Article Over Grading of Blue Fluorescent Diamonds Revisited

[drk14]

Experiment 2:

Required Materials:

• One or more diamonds, with non-negligible fluorescence.
• One black light (or similar LWUV light source).
• Tonic water.
• UV-blocking safety glasses (depending on the strength of your UV light source)

Procedure:
In a darkened environment, place the diamond(s) and tonic water next to each other, and illuminate with UV light. Compare the relative intensity of the tonic water and diamond. Bonus points if you can estimate the equivalent GIA fluorescence grade of the tonic water.


I would really appreciate if someone could actually do this experiment and report back, as I cannot currently perform this test for myself (as the only fluorescent diamonds that I have access to are ungraded melee stones)!

Feel free to also report your results from Experiment #1...

 

[Texas Leaguer]

Brilliant demo!

I think I will order a gin and tonic next time I am in a night club! Great conversation piece.

 

[drk14]

Brilliant demo!

I think I will order a gin and tonic next time I am in a night club! Great conversation piece.

I'm hoping somebody will actually try these experiments and report back (especially Experiment #2, which I cannot do myself, unless someone wants to donate a strong blue fluorescent diamond to science...). Maybe a poll thread in Hangout would help.

Bryan, if the bar has any barrel-aged gin for your G & T, you'll be able to try a very interesting experiment (relevant to the core question of this thread). Stay tuned for Experiment #3...

 

[OoohShiny]

haha I always wondered why G&T glowed in a club

Just to say, you're pretty awesome, @drk14, keep up the good work!

Your input and plain-English explanations are much appreciated

 

[Rockdiamond]

To echo OoohShiny- you are truly awesome drk14!!
I've been a bit too busy to be able to perform the experiments - but I intend to next week.
By any chance are you ever in NYC drk14?

 

[drk14]

Thank you for the kind words, guys...

I've been a bit too busy to be able to perform the experiments - but I intend to next week.
By any chance are you ever in NYC drk14?

I'm a few hours from NYC, but don't visit that often. I actually visited you at DBL in the summer of 2016, which is the last time I was in the city.

I'm glad to hear you will try the experiments, and look forward to seeing your results!

 

[Rockdiamond]

Wait.....what..we've met each other??
How kewl is that!

 

[drk14]

Wait.....what..we've met each other??
How kewl is that!

Haha! Yes, I wanted to see some of your pinfire diamonds after all of our online discussions about crushed ice, and I also wanted to take a look at a pink diamond ring that you had recently listed.

 

[Karl_K]

Not sure if I posted this already,
Observing more or less color is also highly lighting related not just uv/fl.
Look at something colorful under: sunlight. florescent light, led, standard bulbs, reveal light bulbs and other high cr bulbs.
For example a blueish white led or florescent could make a different color shift in a yellow diamond vs a grey or brown one. Even different shades of the same color could be affected differently.
No UV light/FL is not the only lighting capable of masking color.
On the other hand there are also several lighting types that would pop yellow more than other colors also.
Also the old diamond grading bulbs shifted tone as they aged.
Daylight also varies on a variety of factors.
Reminds me of my old saying, the top 5 things affecting a diamond appearance:
lighting
lighting
lighting
lighting
lighting

 

[Rockdiamond]

Not sure if I posted this already,
Observing more or less color is also highly lighting related not just uv/fl.
Look at something colorful under: sunlight. florescent light, led, standard bulbs, reveal light bulbs and other high cr bulbs.
For example a blueish white led or florescent could make a different color shift in a yellow diamond vs a grey or brown one. Even different shades of the same color could be affected differently.
No UV light/FL is not the only lighting capable of masking color.
On the other hand there are also several lighting types that would pop yellow more than other colors also.
Also the old diamond grading bulbs shifted tone as they aged.
Daylight also varies on a variety of factors.
Reminds me of my old saying, the top 5 things affecting a diamond appearance:
lighting
lighting
lighting
lighting
lighting

BINGO!!
Even sunlight is totally different at different times of the day.
Imagine a Chestnut Mare - the perception of color at dawn, is totally different than at noon.
As it relates to the "whitening debate"- there's undoubtedly other lighting variations that impact the phenomenon.

Byran- say we stipulate the there's 0 UV when you're indoors, in a room with indirect/reflected sunlight.
Yet whitening has been observed by 60% in the 1997 Moses study.
There must be other causes.

This is from the original article
"In daylight, additional factors, including time of day, geographic location, and whether or not the day was sunny or cloudy cause the color of a fluorescent diamond to change."
I agree with the premise that Fluorescence complicates grading for GIA.
I disagree that the problem is fixed by changing lighting.
Fluorescence varies from stone to stone in the manner in which it impacts color perception
Basically, there's simply no way GIA can be right on the color grading of Stong Fl diamonds all the time due to individual variances
It's just one of the many physical characteristics of diamonds that makes them totally unique, and special.
Diamonds have impacted every area of our lives due to these characteristics.
From the gas in our tanks ( drill bits) to the screen in our smartphone, which is polished using a diamond abrasive- to microprocessors - which are cooled by microscopic diamonds. Diamonds have changed our world.
And of course, nothing looks quite like a polished diamond.

The point is, fluorescent diamonds play with the light in ways which we may not be able to fully identify scientifically....yet.

 

[Rockdiamond]

Fluorescence Experiments...

Ok, so why am I having you study beverages from the supermarket? And what does this have to do with fluorescent diamonds?

It turns out that tonic water contains quinine molecules, which are fluorescent:



This should be a pretty good model for blue fluorescence in diamonds caused by N3 centers, because the concentration of N3 centers in fluorescent diamonds is similar to the concentration of quinine in tonic water, and the quantum efficiencies of N3 and quinine are also similar. Moreover, the excitation and emission spectra for quinine in tonic water bear a significant resemblance to the corresponding spectra for N3 fluorescence in diamond. Here are the 2D and 3D spectra for tonic water (measured by a Jasco FP-6500 spectrofluorometer, an instrument similar to the ABII used in the Luo & Breeding 2013 paper):



These spectra show that the quinine fluorescence in tonic water is excited by wavelengths in the range 300-410 nm (LWUV and some visible violet), and emits fluorescence in the range 380-600 nm (with a peak around 455 nm, which is blue).

Compare to the N3 excitation and emission spectra from Luo & Breeding (2013):



Based on the above, I hypothesize that the appearance of fluorescence in tonic water under LWUV and/or VV excitation will have a similar appearance (both in hue and intensity) to diamonds with blue fluorescence!

This brings us to...Experiment #2, described in the next post.

I'll be shopping later...I need to buy Tonic water ( in a clear bottle) yes?

 

[drk14]

I'll be shopping later...I need to buy Tonic water ( in a clear bottle) yes?

Yes, for Experiment #2, you will definitely need tonic water. I would suggest a clear plastic bottle, but if such containers are not available, you could pour the tonic water into a cup or a shotglass when you do the experiment.

However, to do Experiment #1, you will also need a bottle of club soda and/or seltzer water as a control group. It is best if all bottles are clear and have the same shape (as shown in the picture in post #599), but if the bottles look different, you can always pour the liquids into glasses or other containers that have similar shape.

For Experiment #3 (which I haven't posted yet), you will additionally need some kind of clear orange/yellow or amber liquid that is miscible in water (e.g., apple juice, tea, barrel-aged gin, etc.).

 

[Texas Leaguer]

BINGO!!
Even sunlight is totally different at different times of the day.
Imagine a Chestnut Mare - the perception of color at dawn, is totally different than at noon.
As it relates to the "whitening debate"- there's undoubtedly other lighting variations that impact the phenomenon.

Byran- say we stipulate the there's 0 UV when you're indoors, in a room with indirect/reflected sunlight.
Yet whitening has been observed by 60% in the 1997 Moses study.
There must be other causes.

This is from the original article
"In daylight, additional factors, including time of day, geographic location, and whether or not the day was sunny or cloudy cause the color of a fluorescent diamond to change."
I agree with the premise that Fluorescence complicates grading for GIA.
I disagree that the problem is fixed by changing lighting.
Fluorescence varies from stone to stone in the manner in which it impacts color perception
Basically, there's simply no way GIA can be right on the color grading of Stong Fl diamonds all the time due to individual variances
It's just one of the many physical characteristics of diamonds that makes them totally unique, and special.
Diamonds have impacted every area of our lives due to these characteristics.
From the gas in our tanks ( drill bits) to the screen in our smartphone, which is polished using a diamond abrasive- to microprocessors - which are cooled by microscopic diamonds. Diamonds have changed our world.
And of course, nothing looks quite like a polished diamond.

The point is, fluorescent diamonds play with the light in ways which we may not be able to fully identify scientifically....yet.

It’s clear to anyone who has ever spent any time looking at a diamond that it looks different in different lighting environments. So I agree with Karl that diamond appearance revolves around ‘lighting, lighting, lighting…’ The issue here is to what extent blue fluorescence masks yellow body color in different lighting environments. And that is the point of drk’s tonic vs seltzer experiment.

It is well documented that whitening takes place in direct sunlight and in very close proximity to fluorescent grading lights, both scenarios where UV intensity is very high.

The question is whether whitening takes place under typical lighting scenarios where most consumers spend the majority of their time. The studies show that the dropoff in intensity of UV wavelengths even a foot or so away from grading lights is too weak to stimulate color whitening fluorescence. If the reaction is weak, the emitted blue wavelengths will be overwhelmed by the wavelengths of the stimulating source and whitening cannot be perceived. (drk14 methodically walked us through the science of this, including an analysis specific to Garry’s VV assertion). The Moses survey likewise concluded that average observers (consumers) detected no difference in body color among diamonds of the same color grade and differing strengths of blue fluorescence.

Does color whitening happen in some diamonds in some lighting scenarios? Very likely. Are there reasons other than fluorescence that could account for this? Probably. But the whitening would therefore not be specific to fluorescent diamonds.

My takeaway- labs need to take simple precautions to prevent overgrading due to the color masking effects of blue fluorescence in the grading environment. And consumers should NOT expect blue fluorescent diamonds to look whiter than their color grade. In fact, based upon the studies of Cowing, Tashey, et al, they should double check them for overgrading.

 

[Rockdiamond]

Does color whitening happen in some diamonds in some lighting scenarios? Very likely. Are there reasons other than fluorescence that could account for this? Probably. But the whitening would therefore not be specific to fluorescent diamonds.

Progress!!
Bryan, what if the other reasons causing the whitening are directly related to the fluorescence?
It's possible that a percentage of inert diamonds might have a similar characteristic.
This actually sounds plausible. Without a doubt, there's cases of two diamonds (inert) that grade the same through the pavilion, yet one faces up whiter than the other. It's possible that this as of yet unknown characteristic combines with the fluorescence to case face up whitening.

 

[Texas Leaguer]

Progress!!
Bryan, what if the other reasons causing the whitening are directly related to the fluorescence?
It's possible that a percentage of inert diamonds might have a similar characteristic.
This actually sounds plausible. Without a doubt, there's cases of two diamonds (inert) that grade the same through the pavilion, yet one faces up whiter than the other. It's possible that this as of yet unknown characteristic combines with the fluorescence to case face up whitening.

It's more likely to be defects unrelated to fluorescence, though they may be present in a higher percentage of fluoro stones for some reason. That is pure speculation on my part. As I mentioned earlier, in my experience I have noticed graining and twinning in a lot of fluoro stones. These features can affect transparency to some degree. Opacity can be perceived as whiteness. Think of "white out" conditions on a ski slope.

Unfortunately, if this is an operative factor, it is not a desirable one in my opinion.

 

[Karl_K]

The biggest problem is that the studies are small with small sample size, non-random, and to small a group of people looking and are not double blind.
There for a scientifically accurate conclusion is not possible but its fun playing around.
Now my opinions:
In some color ranges grade creep is possible due to UV including 400nm in the lighting used.
I am highly doubtful that it is enough to move the grade more than a fraction of a color ranges below maybe H. There may be exceptions.
Observed color is more dependent on overall lighting and eyesight than UV except in high UV lighting with strongly reactive stones.
UV provides a way kewl effect in highly reactive stones.
UV as graded by the labs is not a highly accurate picture of the overall reaction to UV in some diamonds.

 

[Rockdiamond]

Byran, I can understand where you're coming from, regarding transparency.
Let me pose the question to you… Does more light come out of a D color diamond then a J colored diamond?
Is it "more transparent"

 

[Karl_K]

I am also incredibly curious if micro-inclusions could explain over blues as discussed earlier.

 

[Karl_K]

Byran, I can understand where you're coming from, regarding transparency.
Let me pose the question to you… Does more light come out of a D color diamond then a J colored diamond?
Is it "more transparent"

Yes to some degree in my opinion. Not a huge amount however.
Certainly a dark brown or back is less transparent than a D or J by a noticeable factor.
The thing is diamonds are sorted by color at the higher ranges to a degree that would be considered noise in say paint colors.

 

[Texas Leaguer]

Byran, I can understand where you're coming from, regarding transparency.
Let me pose the question to you… Does more light come out of a D color diamond then a J colored diamond?
Is it "more transparent"

Technically yes. Some light energy is being absorbed in the J that is not being returned to your eye.

 

[Karl_K]

Byran, I can understand where you're coming from, regarding transparency.
Let me pose the question to you… Does more light come out of a D color diamond then a J colored diamond?
Is it "more transparent"

micro-inclusions below grade levels in a flawless graded stones have some impact on transparency also if you want to get super technical.

 

[Rockdiamond]

UV as graded by the labs is not a highly accurate picture of the overall reaction to UV in some diamonds.

OMG is that ever true- especially in fancy colors. The stuff I wrote about diamonds above.. .they are truly unique and special. It's easy to prove this scientifically.... but there's some aspects that are kind of ...mystical. They are very special rocks

We all agree that we could prove scientifically that less light is coming out of a D than a J.
Bryan, it seems to me that there can be no other reason besides transparency which will cause less light to come out of the diamond.
ie, a D is more transparent than a J.

Say we are comparing elephants.
One weighs 20,967 pounds.
The other, clearly heavier, from a scientific standpoint, weighs in a 20,968 pounds.
I'm sure you get where I'm going here.

 

[Karl_K]

We all agree that we could prove scientifically that less light is coming out of a D than a J.
Bryan, it seems to me that there can be no other reason besides transparency which will cause less light to come out of the diamond.

Just my opinion there are 20? maybe 30? factors that make a bigger difference than D vs J in comparing 2 diamonds light return.
Now if the impossible was done and the only difference was the color then .......

 

[Rockdiamond]

Karl, since it's a theoretical argument in any event- let's stipulate two diamonds, identically cut. Same size.
Both Flawless. One's a D and one's a J. the J emits less light.
Or, two identical diamonds, one a D/Flawless, the other D/VVS1.
The minuscule imperfection has to block some light.

My point is that the difference in transparency, although real, is insignificant enough as to be completely meaningless.
I agree that there is a component of the whitening which is related to transparency. But the effects are actually seen as a positive- which is entirely the point.
The "Premier" type of stones from my Winston days- you could spot them. Still can. The reason may be an insignificant lessening of transparency.
In a D, it results in a blue-ish cast- in a J the blue translates to whiter.

 

[Texas Leaguer]

I'm hoping somebody will actually try these experiments and report back (especially Experiment #2, which I cannot do myself, unless someone wants to donate a strong blue fluorescent diamond to science...). Maybe a poll thread in Hangout would help.

Bryan, if the bar has any barrel-aged gin for your G & T, you'll be able to try a very interesting experiment (relevant to the core question of this thread). Stay tuned for Experiment #3...

I finally got some time and have been playing with experiment #1. I have enlisted my staff in a blind survey. I took off the labels and marked the tonic water discretely.

So far, all of the staff could see a difference in the body color of the two liquids. The tonic water is seen as being less colorless than the soda. Estimates range from a single color difference to 4 or 5. General consensus is that if the Soda is in the colorless range (DEF), then the tonic would be in the near colorless (GHIJ).

With regard to the fluorescence of the tonic water, most put it at medium to strong blue.

It's a little tricky on both color and fluoro estimates because the scale is so much bigger. But we're having fun with it!

 

[drk14]

I finally got some time and have been playing with experiment #1. I have enlisted my staff in a blind survey. I took off the labels and marked the tonic water discretely.

Bryan,
This is great, thanks for taking the time to do this, and for posting your observations. I've been traveling and working on an NIH proposal, so I haven't had a chance to respond until now.

General consensus is that if the Soda is in the colorless range (DEF), then the tonic would be in the near colorless (GHIJ).

This is very interesting. Frankly, I would not have expected either beverage to register any body color, but it would make sense that that the tonic water has some yellowish tinge to it, given that the quinine absorbs some of the available violet light.

With regard to the fluorescence of the tonic water, most put it at medium to strong blue.

Great, this confirms my hypothesis that tonic water is a good model system for studying the effects of blue fluorescent diamonds.

It's a little tricky on both color and fluoro estimates because the scale is so much bigger. But we're having fun with it!

You could ameliorate the scale disparities by pouring the liquids into shot glasses (or, if you really want to science it up, order yourself some cheap test tubes).

Stay tuned for Experiment #3...

 

[drk14]

Experiment 3:

Required Materials:

• Tonic water.
• Club soda or seltzer water.
• Ice tea or apple juice (or any other orange/amber-colored, but high-clarity liquid).
• At least 2 clear cups (or other containers) of the same size and shape.
• Marker and/or marking tape.
• Preferrably: Measuring tools (e.g., measuring cups, measuring spoons, balance, or pipette).

Procedure:

1. Mark the 2 cups "A" and "B" (or "X" and "Y", etc.) using the marker and/or marking tape.
2. Dispense an equal volume of the colored liquid into each cup.
3. Dilute the liquid in one of the cups using the club soda (or seltzer), until the apparent body color resembles that of an J/K diamond, keeping track of how much liquid was added. This cup is the control; make a note of which cup ("A" or "B") was used as the control, but keep this information secret.
4. Dilute the other cup using the tonic water. Add a volume equal to the volume of club sode or seltzer water that was added to the control cup (do not use the apparent body color to determine how much tonic water to add!). Confirm that the liquid level is identical in both cups.
5. Now the fun part: Ask one or more test subjects to judge whether there is any apparent difference in the body color of the two liquids, and if so, which one has less apparent body color. Repeat in different lighting conditions (indirect/direct sunlight, fluorescent lights, etc.).

Notes:

• I have suggested diluting to a J/K color, to allow comparison to some of the experiments performed by Moses et al. (1997). If there is time and interest, the whole experiment can be repeated using a different color grade for the control liquid, to see if there is any difference in the test results.
• To compensate for effects of chance, you can do a variation of this experiment, in which you dispense the liquid from each cup ("A" and "B") into many smaller containers (e.g., shot glasses or test tubes) that are randomly numbered, and keep a (hidden) record of which liquid ("A" or "B") was poured into each of the smaller containers. Ask your test subjects to sort the liquids in order of ascending body color, and then record which containers were ranked in the top (less color) 50% and which containers were ranked in the bottom (more color) 50%. For this variation of the experiment, you may need to mix the original control liquid to a darker color (maybe M/N), to compensate for the fact that the color absorption will be less when the liquid is transferred into smaller containers.
• Because Bryan's results from Experiment #1 suggest that the tonic water may have some perceptible body color by itself, I may have to come up with a modified experimental design to account for this potentially confounding factor. Stay tuned for more science...

 

[Rockdiamond]

Good work Bryan!!
DRK- I apologize for my absence.
I've also had tons of stuff on my plate preventing me from participating in the experiment.
But I'm watching with interest.

 

[Texas Leaguer]

Here's a picture of the soda and tonic in shot glases under a UV lamp along with a 2ct diamond of medium fluorescence.
I find it kind of interesting that when viewed in the smaller amounts, the body color difference between the two liquids became much less noticeable (but still there), while the fluoro strength was about the same. This may suggest that in lighting scenarios where color masking can occur, small stones may benefit more than big stones. (??)
As you can see, the tonic water is glowing pretty bright. I would say it is stronger than medium. It does not look as blue in the photo as it does in real life. I think it may be slightly overexposed in the photo because everything else was so dim.

 

[drk14]

Bryan - great photo, thanks for posting it!

I find it kind of interesting that when viewed in the smaller amounts, the body color difference between the two liquids became much less noticeable (but still there),

This is explained by the Beer-Lambert law (the absorption decreases with decreasing pathlength). I would expect the fluorescence to also decrease with decreasing pathlength, maybe the brightness of the fluorescence makes it more difficult to notice the intensity change?

FYI, I have an idea for modifying Experiment #3 to account for the effect of the body color in the tonic water, but I haven't yet had a chance to test it. This is the experiment that will show whether or not fluorescence can improve body color in "real life" viewing conditions. Stay tuned.