Fluorescence-AGS question

[gemcat]

Does anyone know how fluorescence is graded in the AGS lab? I know it has to be under UV light, but is it done in a hood of some type? Under normal room lighting? In a darkened room?
The reason I ask, is I have a diamond AGS certified as "Negligible" fluorescence. When I look at it under the UV light on my loupe, in a darkened room, it practically glows blue. I'm not sure how to reconcile the strong blue glow I see with the term "Negligible". Any education from you experts would be appreciated.

 

[LaylaR]

Negligible at AGS means anywhere from none to just under medium which is their next highest designation.

 

[Stephan]

You are not the first one to mention this:
https://www.pricescope.com/community/threads/so-about-that-negligible-flouresence.244370/
As all the super ideal cut diamonds sellers have all the tools to provide ASET, H&A pictures, etc., I would love them to use GIA instead of AGS.
I think fluorescence is only a good thing for fluorescence lovers, personally I think it never adds value to a diamond.

 

[Texas Leaguer]

Does anyone know how fluorescence is graded in the AGS lab? I know it has to be under UV light, but is it done in a hood of some type? Under normal room lighting? In a darkened room?
The reason I ask, is I have a diamond AGS certified as "Negligible" fluorescence. When I look at it under the UV light on my loupe, in a darkened room, it practically glows blue. I'm not sure how to reconcile the strong blue glow I see with the term "Negligible". Any education from you experts would be appreciated.

AGS takes a slightly different approach to reporting on fluorescence than GIA. There is a section in this AGSL color grading article that touches on it.
https://www.pricescope.com/articles/ags-laboratory-color-grading-diamonds

One of the issues that creates some concern and confusion in the consumer market is the myriad of different UV light sources in use today, both among professionals and in the consumer realm. Depending on the particular instrument, the fluorescent reaction of a given diamond can vary significantly.

 

[EvaEvans]

AGS is not reliable about fluorescence. I would not trust them in this regard.

 

[Texas Leaguer]

AGS is not reliable about fluorescence. I would not trust them in this regard.

Not reliable in what sense?

 

[Diamond_Hawk]

AGS is not reliable about fluorescence. I would not trust them in this regard.

Can you clarify?

 

[WinkHPD]

I would love them to use GIA instead of AGS.

When, and if, GIA ever develops a good cut grade metric instead of the sell out, make the manufacturers happy system that it has now, maybe some of the better cutters will consider using GIA for cut grade on their best cut stones. In the mean time, GIA has a cut grade system that calls both excellent and mediocre cut stones Excellent. This is great for the manufacturers, but horrible for the consumer who does not know how to tell which Excellents are, and which Excellents are not.

Wink

 

[Garry H (Cut Nut)]

Does anyone know how fluorescence is graded in the AGS lab? I know it has to be under UV light, but is it done in a hood of some type? Under normal room lighting? In a darkened room?
The reason I ask, is I have a diamond AGS certified as "Negligible" fluorescence. When I look at it under the UV light on my loupe, in a darkened room, it practically glows blue. I'm not sure how to reconcile the strong blue glow I see with the term "Negligible". Any education from you experts would be appreciated.

AGS (and GIA) use an ancient 365nm frequency used for gemstone ID. Wrong. Bad. GIA have patents mentioning a more correct near visible UV which is more like the cheap UV LED's you probably used.
When GIA change I am sure AGS will too.
And when the entire world wakes up, you will wish you bought a diamond with Strong Blue fluoro.

 

[TreeScientist]

You are not the first one to mention this:
https://www.pricescope.com/community/threads/so-about-that-negligible-flouresence.244370/
As all the super ideal cut diamonds sellers have all the tools to provide ASET, H&A pictures, etc., I would love them to use GIA instead of AGS.
I think fluorescence is only a good thing for fluorescence lovers, personally I think it never adds value to a diamond.

JannPaul Diamonds is a SuperIdeal vendor that carries primarily GIA-certified diamonds, and also provides all of the reflector images. They're in Singapore though, so may or may not work for you depending on your geographical location.

It is quite disappointing to see so many reports of AGS Neg stones exhibiting obvious fluorescence. Part of this is obviously because they grouped none and faint together into one designation, but it is also due to the use of a single UV frequency by BOTH GIA and AGS for fluorescence grading. A stone that doesn't fluoresce under 365nm may fluoresce under a different wavelength. It would be nice if the labs graded under two different lamps, one shortwave UV and one longwave UV, before assigning a negligible or none designation to a diamond, but as they say, old habits die hard...

As a consumer, it is fairly easy to test this yourself though. Seeing as pretty much every online vendor has a 30-day return policy, just buy a $10 blacklight to test any diamond you order. If it fluoresces more than you like under the cheap blacklight or under sunlight, then send it back.

 

[EvaEvans]

Not reliable in what sense?

I have seen AGS certified diamonds with "negligible" fluorescence to glow as a Christmas tree...
Not faint, at least medium blue fluorescence described as "negligible"?! I call this "NOT reliable" in regard to measuring fluorescence.
In my practice GIA never fail to described the correct fluorescence level.

 

[EvaEvans]

GIA have patents mentioning a more correct near visible UV which is more like the cheap UV LED's you probably used.

Yes, GIA uses the so called "long wave UV light" (the cheap UV flashlight). Why? Because the long UV wave length is natural part of the daylight and can impact the human eyes perception.
Here is the GIA explanation:
"On a GIA Diamond Grading Report, fluorescence refers to the strength, or intensity, of the diamond’s reaction to long-wave UV, which is an essential component of daylight."

 

[TreeScientist]

Yes, GIA uses the so called "long wave UV light" (the cheap UV flashlight). Why? Because the long UV wave length is natural part of the daylight and can impact the human eyes perception.
Here is the GIA explanation:
"On a GIA Diamond Grading Report, fluorescence refers to the strength, or intensity, of the diamond’s reaction to long-wave UV, which is an essential component of daylight."

Both labs currently use longwave UV. 365nm is longwave. GIA is not different from AGS in that regard (although I agree that GIA is more accurate at fluorescence grading, in that a GIA "none" usually does not fluoresce to any appreciable degree).

But the sun does not produce UV light at a single wavelength. Sunlight reaching the Earth's surface contains significant amounts of UV light from about 310nm all the way to 379nm (the beginning of the visible spectrum). It would be nice if the labs used a "broad spectrum" UV lamp for grading, with wavelengths spanning the range of surface-level sunlight, seeing as sunlight likely comprises 99% of the UV light your diamond will be exposed to unless you happen to frequent nightclubs or raves .

 

[EvaEvans]

@TreeScientist
What is important when measuring fluorescence is how it can impact the human's eye perception. So as longer UV light wave is measured (UV close to the visible light), as better.
GIA is much more accurate in measuring fluorescence. In fact, I haven't experienced GIA flaw regarding fluorescence.

 

[Johnbt]

"When I look at it under the UV light"

I'm curious about the brand or make of light you are using. I've considered buying an inexpensive UV light and there are so many kinds available with a wide variety of specifications (or no listed specs.) Some of the cheapest ones I've examined at the hardware store seem to throw a great deal of blue/violet light.

 

[Texas Leaguer]

Fluorescence reporting was originally intended as an identifying characteristic- not a performance characteristic- and that is still the primary purpose. It therefore makes logical sense for the labs to use 365 to make that assessment.

Here is one of the most up to date studies on the topic:
https://www.gia.edu/gems-gemology/summer-2013-luo-fluorescence-optical-defects

Especially interesting is the detailed testing of various devices used by trade members and consumers and the variable results they produce, prompting the following comments by the authors:

“The variability in excitation wavelengths and bandwidths among commonly used lamps and LED UV sources demonstrates that the colors and intensities of observed fluorescence in a single sample can vary depending on the light source.”

"Traditional gemological UV lamps and light sources used in the diamond industry produce widely variable emissions, making it difficult to achieve reproducible fluorescence observations."

“…small changes in excitation wavelength, even from a “pure” LWUV emission, can significantly affect the intensity and possibly the color of the fluorescence.”

“LED sources are far more constrained in emission bandwidth and purity, but they are manufactured in such a wide range of wavelengths that consistency among different products remains a problem.”

 

[Paul-Antwerp]

@TreeScientist
What is important when measuring fluorescence is how it can impact the human's eye perception. So as longer UV light wave is measured (UV close to the visible light), as better.
GIA is much more accurate in measuring fluorescence. In fact, I haven't experienced GIA flaw regarding fluorescence.

Eva, I do not know your exposure to diamonds, but please allow me to clarify what we perceive with regards to the grading of fluorescence.

Our team literally sees hundreds of GIA-graded diamonds each and every week, and as far as the grading of GIA goes, we regard their grading of fluorescence as by far the least reliable. Most of GIA-graded Faint, we regard as Medium, regularly Strong. And a reasonable number of GIA-graded None, we internally consider Faint, sometimes Medium. Our further perception is that this level of GIA being off on the fluorescence-grade is mostly an event of the last two years. Before that, we considered them acceptable in this grade. That has unfortunately changed, and it has a side-effect on the wholesale-market. Before 2016, there was hardly a discount for a GIA-Faint compared to a GIA-None. Nowadays, it is clear that wholesalers have to sell GIA-Faint with a discount.

As far as fluorescence-grading of AGS goes, I must state that our experience is colored, as our experience with AGS is limited to us sending our own production there. Now, in production, we wish to avoid receiving an accidental Medium-grade since a few years and we thus use a 'safe' internal fluo-grade to make sure that we are in the high end of Negligible. As such, I cannot comment on how far 'down' the Negligible-grade of AGS goes, as we are not 'testing' that boundary.

In summary, our team from experience does not trust the current GIA-grade of fluorescence. We cannot really comment if the AGS-grading is better or worse, simply because of lack of experience.

In this thread, however, I found Garry's post very interesting and worthy of a further discussion. Since this thread already went in a totally different direction, I suggest starting up a new thread regarding Garry's topic.

Live long,

 

[EvaEvans]

@Paul-Antwerp
I would agree with one of your statement - everybody speaks based of his own experience!
All my 15sh GIA - USA - New York graded diamonds I can say have absolutely accurate grade of fluorescence. As GIA is international lab, and my own diamonds are very limited number, I cannot judge in general, then.
After purchasing few AGS diamonds I realized I cannot trust this lab in regard of fluorescence.
Everybody is free to have his own opinion, based on his own experience.

 

[Garry H (Cut Nut)]

Eva, I do not know your exposure to diamonds, but please allow me to clarify what we perceive with regards to the grading of fluorescence.

Our team literally sees hundreds of GIA-graded diamonds each and every week, and as far as the grading of GIA goes, we regard their grading of fluorescence as by far the least reliable. Most of GIA-graded Faint, we regard as Medium, regularly Strong. And a reasonable number of GIA-graded None, we internally consider Faint, sometimes Medium. Our further perception is that this level of GIA being off on the fluorescence-grade is mostly an event of the last two years. Before that, we considered them acceptable in this grade. That has unfortunately changed, and it has a side-effect on the wholesale-market. Before 2016, there was hardly a discount for a GIA-Faint compared to a GIA-None. Nowadays, it is clear that wholesalers have to sell GIA-Faint with a discount.

As far as fluorescence-grading of AGS goes, I must state that our experience is colored, as our experience with AGS is limited to us sending our own production there. Now, in production, we wish to avoid receiving an accidental Medium-grade since a few years and we thus use a 'safe' internal fluo-grade to make sure that we are in the high end of Negligible. As such, I cannot comment on how far 'down' the Negligible-grade of AGS goes, as we are not 'testing' that boundary.

In summary, our team from experience does not trust the current GIA-grade of fluorescence. We cannot really comment if the AGS-grading is better or worse, simply because of lack of experience.

In this thread, however, I found Garry's post very interesting and worthy of a further discussion. Since this thread already went in a totally different direction, I suggest starting up a new thread regarding Garry's topic.

Live long,

Thanks Paul, but i think the appropriate place is the very long running thread started by Michael Cowing as there is so much info there.

And everyone else - you really need to stop fretting as the rules are being changed. GIA is surely going to or already has moved to the near visible much longer wave UV because it does create stronger UV. On top of that new research is pointing to the benefits of Fluoro given labs have now changed their lamps and distances to the lamps so the 'over grading' that Cowing et al panic about was a 15 year old story.
Here is an excerpt from HRD - the top European lab's research
"As an example, a diamond graded in the HRD Antwerp laboratory as a J color with very strong fluorescence can appear as a D color when examined in outdoor conditions. When the diamond is examined through the table (face up), there is still an improvement in color, although this change is less significant."

 

[Garry H (Cut Nut)]

For the record - here is a GIA patent application from 2016 that I refered to that has been granted 6 weeks ago.
https://patents.google.com/patent/U...signee=Gemological+Institute+Of+America+(Gia)
Search for 365 and 385 and you will see that I am not dreamin!

 

[Texas Leaguer]

@Paul-Antwerp
I would agree with one of your statement - everybody speaks based of his own experience!
All my 15sh GIA - USA - New York graded diamonds I can say have absolutely accurate grade of fluorescence. As GIA is international lab, and my own diamonds are very limited number, I cannot judge in general, then.
After purchasing few AGS diamonds I realized I cannot trust this lab in regard of fluorescence.
Everybody is free to have his own opinion, based on his own experience.

@EvaEvans ,
Just to make sure we are on the same wavelength , you do understand that AGS and GIA have different approaches right? The AGS term "negligible" is not the same as the GIA term "none". This is a common misunderstanding. The AGS term subsumes both inert and faint+. Therefore, by definition the diamond can have fluorescence, and only when it reaches a level of medium does it get reported as such. Another difference in approach is that AGS observes fluoro in the face up direction as opposed to the GIA method of observing table down from the side. Since fluorescence can sometimes be directional, this can result in a different observation between the labs.

The logic in the AGS approach is that there is negligible impact of fluorescence below medium. GIA's own observational studies have concluded the same.

In our experience looking at thousands of AGS graded diamonds each year, it is rare that we see a diamond reported as negligible that we feel reaches a strength of medium, but there have been those occasions. Even though fluoro masters are used, just like color or clarity, the final call is made by a human grader. Thus, borderline situations can go either way.

 

[EvaEvans]

@Texas Leaguer
I understand very well that the AGS "negligible" fluorescence suits very well the business, but mislead the customer! "Negligible" is somewhere between none, faint and medium fluorescence. But in a diamond search such AGS certified diamond will appear only in "Fluorescence: NONE" category!
365nm wave length is the standard in gemology, so even me, as a non-professional, at home environment, I can measure accurate if there IS or there ISN'T fluorescence, so I don't see why AGS can't!
The term "negligible" is just an OPINION of the AGS lab, but I would prefer to be an informed customer and I would like to know if at 365nm there is, or there isn't fluorescence!
I feet it WRONG that the AGS prefer to use the term "negligible" even when some level of fluorescence is presented!
I feel much more comfortable to know the FACT, not the OPINION.
I can only agree with you at the point the the fluorescence LEVEL could be subjective! But the existence, or absence of fluorescence at 365nm have to be objective!

 

[Garry H (Cut Nut)]

@Texas Leaguer
I understand very well that the AGS "negligible" fluorescence suits very well the business, but mislead the customer! "Negligible" is somewhere between none, faint and medium fluorescence. But in a diamond search such AGS certified diamond will appear only in "Fluorescence: NONE" category!
365nm wave length is the standard in gemology, so even me, as a non-professional, at home environment, I can measure accurate if there IS or there ISN'T fluorescence, so I don't see why AGS can't!
The term "negligible" is just an OPINION of the AGS lab, but I would prefer to be an informed customer and I would like to know if at 365nm there is, or there isn't fluorescence!
I feet it WRONG that the AGS prefer to use the term "negligible" even when some level of fluorescence is presented!
I feel much more comfortable to know the FACT, not the OPINION.
I can only agree with you at the point the the fluorescence LEVEL could be subjective! But the existence, or absence of fluorescence at 365nm have to be objective!

365 has nothing to do with anything in the world other than that was a frequency that people thought (wrongly as per the 2013 study) they could produce consistently.
there is very little 365 in the real world (not in light sources and removed by windows etc) and way more from 385 upwards (which is abundant in many light sources and passes through windows).

 

[EvaEvans]

@Garry H (Cut Nut)
At 365nm or 385nm the existence or absence of fluorescence will NOT change, just the intensity will be less or more!
What I wanted to say is that a precise wave length have to be used when we make comparison!

 

[EvaEvans]

@Garry H (Cut Nut)
I may agree with you, that in term of diamonds, the better UV wave length should be the 385nm as it's more close to the visible spectrum, and thus will have more impact to the diamond performance.

 

[Diamond_Hawk]

I love our trips down the fluorescence rabbit hole!


^^That's a strong blue hole right there!

 

[Johnbt]

For the geeks among us this is great reading...

www.gia.edu/gems-gemology/summer-2013-luo-fluorescence-optical-defects

"The combination of 3D fluorescence spectra from common defects and emission spectra from several standard ultraviolet light sources revealed noticeable inconsistencies in the fluorescence observed."

"Each 3D scan took approximately four hours to complete and consisted of 57 individual spectra."

At least they included one pretty picture with all that dry science. (I think I'm going to have to make another pot of coffee to get through the entire report. The joys of retirement.)

 

[Garry H (Cut Nut)]

@Garry H (Cut Nut)
At 365nm or 385nm the existence or absence of fluorescence will NOT change, just the intensity will be less or more!
What I wanted to say is that a precise wave length have to be used when we make comparison!

It is vitally important Eva.
365 is blocked by windows and is absent in lighting.
380 > is abundant (less so in LED) and not blocked by windows.
So the whitening effect is happening to +medium blue diamonds all around us.
Now that GIA et al use low UV emission lamps and a greater controlled distance for color grading, and machines and digital devices, it is safe to assume that they are not overgrading color as they were 15-20+ years ago.
They are UNDERgrading which is a benefit to savvy buyers.

 

[EvaEvans]

So the whitening effect is happening to +medium blue diamonds all around us.

So, Garry, you assume only the POSITIVE effect of the fluorescence, but I'm thinking of the possible negative effect too!
Also, when I said that 365nm or 385nm will not change the result, I was meaning that 20nm difference will not affect the existence or the absence of fluorescence. The change could be only in the level of fluorescence intensity.
So, my point of thinking is, that the buyer should be trustfully informed if the fluorescence is "none" or "some", that's why I do not accept the AGS term "negligible".
Garry, if for you, as a professional in the diamond business, the UV wave length has a significant impact to the lab certification result, so why the labs don't have a standard about the measuring of the fluorescence? Why the measuring of color and clarity is standardized, but the measuring of fluorescence is not?

 

[Texas Leaguer]

So, Garry, you assume only the POSITIVE effect of the fluorescence, but I'm thinking of the possible negative effect too!
Also, when I said that 365nm or 385nm will not change the result, I was meaning that 20nm difference will not affect the existence or the absence of fluorescence. The change could be only in the level of fluorescence intensity.
So, my point of thinking is, that the buyer should be trustfully informed if the fluorescence is "none" or "some", that's why I do not accept the AGS term "negligible".
Garry, if for you, as a professional in the diamond business, the UV wave length has a significant impact to the lab certification result, so why the labs don't have a standard about the measuring of the fluorescence? Why the measuring of color and clarity is standardized, but the measuring of fluorescence is not?

If you read the 2013 GIA study you will understand why standardization has so far been an allusive goal. Not only are all the excitation devices different from one another in their outputs, but even the same device will have different output depending on age of tubes, leakage of filters, etc. Combine that with the fact that diamonds sometimes have multiple defects that cause competing emissions within the diamond. The emissions of one defect can even provide excitation in another defect which can stimulate a stronger emission than the primary source itself. That is all to say, the subject is far from simple. And the percentage of diamonds with no defects (that would always be inert or 'none' is very, very small.)

Given current technology, the AGSL reporting approach actually makes more sense. Perhaps the new GIA system which Garry linked the patent application will help to standardize fluoro reporting. Time will tell.