Article Over Grading of Blue Fluorescent Diamonds Revisited

[michaelgem]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Your observation that "Removing UV alone had negligible effect for Strong and Medium Fluoro diamonds in the presence of strong white light" indicates the importance of the contribution to fluorescence of excitation from the 405nm deep visible violet mercury vapor peak present in all fluorescent lighting.

I don't know how good your lexan filter is but assuming it worked to reduce UV to negligible through the entire longwave spectrum, the whitening difference between Source 1 filtered for UV and Source 7 should be from the VV. One cannot just eliminate only VV wavelengths(unless you wanted to use red light), you have to attenuate the light of all visible wavelengths to reduce the VV. Does the diffuser reduce the quality of light as well?

By requiring grading at 7 (8.5) inches from the Verilux tubes in the DiamondDock, GIA not only ameliorated the color enhancement caused by blue fluorescence due to UV, but also that caused by the Visible Violet through reduction in light level to around 350fc from the grade enhancing 600fc typical in the DiamondLite and close to the GIA Microscope Lamp.

Well they did, but not by a significant amount. Comparing Source 1(GIA Diamondlite unfiltered) to Source 2(GIA Diamond Dock)

Sample 3 and 4 reduced by two grades
Samples 2 and 9 reduced by 1 grade.
Sample 23 reduced by 1 grade but this wasn't attributed to Fluoro as the sample had none.

The rest of the 20 samples showed no change from Diamondlite conditions to Diamond Dock. Only the VSB diamonds(not all) showed a significant difference.

Michael: Your observation that "Removing UV alone had negligible effect for Strong and Medium Fluoro diamonds in the presence of strong white light" indicates the importance of the contribution to fluorescence of excitation from the 405nm deep visible violet mercury vapor peak present in all fluorescent lighting.

Sharon: I don't know how good your lexan filter is but assuming it worked to reduce UV to negligible through the entire longwave spectrum, the whitening difference between Source 1 filtered for UV and Source 7 should be from the VV.



Michael: You are right. Both methods, the lexan filter and the 3ft distance, reduce the UV to less than 1 uWatt, but only the distance method reduces the visible light intensity below the necessary 400fc to avoid grade whitening. That is the reason for the necessity, when grading close to the fluorescent lighting, for the white diffuser which attenuates the visible light including the VV wavelengths to under 400fc.

Sharon: One cannot just eliminate only VV wavelengths(unless you wanted to use red light), you have to attenuate the light of all visible wavelengths to reduce the VV. Does the diffuser reduce the quality of light as well?

Michael: White diffusers like the one on the GIA microscope light reduce the visible light intensity by absorbing energy equally across all visible wavelengths including the visible violet. If it did not the quality/color of the light would change. (For example, if the VV and blue energy were attenuated more, the light quality would become yellowish, as happens in Cape Series type 1A diamonds.) The white plastic diffuser acts to lower light intensity similarly to a neutral density filter in photography, it absorbs/reduces all visible energy equally maintaining the color/quality/color temperature of the light.

Michael: By requiring grading at 7 (8.5) inches from the Verilux tubes in the DiamondDock, GIA not only ameliorated the color enhancement caused by blue fluorescence due to UV, but also that caused by the Visible Violet through reduction in light level to around 350fc from the grade enhancing 600fc typical in the DiamondLite and close to the GIA Microscope Lamp

Sharon: Well they did, but not by a significant amount. Comparing Source 1(GIA Diamondlite unfiltered) to Source 2(GIA Diamond Dock)
Sample 3 and 4 reduced by two grades
Samples 2 and 9 reduced by 1 grade.
Sample 23 reduced by 1 grade but this wasn't attributed to Fluoro as the sample had none.

The rest of the 20 samples showed no change from Diamondlite conditions to Diamond Dock. Only the VSB diamonds(not all) showed a significant difference.

Michael: Your right except for the difference between Diamondlite conditions to AGSL's Diamond Dock.
Recall from the article: Looking at the scatter plot of the ‘Strong Blue’ diamonds #6 to #10 a quite consistent two grade whitening is evident in the unfiltered DiamondLite as well as in the DiamondDock standard Verilux lighting used in the GIA and the author’s grading, compared with the grades obtained in UV-free light. AGSL’s grading of these ‘Strong Blue’ diamonds differed, obtaining on average only one grade of whitening in their DiamondDock lighting.

The conclusion was: Judging from this limited sample size, the change in lighting from the DiamondLite to the DiamondDock, while clearly reducing the likely amount of over grading in ‘Very Strong Blue’ diamonds, appears to result in a less consistent reduction in the ‘Strong Blue’ fluorescent diamonds. The same can be said for the less consistent reduction seen in the half to one grade whitening typically seen in the ‘Medium Blue’ diamonds in the unfiltered DiamondLite.

Besides human grading variability, this lack of consistency is likely related to the stated wide allowed range in strength of UV and visible light in the unfiltered Diamond Dock lighting. The light intensity measured at the tray in the AGSL DiamondDock was weaker at 230fc compared to 350fc measured at the same 7inches in the same Verilux tubes (obtained with the DiamondDocks that AGSL bought from GIA). This is a good illustration of the inevitable inconsistency that results when grading in lighting with fluorescence enhancing amounts of UV and VV.

This all led to the conclusion: A more practical way to eliminate UV in grading illumination, and at the same time not noticeably affect the visible spectrum is filtration by polycarbonate plastic, such as Lexan or Makrolon. As shown in Figure 6, polycarbonate is an effective and inexpensive filter to remove UV below 385 nm. At the same time there is negligible change to the visible spectrum that could affect grading the D-Z tints of yellow in diamond.

To reduce fluorescence stimulated by visible violet, an equally practical and inexpensive solution is the use of flat-white plastic diffusers which attenuate violet and all visible wavelengths equally. Below 400 fc or about 4000 lux, the reduced amount of visible violet was found to not excite noticeable fluorescence, and the diamond’s color is unaffected. Such white diffusers have the additional feature of reducing spectral reflections and glare. They were employed on GIA microscope lights (Figure 10) for this purpose and to filter UV. (Note that although they did a good job of reducing reflections and glare, they did not reduce the UV or the light intensity enough to avoid all grade whitening fluorescence.)

Michael is this your opinion or a fact based on evidence and testing?

Michael: White diffusers like the one on the GIA microscope light reduce the visible light intensity by absorbing energy equally across all visible wavelengths including the visible violet. If it did not the quality/color of the light would change. (For example, if the VV and blue energy were attenuated more, the light quality would become yellowish, as happens in Cape Series type 1A diamonds.) The white plastic diffuser acts to lower light intensity similarly to a neutral density filter in photography, it absorbs/reduces all visible energy equally maintaining the color/quality/color temperature of the light.

This is all fact understood through spectrum analysis and colour science. The yellow tint in cape series type 1A diamonds is the result of the N3 center's greater attenuation of wavelengths in the violet and deep blue. When we observe that a filter like the one on the GIA microscope light does not change the light's quality/colour it is because all wavelengths including the visible violet have been attenuated equally.

Such white diffusers have the additional feature of reducing spectral reflections and glare. They were employed on GIA microscope lights (Figure 10) for this purpose and to filter UV. (Note that although they did a good job of reducing reflections and glare, they did not reduce the UV or the light intensity enough to avoid all grade whitening fluorescence.)

These observations are from past GIA course manuals and the measurements of UV of 9 uW and 600 fc light intensity at one inch grading distance from the microscope light with diffuser. The diffuser dropped the UV from over 150 uW to 9uW and the light intensity from 1000fc to 600fc. That was insufficient to avoid all grade whitening fluorescence from either the UV or the visible light. (Note that GIA's lighting specifications require light intensity to be between 200fc and 450fc ( 2000lux and 4500lux).

 

[michaelgem]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

This was a redundant unintended post.

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

To Garry's position, which Sharon seems to agree with, about substantial amounts of VV indoors ,I would like to more fully understand the impact of those wavelengths on N3 excitation and the degree of whitening possible in real world viewing environments.

I think it is pretty clear that UV indoors is not much of a factor at all, a point I think Garry has already acknowledged. And considering the info that Karl supplied about UV filtering of the film on office windows, and the measurements in dropoff in UV at short distances away from regular glass mentioned in the study, there is no significant UV present in the vast majority of indoor viewing environments. As Garry points out, that leaves the VV as a possible source of any whitening that might take place indoors.

Looking at the 3d Graph again in the Cowing study it appears that VV is a less powerful stimulator of fluorescence than the UV wavelengths.

So I am curious to know what minimum intensity (in footcandles) of visible light would be required to stimulate N3 centers enough to cause a color masking degree of fluorescence.

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Michael is this your opinion or a fact based on evidence and testing?

Michael: White diffusers like the one on the GIA microscope light reduce the visible light intensity by absorbing energy equally across all visible wavelengths including the visible violet. If it did not the quality/color of the light would change. (For example, if the VV and blue energy were attenuated more, the light quality would become yellowish, as happens in Cape Series type 1A diamonds.) The white plastic diffuser acts to lower light intensity similarly to a neutral density filter in photography, it absorbs/reduces all visible energy equally maintaining the color/quality/color temperature of the light.

This is all fact understood through spectrum analysis and colour science. The yellow tint in cape series type 1A diamonds is the result of the N3 center's greater attenuation of wavelengths in the violet and deep blue. When we observe that a filter like the one on the GIA microscope light does not change the light's quality/colour it is because all wavelengths including the visible violet have been attenuated equally.

Such white diffusers have the additional feature of reducing spectral reflections and glare. They were employed on GIA microscope lights (Figure 10) for this purpose and to filter UV. (Note that although they did a good job of reducing reflections and glare, they did not reduce the UV or the light intensity enough to avoid all grade whitening fluorescence.)

These observations are from past GIA course manuals and the measurements of UV of 9 uW and 600 fc light intensity at one inch grading distance from the microscope light with diffuser. The diffuser dropped the UV from over 150 uW to 9uW and the light intensity from 1000fc to 600fc. That was insufficient to avoid all grade whitening fluorescence from either the UV or the visible light. (Note that GIA's lighting specifications require light intensity to be between 200fc and 450fc ( 2000lux and 4500lux).

Since you did not answer my question Michael - the answer is you do not know for sure that the light coming from the microscope diffuser is balanced.
The fact it is in GIA course notes is not the basis of any evidence - because, as we both know, we can drive a truck through the gaps in many parts of GIA's course notes thru history.

Now actually I do not care, because color grading using a GIA microscope is not a GIA GTL practice, it is purely something taught to students at GIA courses, whcih again, have little to do with GIA GTL proprietary processes. What I care about is that you have a closed mind, and i am inviting you to test the theory that has a wide basis in behaviour - and that is that many many experianced diamond lovers like blur fluoro medium and strong diamonds. Why not find out why? Or prove thousands of people wrong.

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Could someone find a link to the survey on preferences for or against fluoro diamonds some consumers ran here about 5 to 10 years ago please?

Bump, please???

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

To Garry's position, which Sharon seems to agree with, about substantial amounts of VV indoors ,I would like to more fully understand the impact of those wavelengths on N3 excitation and the degree of whitening possible in real world viewing environments.

I think it is pretty clear that UV indoors is not much of a factor at all, a point I think Garry has already acknowledged. And considering the info that Karl supplied about UV filtering of the film on office windows, and the measurements in dropoff in UV at short distances away from regular glass mentioned in the study, there is no significant UV present in the vast majority of indoor viewing environments. As Garry points out, that leaves the VV as a possible source of any whitening that might take place indoors.

Looking at the 3d Graph again in the Cowing study it appears that VV is a less powerful stimulator of fluorescence than the UV wavelengths.

So I am curious to know what minimum intensity (in footcandles) of visible light would be required to stimulate N3 centers enough to cause a color masking degree of fluorescence.

Bryan the charts from GIA's 2013 artcile show a different result to those MC quoted from TH.
http://www.gia.edu/gems-gemology/summer-2013-luo-fluorescence-optical-defects

But again, what we observe is more important.
I am away and have no diamonds nor my camera to play with - but I wish people would start experimenting like David is.

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Michael is this your opinion or a fact based on evidence and testing?

Michael: White diffusers like the one on the GIA microscope light reduce the visible light intensity by absorbing energy equally across all visible wavelengths including the visible violet. If it did not the quality/color of the light would change. (For example, if the VV and blue energy were attenuated more, the light quality would become yellowish, as happens in Cape Series type 1A diamonds.) The white plastic diffuser acts to lower light intensity similarly to a neutral density filter in photography, it absorbs/reduces all visible energy equally maintaining the color/quality/color temperature of the light.

This is all fact understood through spectrum analysis and colour science. The yellow tint in cape series type 1A diamonds is the result of the N3 center's greater attenuation of wavelengths in the violet and deep blue. When we observe that a filter like the one on the GIA microscope light does not change the light's quality/colour it is because all wavelengths including the visible violet have been attenuated equally.

Such white diffusers have the additional feature of reducing spectral reflections and glare. They were employed on GIA microscope lights (Figure 10) for this purpose and to filter UV. (Note that although they did a good job of reducing reflections and glare, they did not reduce the UV or the light intensity enough to avoid all grade whitening fluorescence.)

These observations are from past GIA course manuals and the measurements of UV of 9 uW and 600 fc light intensity at one inch grading distance from the microscope light with diffuser. The diffuser dropped the UV from over 150 uW to 9uW and the light intensity from 1000fc to 600fc. That was insufficient to avoid all grade whitening fluorescence from either the UV or the visible light. (Note that GIA's lighting specifications require light intensity to be between 200fc and 450fc ( 2000lux and 4500lux).

Since you did not answer my question Michael - the answer is you do not know for sure that the light coming from the microscope diffuser is balanced.
The fact it is in GIA course notes is not the basis of any evidence - because, as we both know, we can drive a truck through the gaps in many parts of GIA's course notes thru history.

Now actually I do not care, because color grading using a GIA microscope is not a GIA GTL practice, it is purely something taught to students at GIA courses, whcih again, have little to do with GIA GTL proprietary processes. What I care about is that you have a closed mind, and i am inviting you to test the theory that has a wide basis in behaviour - and that is that many many experianced diamond lovers like blur fluoro medium and strong diamonds. Why not find out why? Or prove thousands of people wrong.

Garry,
I don't understand where your apparent hostility is coming from. Nobody here is suggesting that many people don't love fluoro stones. It seems to me Michael's article supports those very people by pointing out the need for more accurate color grading of this subset of diamonds, specifically to ensure consumers of fluoro stones are getting everything they bargain for, and so the best fluoro stones can be fully appreciated for their extra benefit.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

I can't speak for Garry- but I can say it's extremely frustrating to have this study, based on one grader's opinion on how much or little GIA or AGSL is misgrading stones being described as "science"
That's not a scientific study, it's Micheal's opinion.
Fine- we all have opinions. But that is NOT science.

Then we have Bryan's insistence that the whitening effect which is a physical reality isn't really happening.
It can't because of some light meter experiments done by Michael.

What's happening is clear. The meters are not picking up the spectrum that is causing the whitening. Personally, I don't need to know why it happens- but please carry on trying to figure it out

 

[michaelgem]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Michael is this your opinion or a fact based on evidence and testing?

Michael: White diffusers like the one on the GIA microscope light reduce the visible light intensity by absorbing energy equally across all visible wavelengths including the visible violet. If it did not the quality/color of the light would change. (For example, if the VV and blue energy were attenuated more, the light quality would become yellowish, as happens in Cape Series type 1A diamonds.) The white plastic diffuser acts to lower light intensity similarly to a neutral density filter in photography, it absorbs/reduces all visible energy equally maintaining the color/quality/color temperature of the light.

This is all fact understood through spectrum analysis and colour science. The yellow tint in cape series type 1A diamonds is the result of the N3 center's greater attenuation of wavelengths in the violet and deep blue. When we observe that a filter like the one on the GIA microscope light does not change the light's quality/colour it is because all wavelengths including the visible violet have been attenuated equally.

Such white diffusers have the additional feature of reducing spectral reflections and glare. They were employed on GIA microscope lights (Figure 10) for this purpose and to filter UV. (Note that although they did a good job of reducing reflections and glare, they did not reduce the UV or the light intensity enough to avoid all grade whitening fluorescence.)

These observations are from past GIA course manuals and the measurements of UV of 9 uW and 600 fc light intensity at one inch grading distance from the microscope light with diffuser. The diffuser dropped the UV from over 150 uW to 9uW and the light intensity from 1000fc to 600fc. That was insufficient to avoid all grade whitening fluorescence from either the UV or the visible light. (Note that GIA's lighting specifications require light intensity to be between 200fc and 450fc ( 2000lux and 4500lux).

Since you did not answer my question Michael - the answer is you do not know for sure that the light coming from the microscope diffuser is balanced.
The fact it is in GIA course notes is not the basis of any evidence - because, as we both know, we can drive a truck through the gaps in many parts of GIA's course notes thru history.

Not sure what part of the direct answer to your question is not understood and leading you to think it was not answered. When a filter like the one on the GIA microscope light attenuates and diffuses the light while not changing its quality/colour it is because all wavelengths including the visible violet have been attenuated equally. Any inequality in absorbtion results in a change in quality/colour.

The GIA microscope light was just one among seven lighting environments examined in this study. There were three examples examined of what you are referring to as GIA GTL proprietary, all of which represent the standard lighting prescribed by GIA in 2008. Analysis of the levels of UV and visible light intensity in relation to the grading obtained in these varying levels of UV and VV and those obtained in LED lighting and overhead fluorescent lighting is what has led to the conclusions drawn and the solutions recommended.

Now actually I do not care, because color grading using a GIA microscope is not a GIA GTL practice, it is purely something taught to students at GIA courses, whcih again, have little to do with GIA GTL proprietary processes. What I care about is that you have a closed mind, and i am inviting you to test the theory that has a wide basis in behaviour - and that is that many many experianced diamond lovers like blur fluoro medium and strong diamonds. Why not find out why? Or prove thousands of people wrong.

 

[michaelgem]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

I can't speak for Garry- but I can say it's extremely frustrating to have this study, based on one grader's opinion on how much or little GIA or AGSL is misgrading stones being described as "science"
That's not a scientific study, it's Micheal's opinion.
Fine- we all have opinions. But that is NOT science.

Then we have Bryan's insistence that the whitening effect which is a physical reality isn't really happening.
It can't because of some light meter experiments done by Michael.

What's happening is clear. The meters are not picking up the spectrum that is causing the whitening. Personally, I don't need to know why it happens- but please carry on trying to figure it out

Bryan understands that measurements of visible light intensity "pick up" (cover) the visible spectrum including the deep visible violet that is the part of the visible spectrum causing the whitening. He recognizes that by keeping that visible light intensity below 400fc keeps the VV at a level that did not cause grade whitening fluorescence. Most artificial lighting in the home and office at 3ft or greater is below 400fc and the UV below 1uW, which is why the true unenhanced color is seen.

There were three examples examined which represent the standard lighting prescribed by GIA in 2008. Analysis of the levels of UV and visible light intensity in relation to the grading obtained in these varying levels of UV and VV and those obtained in LED lighting and overhead fluorescent lighting is what has led to the conclusions drawn and the solutions recommended. Rather than opinion, the data obtained and analyzed is the actual grading by GIA GTL, and AGSL as well as me. As Bryan has pointed out, all three agree within tolerance on the grades of the study's 10 control diamonds with negligible fluorescence. The differences and inconsistancies arise and worsen as the strength of the diamond's fluorescence response goes from medium to strong to very strong blue.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Michael- I again appreciate your willingness to discus this.
When it comes to diamonds, I'm not a "science" guy in terms of practice- I have always been able to navigate the world of diamonds using rudimentary diamond grader tools, and my eyes.
Having said that, I have a lot of respect for people like you that dedicate a lot of time and thought to reasons why things happen.

Comparing GIA and AGSL grading is one thing.
If I was a writer of or a consultant on a paper claiming that GIA or AGSL is misgrading diamonds, I would insist that multiple graders confirm that inaccuracy.
This point renders the conclusions that you draw regarding overgrading to be unverified based on my grading experience.

My real life experiences, which include looking at countless GIA graded diamonds over the course of a year would indicate there is no problem- but that's really not the point. We can not use your grades to draw "scientific" conclusions about GIA's accuracy any more than mine.
When published in a trade journal the article has a different impact then when it's presented here in a consumer forum.
Hence my continued objections.
I'm sure if we have the chance to sit down over a beer we'll find a lot of common ground.

With regards to whitening effect- I suggest we use real life observations and extrapolate data. If the lighting is sufficient, whitening happens on some stones, of that I'm sure.

Experiment I just did.
Facing up actual diamonds.
I looked at an E color SB in my office lighting, at 220 lux- I can't notice the slight blue.
But then again, in that lighting, I can't really see the difference between it, another E with no blue and an H no blue.
Directly under the grading lamp, at about 2500 lux, I can definitely see the difference in color between the E's and the H. The grading lamp is not "activating" the fluorescence under these conditions.
I know for a fact the SB looks a bit blue when viewed under the same grading lamp, during a sunny day.
I generally am not looking at stones under dark field illumination- and I suspect most consumers also look at their diamonds in rooms with windows.
When there's a lot of light, it's going to contain whatever you may need to activate the whitening.

 

[michaelgem]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

To Garry's position, which Sharon seems to agree with, about substantial amounts of VV indoors ,I would like to more fully understand the impact of those wavelengths on N3 excitation and the degree of whitening possible in real world viewing environments.

I think it is pretty clear that UV indoors is not much of a factor at all, a point I think Garry has already acknowledged. And considering the info that Karl supplied about UV filtering of the film on office windows, and the measurements in dropoff in UV at short distances away from regular glass mentioned in the study, there is no significant UV present in the vast majority of indoor viewing environments. As Garry points out, that leaves the VV as a possible source of any whitening that might take place indoors.

Looking at the 3d Graph again in the Cowing study it appears that VV is a less powerful stimulator of fluorescence than the UV wavelengths.

So I am curious to know what minimum intensity (in footcandles) of visible light would be required to stimulate N3 centers enough to cause a color masking degree of fluorescence.

Bryan,

Because they contain negligible UV, The Dazor - Lumiled swing arm desklamp, Source 6 in the study, along with the overhead lighting, Source 7, provide bounds on the minimum light intensity that can cause grade whitening fluorescence. The Source 7, over head light intensity of 200fc stimulated no grade whitening amounts of fluorescence in even the five VST Blues. The Source 6 LED lighting when its intensity was turned down to 200fc also stimulated no blue fluorescence. So 200fc is the lower bound at or below which no fluorescence is stimulated. In the LED lighting at its full intensity of 600fc, half of the VST and ST Blues graded higher, but only by one grade. So the upper bound, where no grade whitening fluorescence occurs, is somewhat below 600fc for LED lighting, but even at 600fc the little visible violet that is present stimulates almost no grade whitening.

It is a different story for fluorescent lighting with its 405nm mercury vapor peak in the VV. More grade whitening is observed at 600fc in the UV filtered fluorescent lighting of the Source 1 DiamondLite and the Source 5, GIA Microscope Lamp. These two fluorescent light sources at the same 600fc intensity with their UV filtered out were in close agreement finding an average 1.5 grades of enhancement over the ten VST and ST Blue diamonds. Without UV to blame, this whitening is attributed to fluorescence excitation by the 405nm mercury peak in the Visible Violet. To avoid this grade enhancement the fluorescent light intensity must be considerably lower than 600fc leading to the recommendation to keep it below 400fc. GIA's DiamondDock standard lighting is an intensity of between 200 and 450fc which may be low enough to avoid grade whitening from VV in all but the most highly fluorescent diamonds.

From the study's data we can conclude that in fluorescent lighting the minimum intensity of visible light that can stimulate N3 centers enough to cause a color masking degree of fluorescence is between 200fc and 600fc, likely about 400fc. In LED lighting the minimum intensity is between 400fc and 600fc, likely about 500fc.

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

To Garry's position, which Sharon seems to agree with, about substantial amounts of VV indoors ,I would like to more fully understand the impact of those wavelengths on N3 excitation and the degree of whitening possible in real world viewing environments.

I think it is pretty clear that UV indoors is not much of a factor at all, a point I think Garry has already acknowledged. And considering the info that Karl supplied about UV filtering of the film on office windows, and the measurements in dropoff in UV at short distances away from regular glass mentioned in the study, there is no significant UV present in the vast majority of indoor viewing environments. As Garry points out, that leaves the VV as a possible source of any whitening that might take place indoors.

Looking at the 3d Graph again in the Cowing study it appears that VV is a less powerful stimulator of fluorescence than the UV wavelengths.

So I am curious to know what minimum intensity (in footcandles) of visible light would be required to stimulate N3 centers enough to cause a color masking degree of fluorescence.

Bryan,

Because they contain negligible UV, The Dazor - Lumiled swing arm desklamp, Source 6 in the study, along with the overhead lighting, Source 7, provide bounds on the minimum light intensity that can cause grade whitening fluorescence. The Source 7, over head light intensity of 200fc stimulated no grade whitening amounts of fluorescence in even the five VST Blues. The Source 6 LED lighting when its intensity was turned down to 200fc also stimulated no blue fluorescence. So 200fc is the lower bound at or below which no fluorescence is stimulated. In the LED lighting at its full intensity of 600fc, half of the VST and ST Blues graded higher, but only by one grade. So the upper bound, where no grade whitening fluorescence occurs, is somewhat below 600fc for LED lighting, but even at 600fc the little visible violet that is present stimulates almost no grade whitening.

. In LED lighting the minimum intensity is between 400fc and 600fc, likely about 500fc.[

Michael, Do you have any suggestions as to why LED lighting, which is usually totally devoid of VV, can cause grade whitening when the level of light is higher? Thomas says, and the charts I have seen of the spectra of LED's have nothing from 415nm down.

 

[michaelgem]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

To Garry's position, which Sharon seems to agree with, about substantial amounts of VV indoors ,I would like to more fully understand the impact of those wavelengths on N3 excitation and the degree of whitening possible in real world viewing environments.

I think it is pretty clear that UV indoors is not much of a factor at all, a point I think Garry has already acknowledged. And considering the info that Karl supplied about UV filtering of the film on office windows, and the measurements in dropoff in UV at short distances away from regular glass mentioned in the study, there is no significant UV present in the vast majority of indoor viewing environments. As Garry points out, that leaves the VV as a possible source of any whitening that might take place indoors.

Looking at the 3d Graph again in the Cowing study it appears that VV is a less powerful stimulator of fluorescence than the UV wavelengths.

So I am curious to know what minimum intensity (in footcandles) of visible light would be required to stimulate N3 centers enough to cause a color masking degree of fluorescence.

Bryan,

Because they contain negligible UV, The Dazor - Lumiled swing arm desklamp, Source 6 in the study, along with the overhead lighting, Source 7, provide bounds on the minimum light intensity that can cause grade whitening fluorescence. The Source 7, over head light intensity of 200fc stimulated no grade whitening amounts of fluorescence in even the five VST Blues. The Source 6 LED lighting when its intensity was turned down to 200fc also stimulated no blue fluorescence. So 200fc is the lower bound at or below which no fluorescence is stimulated. In the LED lighting at its full intensity of 600fc, half of the VST and ST Blues graded higher, but only by one grade. So the upper bound, where no grade whitening fluorescence occurs, is somewhat below 600fc for LED lighting, but even at 600fc the little visible violet that is present stimulates almost no grade whitening.

. In LED lighting the minimum intensity is between 400fc and 600fc, likely about 500fc.[

Michael, Do you have any suggestions as to why LED lighting, which is usually totally devoid of VV, can cause grade whitening when the level of light is higher? Thomas says, and the charts I have seen of the spectra of LED's have nothing from 415nm down.

Good question, Garry,

Here, from Dazor are curves of fluorescent lighting, quartz halogen lighting and LED lighting. If there is any energy in LED light at or below 415.2nm it isn't much. It doesn't seem enough to account for any grade whitening.



I commented previously: " In the LED lighting at its full intensity of 600fc, half of the VST and ST Blues graded higher, but only by one grade. So the upper bound, where no grade whitening fluorescence occurs, is somewhat below 600fc for LED lighting, but even at 600fc the little visible violet that is present stimulates almost no grade whitening."

It is likely that observed average half-grade of whitening will have to be chalked up to grading variability.
In any event, keeping all grading light below 400fc should ensure no grade whitening from the visible violet unless the fluorescence response is extremely strong.

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Michael, Do you have any suggestions as to why LED lighting, which is usually totally devoid of VV, can cause grade whitening when the level of light is higher? Thomas says, and the charts I have seen of the spectra of LED's have nothing from 415nm down.


Good question, Garry,

Here, from Dazor are curves of fluorescent lighting, quartz halogen lighting and LED lighting. If there is any energy in LED light at or below 415.2nm it isn't much. It doesn't seem enough to account for any grade whitening.

Image

I commented previously: " In the LED lighting at its full intensity of 600fc, half of the VST and ST Blues graded higher, but only by one grade. So the upper bound, where no grade whitening fluorescence occurs, is somewhat below 600fc for LED lighting, but even at 600fc the little visible violet that is present stimulates almost no grade whitening."

It is likely that observed average half-grade of whitening will have to be chalked up to grading variability.
In any event, keeping all grading light below 400fc should ensure no grade whitening from the visible violet unless the fluorescence response is extremely strong.

I think there might be more to it Michael.
I would like to add a new dimension to the discussion.
From Wikipedia human eye sensitivity is skewed toward green and with a bit more emphasis on the orange/ red than blue /violet.
There is, it appears to be more to this than simply the science of the material itself.

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Oh No! Not neuroscience too. Please

I would like to add a new dimension to the discussion.
From Wikipedia human eye sensitivity is skewed toward green and with a bit more emphasis on the orange/ red than blue /violet.
There is, it appears to be more to this than simply the science of the material itself.

Garry,
Can you elaborate on how the color sensitivity might play a role in the observations? I don't think I am understanding your point. If sensitivity is skewed towards the warmer side of the spectrum, would that not tend to make the effects of blue fluorescence even more difficult to discern in real life?

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

To Garry's position, which Sharon seems to agree with, about substantial amounts of VV indoors ,I would like to more fully understand the impact of those wavelengths on N3 excitation and the degree of whitening possible in real world viewing environments.

I think it is pretty clear that UV indoors is not much of a factor at all, a point I think Garry has already acknowledged. And considering the info that Karl supplied about UV filtering of the film on office windows, and the measurements in dropoff in UV at short distances away from regular glass mentioned in the study, there is no significant UV present in the vast majority of indoor viewing environments. As Garry points out, that leaves the VV as a possible source of any whitening that might take place indoors.

Looking at the 3d Graph again in the Cowing study it appears that VV is a less powerful stimulator of fluorescence than the UV wavelengths.

So I am curious to know what minimum intensity (in footcandles) of visible light would be required to stimulate N3 centers enough to cause a color masking degree of fluorescence.

Bryan,

Because they contain negligible UV, The Dazor - Lumiled swing arm desklamp, Source 6 in the study, along with the overhead lighting, Source 7, provide bounds on the minimum light intensity that can cause grade whitening fluorescence. The Source 7, over head light intensity of 200fc stimulated no grade whitening amounts of fluorescence in even the five VST Blues. The Source 6 LED lighting when its intensity was turned down to 200fc also stimulated no blue fluorescence. So 200fc is the lower bound at or below which no fluorescence is stimulated. In the LED lighting at its full intensity of 600fc, half of the VST and ST Blues graded higher, but only by one grade. So the upper bound, where no grade whitening fluorescence occurs, is somewhat below 600fc for LED lighting, but even at 600fc the little visible violet that is present stimulates almost no grade whitening.

It is a different story for fluorescent lighting with its 405nm mercury vapor peak in the VV. More grade whitening is observed at 600fc in the UV filtered fluorescent lighting of the Source 1 DiamondLite and the Source 5, GIA Microscope Lamp. These two fluorescent light sources at the same 600fc intensity with their UV filtered out were in close agreement finding an average 1.5 grades of enhancement over the ten VST and ST Blue diamonds. Without UV to blame, this whitening is attributed to fluorescence excitation by the 405nm mercury peak in the Visible Violet. To avoid this grade enhancement the fluorescent light intensity must be considerably lower than 600fc leading to the recommendation to keep it below 400fc. GIA's DiamondDock standard lighting is an intensity of between 200 and 450fc which may be low enough to avoid grade whitening from VV in all but the most highly fluorescent diamonds.

From the study's data we can conclude that in fluorescent lighting the minimum intensity of visible light that can stimulate N3 centers enough to cause a color masking degree of fluorescence is between 200fc and 600fc, likely about 400fc. In LED lighting the minimum intensity is between 400fc and 600fc, likely about 500fc.

That seems to be a logical conclusion based upon the observations in your study. I guess I am looking for some sort of direct measurement as a way to corroborate that conclusion. I think it would be very interesting to see a 3D excitation graph done at decending levels of light intensity. E.g 1000fc, 600fc, 400fc, 200fc, 100fc.

I think someone posted something like this earlier but here is another list of typical light intensities in a variety of real world lighting scenarios (in footcandles):

Full moon on a clear night 0.025
Night time in town 0.35
Living room at home 5
Hallway 8
Very overcast day 10
Office 30-50
Sunrise on a clear day 40
Typical TV studio lighting 100
Full daylight but not direct sunlight 1,000-2,500
Direct sunlight 3,000->10,000

Similar information can be found here : http://sustainabilityworkshop.autodesk.com/buildings/measuring-light-levels

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

How do lux and footcandles relate?
I have a light meter that reads in lux- is there a conversion to footcandles?

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

How do lux and footcandles relate?
I have a light meter that reads in lux- is there a conversion to footcandles?

Lux to footcandles conversion formula
The illuminance Ev in lux (lx) is equal to the illuminance Ev in footcandles (fc) divided by 0.09290304:
Ev(lx) = Ev(fc) / 0.09290304 = Ev(fc) × 10.76391

If you divide your lux reading by 10 it will give you a close approximation. Since the reading on your lux meter is stopped down by 10x, the actual readout on your meter is close to the value in footcandles.

 

[Modified Brilliant]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

I can't add anything to this discussion because...I'm LOST!

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

I can't add anything to this discussion because...I'm LOST!

Come on Jeff. You can do it. Re-read all 8 pages of the thread over the weekend and get back to us.

We are closing in on the holy grail here and we need all the help we can get.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

I can't add anything to this discussion because...I'm LOST!

Hi Jeff- you can definitely add!
A few key points of debate in this discussion
1) Is there a problem which negatively affect consumers due to GIA issuing incorrect grades on Fluoro diamonds?
2) Are there fluoro stones that show a whitening in lighting which is bright enough to distinguish color? This as opposed to only improving when they are held close to a grading lamp ( which we pretty much all agree on)

As a valued member/professional your experience is indeed of value.

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Oh No! Not neuroscience too. Please

I would like to add a new dimension to the discussion.
From Wikipedia human eye sensitivity is skewed toward green and with a bit more emphasis on the orange/ red than blue /violet.
There is, it appears to be more to this than simply the science of the material itself.

Garry,
Can you elaborate on how the color sensitivity might play a role in the observations? I don't think I am understanding your point. If sensitivity is skewed towards the warmer side of the spectrum, would that not tend to make the effects of blue fluorescence even more difficult to discern in real life?

Are 3/4's of PS consumers wrong to like fluoro diamonds?
The very same consumers who are incredibly picky about cut and every diamond aspect.
People who by and large really know how to look at diamonds?

Are all the people who report grade whitening (including me and many of my staff and clients) wrong?

If we are right, and there is a reason for it, it would be great to find it. And I propose that the science is more complex than what Michael looked at - there seems to be more to it. I don't have the answer or answers.

But Bryan, please do something for me - get some H's or I's of the same size in non and strong blue and look at them it different places.

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Oh No! Not neuroscience too. Please

I would like to add a new dimension to the discussion.
From Wikipedia human eye sensitivity is skewed toward green and with a bit more emphasis on the orange/ red than blue /violet.
There is, it appears to be more to this than simply the science of the material itself.

Garry,
Can you elaborate on how the color sensitivity might play a role in the observations? I don't think I am understanding your point. If sensitivity is skewed towards the warmer side of the spectrum, would that not tend to make the effects of blue fluorescence even more difficult to discern in real life?

Are 3/4's of PS consumers wrong to like fluoro diamonds?
The very same consumers who are incredibly picky about cut and every diamond aspect.
People who by and large really know how to look at diamonds?

Are all the people who report grade whitening (including me and many of my staff and clients) wrong?

If we are right, and there is a reason for it, it would be great to find it. And I propose that the science is more complex than what Michael looked at - there seems to be more to it. I don't have the answer or answers.

But Bryan, please do something for me - get some H's or I's of the same size in non and strong blue and look at them it different places.

Garry,
The poll is interesting and particularly informative because responders were asked to specify WHY they liked fluorescence in diamonds. I have not yet had time to go through the entire thread, but the first couple of pages indicate to me that a large number of the votes in favor of fluorescence had to do with the blue glow in sunlight, the discounted price, the cool look under black lights, etc - things that nobody here is questioning. Relatively few (at least in the first few pages) pointed to a whitening effect under normal conditions.

[URL='https://www.pricescope.com/community/threads/fluorescence-poll-do-you-like-it-yes-or-no-and-why.84923/']https://www.pricescope.com/community/threads/fluorescence-poll-do-you-like-it-yes-or-no-and-why.84923/[/URL]

 

[Karl_K]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

. In LED lighting the minimum intensity is between 400fc and 600fc, likely about 500fc.[/color][

Michael, Do you have any suggestions as to why LED lighting, which is usually totally devoid of VV, can cause grade whitening when the level of light is higher? Thomas says, and the charts I have seen of the spectra of LED's have nothing from 415nm down.

The spectrum of led lighting varies greatly with how they are driven and cooled.
They are driven by a constant current supply if you want any kind of controllable lighting and turned off and on quickly the duty cycle(ratio of how long they are off to on) determines the lighting level as the brain/eyes averages it.
Voltage is not as critical as current as long as you don't exceed a damaging voltage level.
Temperature can also be controlled by controlling the current and heat sink effectiveness.
It is possible that the leds used throw off wavelengths that will excite diamonds when hot or if driven to hard.
That is one reason higher light levels may change things.

Picking leds for a scientific instrument is very challenging and consistent supply and testing can be problematic.
Driving them is also very challenging.
Like anything else there will be compromises that will have to be made.
Control of the led specifications and how they are driven is the difference between a harbor fright $3 led light and a $150 scientific grade led light source.

 

[michaelgem]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

To Garry's position, which Sharon seems to agree with, about substantial amounts of VV indoors ,I would like to more fully understand the impact of those wavelengths on N3 excitation and the degree of whitening possible in real world viewing environments.

I think it is pretty clear that UV indoors is not much of a factor at all, a point I think Garry has already acknowledged. And considering the info that Karl supplied about UV filtering of the film on office windows, and the measurements in dropoff in UV at short distances away from regular glass mentioned in the study, there is no significant UV present in the vast majority of indoor viewing environments. As Garry points out, that leaves the VV as a possible source of any whitening that might take place indoors.

Looking at the 3d Graph again in the Cowing study it appears that VV is a less powerful stimulator of fluorescence than the UV wavelengths.

So I am curious to know what minimum intensity (in footcandles) of visible light would be required to stimulate N3 centers enough to cause a color masking degree of fluorescence.

Bryan,

Because they contain negligible UV, The Dazor - Lumiled swing arm desklamp, Source 6 in the study, along with the overhead lighting, Source 7, provide bounds on the minimum light intensity that can cause grade whitening fluorescence. The Source 7, over head light intensity of 200fc stimulated no grade whitening amounts of fluorescence in even the five VST Blues. The Source 6 LED lighting when its intensity was turned down to 200fc also stimulated no blue fluorescence. So 200fc is the lower bound at or below which no fluorescence is stimulated. In the LED lighting at its full intensity of 600fc, half of the VST and ST Blues graded higher, but only by one grade. So the upper bound, where no grade whitening fluorescence occurs, is somewhat below 600fc for LED lighting, but even at 600fc the little visible violet that is present stimulates almost no grade whitening.

. In LED lighting the minimum intensity is between 400fc and 600fc, likely about 500fc.[

Michael, Do you have any suggestions as to why LED lighting, which is usually totally devoid of VV, can cause grade whitening when the level of light is higher? Thomas says, and the charts I have seen of the spectra of LED's have nothing from 415nm down.

Good question, Garry,

Here, from Dazor are curves of fluorescent lighting, quartz halogen lighting and LED lighting. If there is any energy in LED light at or below 415.2nm it isn't much. It doesn't seem enough to account for any grade whitening.



I commented previously: " In the LED lighting at its full intensity of 600fc, half of the VST and ST Blues graded higher, but only by one grade. So the upper bound, where no grade whitening fluorescence occurs, is somewhat below 600fc for LED lighting, but even at 600fc the little visible violet that is present stimulates almost no grade whitening."

It is likely that observed average half-grade of whitening will have to be chalked up to grading variability.
In any event, keeping all grading light below 400fc should ensure no grade whitening from the visible violet unless the fluorescence response is extremely strong.

Karl writes:
The spectrum of led lighting varies greatly with how they are driven and cooled.
They are driven by a constant current supply if you want any kind of controllable lighting and turned off and on quickly the duty cycle(ratio of how long they are off to on) determines the lighting level as the brain/eyes averages it.

Voltage is not as critical as current as long as you don't exceed a damaging voltage level.
Temperature can also be controlled by controlling the current and heat sink effectiveness.
It is possible that the leds used throw off wavelengths that will excite diamonds when hot or if driven to hard.
That is one reason higher light levels may change things.

Picking leds for a scientific instrument is very challenging and consistent supply and testing can be problematic.
Driving them is also very challenging.
Like anything else there will be compromises that will have to be made.
Control of the led specifications and how they are driven is the difference between a harbor fright $3 led light and a $150 scientific grade led light source.

Thanks, Karl for this input about LED lighting.

It may well be why I saw some small whitening from the Dazor LumiLeds run at full power of 600fc. It may explain why, in the LED lighting at its full intensity of 600fc, half of the VST and ST Blues graded higher by one grade. It is likely safe to say that dialing back to 400fc assures no whitening from any small amount of visible violet possible in LED lighting.

 

[Karl_K]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

It may well be why I saw some small whitening from the Dazor LumiLeds run at full power of 600fc. It may explain why, in the LED lighting at its full intensity of 600fc, half of the VST and ST Blues graded higher by one grade. It is likely safe to say that dialing back to 400fc assures no whitening from any small amount of visible violet possible in LED lighting.

only with those specific leds driven in that specific manner.
Choosing other leds and driving them different could result with a 1000fc light level with no whitening wavelenths, on the other hand you could get them with 100fc with others or even the same ones driven differently.
Controlling your variables is what makes this type of study so hard to do and if you don't how can someone repeat it to verify your results?

 

[sharonp]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

I can't speak for Garry- but I can say it's extremely frustrating to have this study, based on one grader's opinion on how much or little GIA or AGSL is misgrading stones being described as "science"

What I find frustrating is that you have trouble reading and retaining what you read, above you asked for the conversion of foot candles to lux I already posted that in quote to you a few pages back https://www.pricescope.com/communit...revisited.219341/page-6#post-4005239#p4005239
, and clearly you have no experience reading scientific literature, yet you have self appointed yourself qualified as an editor to dismiss the article.

It is science, the methodlogy is sound, and the following conclusions are valid even if the results aren't as robust or variable controlled as many would like:

Looking at a scatter plot of VSB and SB diamonds within a limited dataset there is a clear indication of grade whitening. With SB its almost 2 grades with VSB even more. The trend is pretty clear and is what is important not the individual grades.

That doesn't mean every VSB or SB would be graded 2 grades lower by GIA-GTL if they used a lexan filter and diffuser but it means that it is likely that some or possibly all diamonds would be graded lower by 0 - 4 grades.

Now to strengthen this paper it would be best to get permission from AGSL to install a Lexan Filter and diffuser into their grading box to keep all variables the same and have their actual graders regrade the stones.

They may object to doing that, but in the interest of education hopefully they might agree.

Even then I expect you will then say AGSL is not equivalent to GIAL and Garry will find something else to complain about like machine grading(which is certainly not reccomended by GIA-GTL for Fluro stones) and you two will never be satisfied.

 

[sharonp]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

HI Sharon,
The article does spell out a lot of details, it's true. I had not read it. I based my statements on GIA not discussing specific methods because I have spoken to GIA personnel about this in the past.

I did notice this from page 307. This backs up what I've been saying about a single color grader.
To control for potential perception differences
from individual to individual, GIA’s grading process
requires a minimum of two or three random, independent
opinions (depending on the size of the
stone). A consensus is required before a color grade is
finalized. For larger or potentially D-color stones, the
laboratory’s computer operating system identifies
the need for the most experienced graders. Last, to
avoid the potential of reduced accuracy due to eye
fatigue, color grading sessions are limited to approximately
one hour, at which point a minimum break
of one hour must be taken.

Michael is not issuing a grading report for these diamonds his conclusions are about a trend in color grading data. Unless you can prove the trend is systematically biased towards unwarranted lower grades, or that his grading error is 2 grades or more they still stand. I wouldn't say from the data I could prove any whitening for MB or Faint, but from SB and VSB the trend seems pretty strong.

With regards to Rappaport pricing studies.
I believe what I did a few pages back with 1.00-1.05 D-E-F VS1 XXX RBC gives us a general idea that discounts have increased since 1998. I personally have found that to be true.

What you did a few pages back is not detailed or accurate enough, the discounts are nothing close to 20% across the color grading spectrum. Some Near Colorless Diamonds actually trade for more with Fluoro not less. You are not willing to put in the time to provide any data to this discussion but this thread is certainly full of your opinionated rhetoric and farcical 'Experiments'

 

[Rockdiamond]

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.

There's just no other "proof" Michael's claims have any validity.
Besides other graders agreeing that GIA is doing this wrong, that proof would be other trade members, or consumers complaining that a problem exists.

True I'm not trained in reading scientific journals- but you'll be hard pressed to find anyone with equal or greater experience in diamond grading and dealing with both GIA as well as consumers. I can read the conclusions, and they are the issue here.