if that would change the intensity of the light at the diamonds, given that you were only allowing light through a small opening.

Sharon, you and others came away with the misimpression that I had any particular difficulty in grading the true unenhanced body color that exists under most all forms of light at typical viewing distances of about 3 or more feet.

Let's take another shot at this:

Source 7 was Northern daylight balanced fluorescent lighting mounted in an 8ft ceiling. I stood under it holding the tray of diamond masters and the diamond to be graded, viewing them at about a 10 inch close focusing distance, which was about three feet from the tubes.

The difficulty in grading at 3ft is the same as grading at 7 inches in the DiamondDock. The diamonds' reflections and sparkle at the tray in the DiamondDock are an impediment to judging body color, which is why there is a tendency to raise the diamonds up closer to the tubes where the light is more diffuse.

The solution to eliminating the reflections and sparkle is to create a diffuse lighting environment at the diamonds like that present very close to the tubes. That was accomplished by both illuminating and viewing the diamonds through the opening of a folded white card at the 3 foot distance. This technique produced more than sufficient light that uniformly illuminated the diamonds. This arrangement acted like an integrating sphere, which uniformly diffuses illumination without diminishing or blocking the light as do typical diffusers. The method cuts out the reflections and sparkle, and enables an accurate read of the unenhanced true body color.

There were no remaining issues or difficulty in grading this way. In fact, employing this technique would improve grading at the seven inch distance in the DiamondDock where similar reflections and glare hamper observation of diamond body color.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

We do agree on one thing Michael- thank you pfunk!!!
I read and understand the conclusions you refer to- yet I do not agree.
Back to why the study is flawed:
Here's two vital considerations pfunk brought up a page back. Of course I have been asking these questions as well- all due respect Michael after 10 pages it really seems you don't want to or can't respond to these considerations:

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.

Simply put- if we have no independent verification of your grades, how can we trust them? Lest you think I'm singling you our Michael, the same would hold true if any single grader was making these claims.
Then the issue of sample size, and selection.
Please speak directly to these considerations.

You're claiming there's a problem- and that GIA is incorrectly grading diamonds.
To back up such a claim, you really need more and better evidence.

We do agree that fl stones are unfairly judged by consumers causing a diminution of prices- but your study is not going to change that.
In fact, it's that aspect that means consumers are NOT getting ripped off due to GIA grading practices- they are paying less for FL stones regardless of if they are actually worth less.

Michael- even putting aside the fact you're claiming to be color grading diamonds in a manner that completely goes against current grading methods- or even because of that aspect - why won't you simply respond the the considerations pfunk has raised here. Why should anyone trust a single uncorroborated opinion?
If anyone else published a study claiming GIA is issuing grades that are 4 shades incorrect would you not expect them to prove this by (at the very least) having a second opinion?
How were the stones selected? Did you see them prior to the study?
Yes it is frustrating how you have continually answered any posts agreeing or accepting the incorrect conclusions yet avoided directly responding to these questions for 10 pages.

 

[sharonp]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Sharon, you and others came away with the misimpression that I had any particular difficulty in grading the true unenhanced body color that exists under most all forms of light at typical viewing distances of about 3 or more feet.

I believe the grades you published in your paper for Source 7 on their face, however I would want to see those same stones graded in the Diamond Dock with your suggested UV and diffuser to see if the results are the same.

I don't beleive the GIA-GTL method uses the paper as you have done and any deviation from their methods creates doubt and uncertainty about the general applicability of the results to all SB and VSB diamonds.

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Another attempt to divert the discussion towards solutions:

Grade whitening or yellowing that customers can see is what interests me, and if we really are about consumer protection and benefits - then we should be able to prove it as a positive or a negative. Yes? No?

I saw recently a medium fluoro yellow 2ct rd at the HK trade fair - it showed a huge face up grade drop in dim lighting - more so away from the desk lamps. The ceiling in the fair was half a mile high and it had Costco Walmart type lighting.

So, my question is, if fluoro yellow causes visible grade drops, why can't blue fluoro cause grade whitening?
And why do hundreds of my customers see it in side by side comparisons?

 

[sharonp]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Another attempt to divert the discussion towards solutions:

'Solutions' are a major part of Michael's paper unlike your consumer opinion poll.

Garry why don't answer questions and quotes of your posts https://www.pricescope.com/communit...evisited.219341/page-10#post-4010406#p4010406
I tried to follow you argument and you didn't bother to answer.

 

[sharonp]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Hi Sharon,
Thanks again for making it interesting.
I have no background in statistics. I do have friends that are, and I'll be getting some schooling on it later.....but it sounds as though you do. Here's my consideration, please explain what I'm missing.

There's almost one million diamonds listed on Rapnet that have been graded by GIA.
Please explain how a 15 stone sample, ( of which we have no information how they were selected) provides any meaningful data in a general sense?

My thesis supervisor was a grumpy old british man in his 70s, impeccable English and grammar and on nitpicking the smallest little thing on sentence structure for publishing my research. Unfortunately for me once he was tenured he did very little of significant research or publishing in the last decade or probably in his entire career.

He was excellent at being the self proclaimed editor on the research and lectures from visiting professors even those far outside his area. He was great at setting ridiculously impractical standards in order to validate their work. In that way in his mind he could always put down their work and elevate himself. None of their research was ever good enough for him yet it was often far superior to his own.

You posts remind me a lot of this supervisor, while I am sure in your mind a huge 1500 stone dataset being graded by teams of GIA-GTL graders, the GIA-GTL lab using filtered and unfiltered light in the Diamond Dock might be the only standard you would accept, it is a wildly unrealistic standard and is nowhere near what any reasonable reader should take in considering Michael's work.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

HI Sharon,
There's simply no evidence of overgrading by GIA, and in fact scads of real life experience I have to contradict Michael's claim of overgrading.
Lest you think I'm just being a "spoiler", I am committed to consumer education. I've spend the a large amount of time over the past 17 years educating consumers on the perils of misgrading- by EGL. I've shown real life examples of stones overgraded by as much as 7 grades. By making a claim GIA is doing something wrong, Michael's conclusions do the opposite of educating the consumer.
Given that my position is that GIA is doing this correctly, the solutions I have been thinking of would be to substantiate my position, and show that GIA grading is, by and large, fair.
I have been thinking a lot about possible solutions.

First of all, instead of randomly ( who knows how random) diamonds, I think it would make more sense for people who handle diamonds daily and participate here to actively look for difficult cases.
We have one right now- GIA graded G, strong blue.
The stone is a bitch to grade. In "normal" lighting- that is to say, a room with natural and overhead fl lighting, it looks like an E. In a light box- which seems to have less UV ( never tested) the color goes down to looking like a low G.
Consmers are going to be loking at the stone in "normal" lighting. How should we grade the diamond?
In my opinion the best we can do is compromise


,

 

[sharonp]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

HI Sharon,
There's simply no evidence of overgrading by GIA, and in fact scads of real life experience I have to contradict Michael's claim of overgrading.

Proof of what? how? and how would you prove or disprove that?

I could care less about your anecdotal 'evidence' or your 'experiments' or years of 'experience'. No consumer views their diamonds 7 inches away from a powerful light containing UV, unset facedown in a tray like GIA-GTL does when they do color grading. Michael's paper is and will always be far superior to any 'experiments' you will ever do on this topic.

Somehow in one month of this time wasting banter (of which I have become a foolish participant), neither you and Garry have ever faced the fact that lab grading environments have NEVER and likely will NEVER match consumer viewing environments.

It is ridiculous that two of you equate the ambiguous notion that because their is undefined and variable UV and VV all around us so therefore GIA-GTL having high intensity UV and VV seven inches from the diamond in their grading environment somehow makes sense and is 'correct'.

This is the argument the two of you have been poorly articulating over and over again, that along with your petty challenges to Michael's methodology and credentials have been keeping this thread going far too long.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

HI Sharon,
There's simply no evidence of overgrading by GIA, and in fact scads of real life experience I have to contradict Michael's claim of overgrading.

Proof of what? how? and how would you prove or disprove that?

Since Michael is the one making a claim that GIA is not correctly grading diamonds, he would need to validate that claim, and he has not done so.

I could care less about your anecdotal 'evidence' or your 'experiments' or years of 'experience'. No consumer views their diamonds 7 inches away from a powerful light containing UV, unset facedown in a tray like GIA-GTL does when they do color grading. Michael's paper is and will always be far superior to any 'experiments' you will ever do on this topic.

Somehow in one month of this time wasting banter (of which I have become a foolish participant), neither you and Garry have ever faced the fact that lab grading environments have NEVER and likely will NEVER match consumer viewing environments.
Regardless of exactly how they do it, GIA needs to do is issue grades accurate to consumers- and they are doing that. Also to the point- GIA is not going to change their methods because Michael thinks they should- nor will they reveal all the specific of their grading methods, making that aspect of the discussion acedemic

It is ridiculous that two of you equate the ambiguous notion that because their is undefined and variable UV and VV all around us so therefore GIA-GTL having high intensity UV and VV seven inches from the diamond in their grading environment somehow makes sense and is 'correct'.

This is the argument the two of you have been poorly articulating over and over again, that along with your petty challenges to Michael's methodology and credentials have been keeping this thread going far too long.

Thanks again for continuing the discussion Sharon.
Clearly Michael has no response the the critical questions about grading methodology and review by other graders, and stone selection.
All due respect, but why are you accepting Michael's opinion of GIA grades at face value, yet almost every statement Garry or I make is suspect?
Besides you, no one is defending the conclusions, which truly have been de-bunked here IMO.

The part that's NOT academic for me- GIA is doing a good job- and it's simply a disservice to consumers to try and convince them GIA is doing something wrong.

The SB stone I referred to above is approx 20% less than a similar inert stone. As I have before, I ask- how is this negatively impacting consumers again?

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

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.

GIA grades are accurate or conservative compared to what?
What does any of this have to do with faceup differences? (grading is done facedown as you know)

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.

Windows coatings don't cut out UVA (320 - 400nm) which is what was being measured as UV in the Cowing Study and GIA published in 2008 to be contained in the Verilux tubes used in the current GIA-GTL diamond dock.



How can GIA-GTL grades be conservative when their light intensity profile for the lights they are using in the Diamond Dock clearly shows strong peaks in the UV and VV that are not filtered.

Your comments just baffle me, they are ambiguous, I can't make sense of your argument.

Sorry Sharon, I missed this one.
I have attached an earlier image I made though that addresses some part of the issue. And refer again to the article http://www.gia.edu/gems-gemology/summer-2013-luo-fluorescence-optical-defects
The evidence from Michaels and earlier AGS testing showed a big drop off in UV from windows. My 415 nm lens filter shows there is however plenty of 415 available and we know that is an important part of VV excitation (good, good, good vibrations).
Did i miss anything else?

 

[sharonp]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

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.

GIA grades are accurate or conservative compared to what?
What does any of this have to do with faceup differences? (grading is done facedown as you know)

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.

Windows coatings don't cut out UVA (320 - 400nm) which is what was being measured as UV in the Cowing Study and GIA published in 2008 to be contained in the Verilux tubes used in the current GIA-GTL diamond dock.



How can GIA-GTL grades be conservative when their light intensity profile for the lights they are using in the Diamond Dock clearly shows strong peaks in the UV and VV that are not filtered.

Your comments just baffle me, they are ambiguous, I can't make sense of your argument.

Sorry Sharon, I missed this one.
I have attached an earlier image I made though that addresses some part of the issue. And refer again to the article http://www.gia.edu/gems-gemology/summer-2013-luo-fluorescence-optical-defects
The evidence from Michaels and earlier AGS testing showed a big drop off in UV from windows. My 415 nm lens filter shows there is however plenty of 415 available and we know that is an important part of VV excitation (good, good, good vibrations).
Did i miss anything else?

Garry I'm not questioning the data you posted or in the 2008 paper, but what is your point? Once again I am left guessing if you are making the argument that because their is undefined and variable intensity VV around us that GIA-GTL should keep intense VV 7 inches from diamonds and that is somehow the 'correct' way to grade to match some consumer viewing environments.

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

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.

GIA grades are accurate or conservative compared to what?
What does any of this have to do with faceup differences? (grading is done facedown as you know)

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.

Windows coatings don't cut out UVA (320 - 400nm) which is what was being measured as UV in the Cowing Study and GIA published in 2008 to be contained in the Verilux tubes used in the current GIA-GTL diamond dock.



How can GIA-GTL grades be conservative when their light intensity profile for the lights they are using in the Diamond Dock clearly shows strong peaks in the UV and VV that are not filtered.

Your comments just baffle me, they are ambiguous, I can't make sense of your argument.

Sorry Sharon, I missed this one.
I have attached an earlier image I made though that addresses some part of the issue. And refer again to the article http://www.gia.edu/gems-gemology/summer-2013-luo-fluorescence-optical-defects
The evidence from Michaels and earlier AGS testing showed a big drop off in UV from windows. My 415 nm lens filter shows there is however plenty of 415 available and we know that is an important part of VV excitation (good, good, good vibrations).
Did i miss anything else?

Garry I'm not questioning the data you posted or in the 2008 paper, but what is your point? Once again I am left guessing if you are making the argument that because their is undefined and variable intensity VV around us that GIA-GTL should keep intense VV 7 inches from diamonds and that is somehow the 'correct' way to grade to match some consumer viewing environments.

In my experience clients notice a face up grade improvement in my store where for example a GIA F Strong Blue appears whiter and brighter than a D of the same size and cut. They make this distinction face up with my stock which is entirely GIA H to D for loose for diamonds Med but especially Strong and in settings. The lighting today is a mix of very high LED and some fluoro tubes and daylight facing windows with a wide verandah and 4-5 yards from the windows (The LED's replaced Halogens about 2 years ago).

So I consider GIA are grading conservatively. Can you think of anything more specific I can add Sharon?

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

HI Sharon, if we can move away from attack mode, and into solution mode....
What would be your suggestion for how to select the stones for a study?
How many graders should assess the diamonds to give a more balanced and objective grading process?

 

[Karl_K]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

HI Sharon, if we can move away from attack mode, and into solution mode....
What would be your suggestion for how to select the stones for a study? hundreds would be a good start
How many graders should assess the diamonds to give a more balanced and objective grading process?

I would rather see machines grading color but the most critical step is going to be identifying the ones the machine can not grade accurately and qc checking.
I also feel that humans could grade clarity without being near the diamond with the same or better accuracy as today and use that to teach AI how to grade. After a few years you may have a pretty good clarity grading AI or you may not.
Again the key is kicking out the ones it can't grade for human grading.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Hundreds would be great Karl- but my question is: How do we select which hundred stones we're going to use.
For example, if we wanted to test for average height and we used an NBA team the result would be quite a bit different than if we chose little people.


My thought is that by trying to find the stones that are harder to grade, we'd get a better understanding if there is actually a problem