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Should we discourage or recommend FL stones?

Garry H (Cut Nut)

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Garry,
The fact that alternate technologies exist or new technologies emerge does not necessarily invalidate older studies. You have mentioned numerous times that in your opinion the Cowing study used the wrong device to measure light content or intensities, and that it was focused on the wrong wavelength. Could you explain how that invalidates what the study reveals? Or the study's conclusions and recommendations?
I have previously shown the graphs Bryan, read back. Frustrated! Not going to re-answer this other than to say that an ordinary photographic light meter is better at measuring the causative radiation than the UV meter Cowing used.

Afterall, the study was done in response to an issue that many in the trade had already identified and were concerned about. The study itself involved a survey of diamonds with varying degrees of fluorescence and attempted to establish the problem, explain the root cause mechanisms, and make recommendations to solve or mitigate the problem.
He did less to bring about change than Marty Haske. By 2008 it was 8 years too late.

The issue was considered of sufficient importance that many serious people in the trade (Martin Rapaport among them) attributed the unwarranted discounts (value loss) of fluorescent diamonds largely to the color grading problem.
So you have not read rapaports latest article, clearly. It is 2 weeks old. Total back flip from Rapaport.
365nm was used in the study because it was (and still is) the standard used in the labs for observing and reporting the fluorescent reaction. You never read about GIA's color grading patents that I have posted Bryan? Seems more like 385 is the number now.
But it was also called out in the study that other wavelengths excite blue fluorescence, in particular wavelengths from 380-415 in the Visible Violet band of the spectrum. Thomas Hainscwhang’s 3D graph shows the different wavelengths and the strength of their effects. So the impact of VV is not ignored in this study, in fact it was highlighted. Yet MC used a UV Solarmeter that does not read those frequencies?

But what difference does that make to the findings of the study? Grade whitening was observed in various lab grading environments and correlated to both the strength of fluorescence (observed at 365) and to the intensity/distance from the light source. 365 nm, VV and all wavelengths in between obey the same laws of physics and will similarly lose intensity and their fluorescence stimulating ability within a few inches of artificial light sources. You are wrong.

Much of your position on the visual impact of fluoro seems to center around environments with varying degrees of sunlight present. But the diamonds in the Cowing study were not graded in sunlight, nor were the stones in the GIA survey. Bryan why cant you stop writing and do something to see for yourself?

While doing a study on the visual impact of fluorescence on diamonds where varying intensities of sunlight are present is a worthwhile idea, that is not what Cowing et al studied. And it is not constructive to malign their work because they didn’t choose a different question to study and/or different measuring devices and wavelengths.
Do you know what CRI means Bryan? Can you color grade diamonds under your desk?
 

AV_

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Another way to convey approx. colourless colour in transparent prisms via photography: www

I'm guessing there was some photomicrography or other microscopy experience at play, to begin with.
 
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Rockdiamond

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Hi @sledge
I’m not sure which logic you’re declaring is broken.
The graphs and technical data cloud some of the important information we’re discussing to many of the consumers reading this. There’s no need to become a physicist to understand these issues.
Basically my position has been that no matter what the color grading method is chosen by the lab, it will involve compromises that ultimately lead to some level of real-world inconsistency. Particularly true in the case of fluorescent diamonds.

@Garry H (Cut Nut) would it be possible for you and some of the vendors such as WF, CBI and others to put together a new study concerning fluor?

For me I see two main issues:

1. The effects during color grading in a controlled lab.
2. The effects after grading in the real world.

It seems like addressing item #1 would be fairly simple and not too terribly expensive. Better yet, is this a study that vendors want to give involved in doing as I'm sure there could be some negative blow back as well.

At least it sounds simple. Use the correct meter you've mentioned. Take readings using various bulbs under various conditions (7" away, 10" away, 12" away, filters, etc).
I have done extensive real-world work on your point number two above- likely far more and for longer than anyone else participating. I'm the buyer for our company and have been for 20 years- close to 100 million dollars of loose diamonds purchased- by me.
In the real world, sufficient light is needed to observe slight differences in color. Specially not bright jewelry store lighting. While GIA needs to use a clinical methodology ( or machines) that exclude daylight- most people in the trade use daylight, combined with fluorescent lighting. Daylight, not direct sunlight.

The physical characteristics are not in doubt to anyone with eyes and a diamond. The color change certain fluorescent diamonds exhibit is easy to see if one has the proper lighting and type of blue fluorescent stone Garry and I are referring to.
I have experienced what Garry has documented in this thread- a GIA graded G which faced up much whiter. On countless occasions over many years.
I don’t grade color in lab conditions- I can’t afford to. I’m putting my butt on the line when we buy diamonds. My concern is how does the diamond actually face up. Kind of like a consumer.
Except I might buy 20 diamonds in a day. And have been doing so for many years. While I’m not concerned with how GIA gets to the grade, I’m extremely familiar with the real world implications of the grade. How it affects price.
The odd aspect here is Bryan trying to use some sort of data to prove to Garry and I (and a whole lot of folks in the diamond business) that what we see with our own eyes is somehow not possible.
Garry has responded on multiple occasions answering Bryan’s specific scientific questions. Byran will pick something I write to insult or contradict me- then never defend his position.
 
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Texas Leaguer

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A bit tangential, but anyone who has followed this thread to this point probably will find this news report interesting:
 

OoohShiny

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A bit tangential, but anyone who has followed this thread to this point probably will find this news report interesting:
That is fascinating. thank you for posting it! :)) I'm going to post it in the MMD forum as well!
 

Rockdiamond

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I hope it's ok- I borrowed this from another thread.
In the second paragraph, GIA states first that "GIA studies show that, for the overwhelming majority of diamonds, the strength of fluorescence has no widely noticeable effect on appearance"

The very next sentence GIA says:
"In many cases, observers prefer the appearance of diamonds that have medium to strong fluorescence."

Does anyone else notice a total contradiction here?

Bryan- how in the world does synthetic diamonds reaction to UV have anything to do with what we're discussing?
 

Garry H (Cut Nut)

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1576020670143.png

It is not possible to detect subtle color differences in poor light.
In good lighting there is a whitening effect on strong blue fluorescent diamonds because whitening comes more from visible and near visible part of the spectrum than it does from the very short wave radiation that labs used to grade fluorescence.
 

Texas Leaguer

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Running away from what?

Garry, thanks for answering my questions. But if I don't seem persuaded it's probably because I am not.

The good thing is, you put it out there and other readers can make up their own minds.
 

sledge

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1576020670143.png

It is not possible to detect subtle color differences in poor light.
In good lighting there is a whitening effect on strong blue fluorescent diamonds because whitening comes more from visible and near visible part of the spectrum than it does from the very short wave radiation that labs used to grade fluorescence.
I'm confused.

Are you saying 60 is a level that is too poor of lighting that I should not be able to detect subtle color differences?

Because I can see variation not only between color groups (yellow, red, green, etc) but also between the hues in each color group (yellow, gold, etc) at the 60, 80 and 90 levels.

I'm not straining to see difference at 60, so could probably go much lower.
 
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Rockdiamond

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Bryan- what exactly are you not convinced of?
Garry and I are sharing actual real life experiences with diamonds, both fluorescent and inert.
Garry is sharing technical details explaining why we see what we see.
Apparently you haven't seen it.
I believe you have not seen it.
There are so many reasons why you might not have witnessed whitening.
The fact you have not seen it does not mean it does not exist.
But please consider that both Garry and I respect you. I can only speak for myself, but I like to read your ideas ( mostly) and I'm glad we participate together here.
Knowing Garry, I'd wager he feels the same.

So I ask again- do you think we're both making this up? Could you at least allow for the possibility that we are telling the truth?

@sledge - say you were buying a diamond, that didn't have a GIA report- and had to base the purchase on your own two eyes determining the color- would you want 60 or 90 lighting conditions?
You're assuming that the differences in shade in Garry illustrations are anything as subtle as the difference between a D and an E. They are not. The difference between D and E is so very slight. Color grading a diamond requires a lot of light.
 
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Garry H (Cut Nut)

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I'm confused.

Are you saying 60 is a level that is too poor of lighting that I should not be able to detect subtle color differences?

Because I can see variation not only between color groups (yellow, red, green, etc) but also between the hues in each color group (yellow, gold, etc) at the 60, 80 and 90 levels.

I'm not straining to see difference at 60, so could probably go much lower.
There is no way in lower lighting levels that anyone can identify the difference between an I and a D.
 

diamondsR4eVR

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There’s a lot of pages here...what’s the best lighting to measure a K color with strong fluorescence? Cloudy day? Direct sun? Although, I’ve heard direct sun can make a great cut stone look not so great.
 

Karl_K

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There’s a lot of pages here...what’s the best lighting to measure a K color with strong fluorescence? Cloudy day? Direct sun? Although, I’ve heard direct sun can make a great cut stone look not so great.
For a consumer every lighting revilement you find yourself in including direct sun. Direct sun is more about the light show it casts around it than looking directly at the stone. Sunlight thru a car window and looking at the light show it projects on the inside of the car is one of the best light shows imho.
 

sledge

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There’s a lot of pages here...what’s the best lighting to measure a K color with strong fluorescence? Cloudy day? Direct sun? Although, I’ve heard direct sun can make a great cut stone look not so great.
What is your goal? Meaning, are you trying to determine if a stone is hazy/cloudy because of the strong fluor? Or are you wanting to see if it turns a bluish hue? Or maybe if you are just wanting to see how it may whiten in optimal conditions? Or...or....or.

You get my point.

Depending what you are trying to achieve, the answers may vary. For instance, viewing a stone in direct sunlight will theoretically expose it to the most UV radiation which then cause the stone to fluorescence. In this condition, you could see that bluish hue. Also, if the fluor creates that hazy look, it would be most prevalent in this condition.

Even when viewing outside, you have to consider if it's direct sunlight or cloudy or the time of day, etc.

Have you seen this thread yet? I don't think you'd have the same result, but it shows what a very strong blue fluor in a D stone can change in various lighting conditions.


There are more pictures, but here are a few I thought you may find interesting.

Cloudy rainy day/indirect sunlight:
1576042714122.png

Same cloudy rainy day near window:
1576042923450.png

Same cloudy rainy day but inside:
1576042773983.png

Direct sunlight:
1576042657555.png
 

Garry H (Cut Nut)

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mission1

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Is there a difference on GIA certs between “medium” and “medium blue”, or is it the same thing stated differently? I tried searching for this a while ago but couldn’t find an answer.
 

OoohShiny

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Is there a difference on GIA certs between “medium” and “medium blue”, or is it the same thing stated differently? I tried searching for this a while ago but couldn’t find an answer.
With thanks to @ecf8503 for the picture :) 95% of diamonds with fluor have blue fluor:



so it is highly likely to be the same.

If it's not, and it's white or yellow or green... that is indeed a rare stone!

(Orange fluor may be indicative of a Man Made Diamond / Laboratory Grown Diamond, though, so caution is needed if buying an uncertified stone showing that property.)
 

Rockdiamond

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There’s a lot of pages here...what’s the best lighting to measure a K color with strong fluorescence? Cloudy day? Direct sun? Although, I’ve heard direct sun can make a great cut stone look not so great.
I read this differently- diamonds lR4eVR asked about “measuring”
I take it to mean accurately grade the body color.
That question does go to the heart of the matter.
I’d grade ( measure) the color using fluorescent lighting, combined with daylight.
GIA does not use daylight.
This is one reason fluorescent diamonds are so tough to grade accurately.
The word fluorescent has a lot of letters- so a lot of people just write Medium.
If GIA declares the fluorescence to be medium they will define the color.
 

sledge

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If indeed you are trying to measure/grade body color I am of a different opinion than @Rockdiamond.

I believe you want to grade a stone with fluor with as little UV/VV intensity as possible to neutralize any potential whitening effects.

The reasoning is simple and goes back to @Karl_K's statement earlier about your specific lighting environments. Depending how we live and function you will be exposed to an array of lighting conditions. Since most people are bothered by too much tint, I find it important to know the worst case scenario (aka "floor") for what the true color looks like.

If you can live with that floor then any potential whitening effects you gain are a bonus and only improves your feeling about the stone. All assuming you believe less color is better. If you prefer tint, you may have the opposite viewpoint.

Whereas, if you measure/grade as @Rockdiamond suggested you'd be introducing more UV/VV radiation which could theoretically cause the stone to fluorescence and alter the grade.

As far as color goes, blue is most common but not the only color. Also, you have to consider diamond body undertones. Many undertones are yellow, but you can also have grey, brown and other colors. What's confusing is GIA doesn't have to report certain body undertones until they reach a certain color grade.

This is important because blue fluor in combo with a yellow undertone may provide a whitening effect. However, other colors of fluor combined with various colors of fluor may create a different result.


original-GIA-Color-Grade-Boundries-for-Undertones-and-Fancy-Colors.jpg
 

Texas Leaguer

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Is there a difference on GIA certs between “medium” and “medium blue”, or is it the same thing stated differently? I tried searching for this a while ago but couldn’t find an answer.
Normally a GIA report will have the color of the fluourescence immediately after the strength when the strength is medium or greater (e.g medium blue or medium yellow). Otherwise it will say Faint or None.

Other labs report fluorescence differently.

Do you have a GIA report that just says Medium without a color designated?
 

mission1

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Normally a GIA report will have the color of the fluourescence immediately after the strength when the strength is medium or greater (e.g medium blue or medium yellow). Otherwise it will say Faint or None.

Other labs report fluorescence differently.

Do you have a GIA report that just says Medium without a color designated?
Actually it might just be an inventory inconsistency rather than GIA. See example below from Blue Nile
 

Attachments

diamondsR4eVR

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What is your goal? Meaning, are you trying to determine if a stone is hazy/cloudy because of the strong fluor? Or are you wanting to see if it turns a bluish hue? Or maybe if you are just wanting to see how it may whiten in optimal conditions? Or...or....or.

You get my point.

Depending what you are trying to achieve, the answers may vary. For instance, viewing a stone in direct sunlight will theoretically expose it to the most UV radiation which then cause the stone to fluorescence. In this condition, you could see that bluish hue. Also, if the fluor creates that hazy look, it would be most prevalent in this condition.

Even when viewing outside, you have to consider if it's direct sunlight or cloudy or the time of day, etc.

Have you seen this thread yet? I don't think you'd have the same result, but it shows what a very strong blue fluor in a D stone can change in various lighting conditions.


There are more pictures, but here are a few I thought you may find interesting.

Cloudy rainy day/indirect sunlight:
1576042714122.png

Same cloudy rainy day near window:
1576042923450.png

Same cloudy rainy day but inside:
1576042773983.png

Direct sunlight:
1576042657555.png
That’s a stunning stone! When I see stones like this in everyday situations it confirms, imho, that consumers overreact when it comes to fluorescence. That’s not to say the the bad ones do not exit. I had one many years ago that was gifted to me that was a J, milky and hazy stone. I hated it! But in hindsight, that probably had more to do with it’s cut and clarity than anything else.
 

Karl_K

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The key thing is that the lighting used to set the grade on the report and the the lighting you see the diamond under are 2 different things.
What is under debate is what lighting and how much UV is the right amount for lab grading.
When your looking at a diamond the lighting is what it is at that time and will make the diamond do different things depending on the number, type, intensity, and color of lighting and the cut of the stone. Rarely are consumers is a mono lighting situation, there is always more than one light source even if its a reflection of the primary source.
 

Texas Leaguer

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Actually it might just be an inventory inconsistency rather than GIA. See example below from Blue Nile
Yes, most likely their vendors are providing data in different formats. The vast majority will be blue, but you can click through to the actual lab report to confirm.
 

Rockdiamond

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@sledge - I’m curious as to how you’ve formed your opinions on how to grade the color of a diamond?
I have graded literally thousands of diamonds that did not have GIA reports. In many cases I have graded original productions ( while I was grading for a DeBeers Site Holder) so I estimated the grade prior to GIA submission. I earned a reputation as accurately predicting the GIA grades in a majority of stones.
That’s a small part of the experience which forms my ideas about how to color grade diamonds that I’m bringing to the discussion..
I’ll just have to say this- as he won’t respond- I don’t believe Bryan was or is a diamond buyer or grader.
That doesn’t invalidate his or your ideas- but for all those reading we need to put this in context.
 

Rockdiamond

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Actually it might just be an inventory inconsistency rather than GIA. See example below from Blue Nile
The lists stones you see on “Virtual “ diamond sites is drawn directly off two main data feeds- where the cutters list their diamonds. Some of the people doing the data entry skip the word Blue. They also sometimes skip other places where the person doing data entry can free enter
 
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