GIA misgrading stones with strong fluor?

[angeline]

Hi all,

I have read a few older threads that suggested that when GIA grade stones for color the environmental lighting they use contains UV and therefore the color could be misgraded higher in a stone that has fluorescence because of the color-heightening effect of fluorescence.

Is this true? false? kind of, maybe a bit true?

Thanks for any input!

a

 

[oldminer]

GIA grades in the lighting environment they choose to use. SInce they use their own system, the lighting environment is most likely the corect one and their grades meet with their system. They would say they grade diamonds correctly. There are other schools of thought on what is or is not proper lighting environments for color grading. If a lab speicifes what environment it uses and if that environment is different than the GIA, then one would expect some fluorescent effects would make the apparent body color differ.

Basically the trade prefers to put a postivie, value adding, spin to diamond grades within the scope of an acceptable system. GIA has a pretty good balance in the system in use. It does have some UV present.

 

[stebbo]

Date: 9/16/2007 5:45:58 PM
Author:angeline
Hi all,

I have read a few older threads that suggested that when GIA grade stones for color the environmental lighting they use contains UV and therefore the color could be misgraded higher in a stone that has fluorescence because of the color-heightening effect of fluorescence.

Is this true? false? kind of, maybe a bit true?

Thanks for any input!

a

The color-heightening effect of fluoresence we will notice is primarily dependent upon:

1. the level of UV in the lighting environment we visit (stength and distribution)
2. the amount of color in the diamond to start with (E or K?)
3. how complimentary (or cancelling) the fluoresce color is to the diamond color, for example:
   
   • is the diamond more yellowish or brownish?
   • what wavelength blue does the diamond fluoresce? What about (rare but color-worsening) orange/yellow fluorescence?

The average consumer simply wants to know how much tint they will roughly see and can't be expected to take all the above into consideration. The GIA/EGL-type non-filtered grading environment attempts to help the consumer out here. I don't see it as misgrading.

 

[angeline]

Okay, thanks for the input.

My question comes from the position of being interested in a GIA graded E with strong fluor. I would just hate to pay for an E that without fluor was really a G.

If the effect of the fluor was all-pervasive then of course I wouldn''t complain. If my everyday viewing environment is without any UV and I see a G most of the time, then I wouldn''t be happy.

I guess I would prefer a grading system that was base-line no UV present. After all GIA can''t tell how much UV is in my normal viewing environment.

Thanks for the replies...

a

 

[Richard Sherwood]

I use the SAS2000 spectrophotometer developed by Marty Haske (a strong GIA critic) as a second opinion on my color grading. The SAS is extremely objective, and has a UV filter which enables color grading with and without UV influence. It's interesting to see the results with and without the filter.

Usually I notice a one grade improvement in color with strong blue fluorescence, and a quarter to half grade improvement with medium blue fluorescence. Most the times the GIA seems to still grade in correlation with the SAS's non-UV baseline grading. A minority of times no, but most the time yes.

Worst case scenario is that you have an F which improves to an E in some lighting (usually indirect daylight). In that case the discount applied to colorless stones with strong blue fluorescence (7-10% for IF-VVS, and 3-5% on VS) would usually compensate for this while the best case scenario is that you're getting an E color diamond which looks like a D at at times.

 

[Garry H (Cut Nut)]

Date: 9/16/2007 9:37:18 PM
Author: Richard Sherwood
I use the SAS2000 spectrophotometer developed by Marty Haske (a strong GIA critic) as a second opinion on my color grading. The SAS is extremely objective, and has a UV filter which enables color grading with and without UV influence. It''s interesting to see the results with and without the filter.

Usually I notice a one grade improvement in color with strong blue fluorescence, and a quarter to half grade improvement with medium blue fluorescence. Most the times the GIA seems to still grade in correlation with the SAS''s non-UV baseline grading. A minority of times no, but most the time yes.

Worst case scenario is that you have an F which improves to an E in some lighting (usually indirect daylight). In that case the discount applied to colorless stones with strong blue fluorescence (7-10% for IF-VVS, and 3-5% on VS) would usually compensate for this while the best case scenario is that you''re getting an E color diamond which looks like a D at at times.

Thanks Rich.
Thanks for the info, and clarifying analytically the amount of deiation.

Thanks to Dave also for taking the heat out of the situation.

Of course unlesss the diamonds is over 5ct you would never be able to pick an F from a E anyway.
And as Rich says, the idea that you will have a free D in some lighting is an extra bonus. I love Blue White diamonds.

 

[angeline]

Well Rich, I was thinking that getting it appraised in that manner might put my mind at rest.. I''ll see what the IS, Sarin etc look like then maybe see about checking it out further...

Thanks,

a

p.s. Garry... I like the idea of a free D... I just don''t ike the idea of an expensive F, LOL!

 

[Garry H (Cut Nut)]

Date: 9/16/2007 10:57:33 PM
Author: angeline
Well Rich, I was thinking that getting it appraised in that manner might put my mind at rest.. I''ll see what the IS, Sarin etc look like then maybe see about checking it out further...

Thanks,

a

p.s. Garry... I like the idea of a free D... I just don''t ike the idea of an expensive F, LOL!

i expect it is a little like an F price because of the fluoro - which makes it a steal!!!

 

[Fly Girl]

Great question, Angeline, and thank you so much for the quantitative answer, Rich. I was looking at a 1.7 ct G with strong blue fluor and a GIA certificate earlier this year, and I was bothered by the same question. I wanted that G to look better with UV present, not to have the effects of that already built in and have it look like an H without UV present. Guess this is another reason to have an appraiser with the right equipment take a look.

 

[stebbo]

Date: 9/16/2007 9:37:18 PM
Author: Richard Sherwood

Usually I notice a one grade improvement in color with strong blue fluorescence, and a quarter to half grade improvement with medium blue fluorescence. Most the times the GIA seems to still grade in correlation with the SAS''s non-UV baseline grading. A minority of times no, but most the time yes.

Are you saying here Richard that the SAS2000 (in non-UV mode) matches the GIA most of the time for strong fluor stones, or most of the time because only the occasional stone has strong or greater fluorescence or greater to cause a difference?

 

[Richard Sherwood]

Date: 9/16/2007 11:29:02 PM
Author: stebbo

Date: 9/16/2007 9:37:18 PM

Author: Richard Sherwood

Usually I notice a one grade improvement in color with strong blue fluorescence, and a quarter to half grade improvement with medium blue fluorescence. Most the times the GIA seems to still grade in correlation with the SAS's non-UV baseline grading. A minority of times no, but most the time yes.

Are you saying here Richard that the SAS2000 (in non-UV mode) matches the GIA most of the time for strong fluor stones, or most of the time because only the occasional stone has strong or greater fluorescence or greater to cause a difference?

I'm saying the majority of time it is a match on stones with strong blue fluorescence, and a minority of times it is not.

Very strong blue stones can have a color improvement of up to two grades over their non-UV grade. I can't really give you a feel for how those stones correlate with their GIA reports, as I don't see many "very strong blue" GIA certed stones.

It's interesting also to see how yellow fluorescence will affect UV and non-UV grading. Same basic results, only in the opposite direction.

 

[angeline]

Date: 9/16/2007 9:37:18 PM
Author: Richard Sherwood
I use the SAS2000 spectrophotometer developed by Marty Haske (a strong GIA critic) as a second opinion on my color grading. The SAS is extremely objective, and has a UV filter which enables color grading with and without UV influence. It's interesting to see the results with and without the filter.


Usually I notice a one grade improvement in color with strong blue fluorescence, and a quarter to half grade improvement with medium blue fluorescence. Most the times the GIA seems to still grade in correlation with the SAS's non-UV baseline grading. A minority of times no, but most the time yes.


Worst case scenario is that you have an F which improves to an E in some lighting (usually indirect daylight). In that case the discount applied to colorless stones with strong blue fluorescence (7-10% for IF-VVS, and 3-5% on VS) would usually compensate for this while the best case scenario is that you're getting an E color diamond which looks like a D at at times.

Oh Rich, I just re-read your answer. I thought you were saying that you saw a one grade improvement in the color grading that is reported on the certificate, but then I read more and you say that GIA is in agreement with your non-UV assessment.

Am I reading you correctly in summary:

1. Strong fluor improves color grade by approx 1 grade.

2. GIA reports the lower non-UV influenced color grade most of the time.

Thanks!

a

 

[stebbo]

Date: 9/16/2007 11:50:20 PM
Author: Richard Sherwood

I''m saying the majority of time it is a match on stones with strong blue fluorescence, and a minority of times it is not.

That''s very interesting. As you usually notice a 1 grade diff between the SAS2000''s UV and non-UV modes, yet the non-UV mode matches GIA the majority of the time, then that suggests to me that the GIA''s daylight UV intensity is indeed very weak, closer matching the SAS2000''s non-UV environment than it''s UV enviroment.

It would also explain why Rhino finds good correlation with his Gran DC3000, it having only weak UV lighting.

 

[angeline]

Date: 9/17/2007 12:22:15 AM
Author: stebbo

Date: 9/16/2007 11:50:20 PM

Author: Richard Sherwood


I''m saying the majority of time it is a match on stones with strong blue fluorescence, and a minority of times it is not.

That''s very interesting. As you usually notice a 1 grade diff between the SAS2000''s UV and non-UV modes, yet the non-UV mode matches GIA the majority of the time, then that suggests to me that the GIA''s daylight UV intensity is indeed very weak, closer matching the SAS2000''s non-UV environment than it''s UV enviroment.


It would also explain why Rhino finds good correlation with his Gran DC3000, it having only weak UV lighting.

This seems all good news to me!

a

 

[stebbo]

Date: 9/17/2007 12:18:53 AM
Author: angeline


Oh Rich, I just re-read your answer. I thought you were saying that you saw a one grade improvement in the color grading that is reported on the certificate, but then I read more and you say that GIA is in agreement with your non-UV assessment.

Am I reading you correctly in summary:

1. Strong fluor improves color grade by approx 1 grade.

2. GIA reports the lower non-UV influenced color grade most of the time.

Thanks!

a

Yes that confused me too Angeline - Rich did mention that the 1 grade difference was between the two UV modes on his colorimeter, but said the GIA matches the non-UV mode, hence my conclusion above.

 

[stebbo]

Date: 9/17/2007 12:26:43 AM
Author: angeline

Date: 9/17/2007 12:22:15 AM
Author: stebbo

Date: 9/16/2007 11:50:20 PM

Author: Richard Sherwood


I'm saying the majority of time it is a match on stones with strong blue fluorescence, and a minority of times it is not.

That's very interesting. As you usually notice a 1 grade diff between the SAS2000's UV and non-UV modes, yet the non-UV mode matches GIA the majority of the time, then that suggests to me that the GIA's daylight UV intensity is indeed very weak, closer matching the SAS2000's non-UV environment than it's UV enviroment.


It would also explain why Rhino finds good correlation with his Gran DC3000, it having only weak UV lighting.

This seems all good news to me!

a

I just don't know if it's true or not, and I possibly suspect not!

It's however the only conclusion I'm coming too.

 

[angeline]

Date: 9/17/2007 12:28:28 AM
Author: stebbo

Date: 9/17/2007 12:26:43 AM

Author: angeline

Date: 9/17/2007 12:22:15 AM

Author: stebbo

Date: 9/16/2007 11:50:20 PM


Author: Richard Sherwood



I''m saying the majority of time it is a match on stones with strong blue fluorescence, and a minority of times it is not.

That''s very interesting. As you usually notice a 1 grade diff between the SAS2000''s UV and non-UV modes, yet the non-UV mode matches GIA the majority of the time, then that suggests to me that the GIA''s daylight UV intensity is indeed very weak, closer matching the SAS2000''s non-UV environment than it''s UV enviroment.



It would also explain why Rhino finds good correlation with his Gran DC3000, it having only weak UV lighting.

This seems all good news to me!

a

I just don''t know if it''s true or not, and I possibly suspect not!


It''s however the only conclusion I''m coming too.

Given Rich''s experience it is the only logical conclusion.

 

[stebbo]

Date: 9/17/2007 12:35:25 AM
Author: angeline

Date: 9/17/2007 12:28:28 AM
Author: stebbo


I just don't know if it's true or not, and I possibly suspect not!


It's however the only conclusion I'm coming too.

Given Rich's experience it is the only logical conclusion.

Rich's observations = trustworthy, my conclusion explaining them = suspect is what I was trying to say here. There could be another explanation.

 

[angeline]

Date: 9/17/2007 1:09:08 AM
Author: stebbo

Date: 9/17/2007 12:35:25 AM

Author: angeline

Date: 9/17/2007 12:28:28 AM

Author: stebbo



I just don''t know if it''s true or not, and I possibly suspect not!



It''s however the only conclusion I''m coming too.

Given Rich''s experience it is the only logical conclusion.

Rich''s observations = trustworthy, my conclusion explaining them = suspect is what I was trying to say here. There could be another explanation.

Do you have any theories on what that might be? I''m interested.

a

 

[oldminer]

I also have an SAS2000 from Matry and it does exactly what Rich has indicated. I find it useful, but because it does grade differently than the GIA in the UV blocked mode, I rarely want to use it that way except to prove a point with someone about why lighting has an effect on color grading. For some reason(s) the SAS2000 does not grade all color like the GIA does. I think that as diamonds get larger, the grading system adjusts while the machine grades what is there on the device. An E color 6 carat diamond looks like an F/G color diamond because of absorption. The human eye and brain makes this adjustment where a device without programming to make this leap won''t.

 

[stebbo]

Date: 9/17/2007 7:18:39 AM
Author: oldminer
I also have an SAS2000 from Matry and it does exactly what Rich has indicated. I find it useful, but because it does grade differently than the GIA in the UV blocked mode, I rarely want to use it that way except to prove a point with someone about why lighting has an effect on color grading.

Ok Dave, you've really confused me now. Rich said "most the times the GIA seems to still grade in correlation with the SAS's non-UV baseline grading" and you're saying yours does what Rich's does, yet yours grades differently?

I'll think I'll take the dog for a walk, let this red wine wear off...

 

[strmrdr]

Date: 9/17/2007 7:50:12 AM
Author: stebbo

Date: 9/17/2007 7:18:39 AM
Author: oldminer
I also have an SAS2000 from Matry and it does exactly what Rich has indicated. I find it useful, but because it does grade differently than the GIA in the UV blocked mode, I rarely want to use it that way except to prove a point with someone about why lighting has an effect on color grading.

Ok Dave, you've really confused me now. Rich said 'most the times the GIA seems to still grade in correlation with the SAS's non-UV baseline grading' and you're saying yours does what Rich's does, yet yours grades differently?

I'll think I'll take the dog for a walk, let this red wine wear off...

All the labs apply a bogus fudge factor on large stones and the SAS doesn't.
ie a G 1ct is not the same color as a G 4ct.
The material is supposedly near the same color but the 4ct has more of it so the light picks up more tint.

 

[stebbo]

Date: 9/17/2007 1:26:31 AM
Author: angeline

Date: 9/17/2007 1:09:08 AM
Author: stebbo


Rich's observations = trustworthy, my conclusion explaining them = suspect is what I was trying to say here. There could be another explanation.

Do you have any theories on what that might be? I'm interested.

a

Nope - just respecting that there's a lot I don't know.

I've heard that experienced graders have an accuracy of +/- 0.5 of a color grade. The latest Gran has a similar accuracy. I like Marty's methods in his SAS2000, but don't know how accurate it is in correlating scientific color with human perception. I've also heard that the GIA uses multiple graders on color and a majority vote taken. Dave notes the irregulaties that creep in with larger diamonds and I believe it would a freak of nature if fluorescence affected a K color by the same amount as an E.

And then we have the GIA using UV light on the principle (or excuse) of everywhere we go has UV--but there's a big difference between the small amount of UV in tungsten, halogen and flourescent lighting to daylight, and there's a huge difference depending on the time of the day, weather, and location.

So what I'm saying is there are so many variables that I think I'll just buy a colored diamond next time.

 

[stebbo]

Date: 9/17/2007 8:10:11 AM
Author: strmrdr

Date: 9/17/2007 7:50:12 AM
Author: stebbo

Date: 9/17/2007 7:18:39 AM
Author: oldminer
I also have an SAS2000 from Matry and it does exactly what Rich has indicated. I find it useful, but because it does grade differently than the GIA in the UV blocked mode, I rarely want to use it that way except to prove a point with someone about why lighting has an effect on color grading.

Ok Dave, you''ve really confused me now. Rich said ''most the times the GIA seems to still grade in correlation with the SAS''s non-UV baseline grading'' and you''re saying yours does what Rich''s does, yet yours grades differently?

I''ll think I''ll take the dog for a walk, let this red wine wear off...

All the labs apply a bogus fudge factor on large stones and the SAS doesn''t.
ie a G 1ct is not the same color as a G 4ct.
The material is supposedly near the same color but the 4ct has more of it so the light picks up more tint.

Dave brought size up as a side issue--it didn''t sound to me like that''s the cause of the differing observations (although totally feasible). Feels more like a typing error at this stage.

 

[Richard Sherwood]

Yes, Stebbo & Angeline, you are understanding my statement correctly.

The GIA's grading is usually in line with the SAS's grading with the ultraviolet light filtered out, and then any improvement from color due to the fluorescent "kick" is above and beyond that, which also leads me to believe that the amount of UV in GIA's grading lamps must be minimal.

Apparently this is not the case with all labs though. For example, I appraised an interesting three+ carat pearshape with an EGL-Antwerp report a while back. They graded it as a "G" color with "slight luminescence", while I graded it as an "I" color with "very strong blue fluorescence". The diamond was absolutely gorgeous, and the interesting thing was that the selling vendor had it priced appropriately at the "I" color price range (which is nowhere near the "G" color price range). So the buyer ended up buying at an "I" price level but enjoying the benefit of the fluorescence "kicking" the color grade two shades whiter in some lighting.

Here is an excerpt from my critique_consultation regarding the stone:

This is an interesting diamond when it comes to color. In non-ultraviolet light (non-sunlight), it is a mid-level “I” color. Then, when brought anywhere close to daylight, the body color improves because of the very strong blue fluorescence reacting to the ultraviolet rays in the daylight. And it does this without any of the dreaded “oilyness” or “milkyness” which occurs in less than 5 percent of very strong blue fluorescent stones. Indeed, the slight to moderate blue overtone picked up in daylight has a very pleasing appearance, in this appraiser’s opinion.

So in other words, the fluorescence is a good thing. Indeed the Rapaport assigns up to a 3 percent premium on “I” color stones with strong blue fluorescence, depending on the degree that the fluorescence improves the body color of the diamond.

This diamond has a measurable improvement of up to two grades better color. The advanced colorimetry SAS-2000 spectrophotometer measures the increase as going from a mid-level “I” (2.79 on the 2.50-2.99 I range) to a mid-level “G” (1.76 on the 1.50-1.99 G range).

Neither of these grades are a “borderline” grade, but both “solid” grades smack in the middle of their respective scales. This was confirmed both by visual comparison to master diamond grading stones as well as analysis through the SAS-2000.

 

[Richard Sherwood]

If you're interested, I have a photo of what EGL-Antwerp regards as "slight luminescence", along with photos of the diamond showing the base body color and then the improved color with the fluorescent kick.

I can't figure out how to upload them though, as they are about 300kb while you can only upload to 100kb on the site here. If anybody would like to resize and post them for me I'd be happy to email them to you. It's a pretty good example of how fluorescence can be a desirable thing.

 

[angeline]

I''m very interested in the pics Richard. Alas I don''t think I am your best bet for jiggin pics around to post them

Anyone else? anyone, anyone?

 

[oldminer]

Richard, send them to [email protected]. I''ll make them smaller and load them for you.

 

[Richard Sherwood]

Thanks Dave!

 

[adamasgem]

Date: 9/16/2007 6:30:13 PM
Author: oldminer
GIA grades in the lighting environment they choose to use. SInce they use their own system, the lighting environment is most likely the corect one and their grades meet with their system. They would say they grade diamonds correctly. There are other schools of thought on what is or is not proper lighting environments for color grading. If a lab speicifes what environment it uses and if that environment is different than the GIA, then one would expect some fluorescent effects would make the apparent body color differ.

Basically the trade prefers to put a postivie, value adding, spin to diamond grades within the scope of an acceptable system. GIA has a pretty good balance in the system in use. It does have some UV present.

That goes to the issue, is it a "new D" or a "True D" and the age old standard that GIA once taught that "diamonds should be graded in artificial light, devoid of ultraviolet".

see "Is your G a J"

No surprise in them pandering to the trade (Certifigate or otherwise), and damn the consumer. It is not a "pretty good balance" as you say, but a continual one sided degradation in "standards".