Is most color grading the grading of "TONE"?

[oldminer]

Let''''s consider ONLY grading the color of diamonds from D through M. There are several hues that are graded in the standard GIA scale which include Yellow, Brown Yellow, Brown, Geenish Yellow and all the slightly more mixed hues of these color types too.

Do gemologists feel that when they grade diamonds for which one of two is a lower color, they actually look to see which one is darker in TONE?......colorless (white) to black (more body color). Or, do some feel that they are still analyzing the Color and using human perception of depth of color to denote which stone is more colored?

I have an opinion developed over quite a bit of time, but wonder how others feel and if this train of thought might stimulate some good suggestions on how to make diamond color grading not only more objective, but also more of a "standard" and less of a system.

Thanks for your good input.

 

[Richard Sherwood]

Yes, I color grade by tone.

For example, a "K" color faint brown stone will have the same tone as a "K" color faint yellow stone, but the faint yellow body color will be more apparent to the eye. The tones are the same, but the yellow color is more apparent to the eye.

 

[strmrdr]

Rich im going to have to strongly disagree with you on this issue. :{

Your saying that grading by tone is a good thing?
tone does not matter, how visible it is too the human eye does.
nothing else matters.

If a yellow stone and a brown stone have the same tone and the yellow is more visible then the stone should get a lower grade.
Where did all the crazy ideas for grading come from?
This one and the relative inclusion size one are just plain stupid in my opinion.
This is why I think a iso standard is needed that is required by law to be followed.

grumpy storm

 

[Garry H (Cut Nut)]

Good question Dave.

Storm you got the cat by the wrong end mate! The end with sharp teeth.

Brownish shades tend to face up darker than cape yellowish, but cape is often more easily identified by consumers in shops as "off colored" - they see brownish TTLB''s often as greyish - the brown is not vivid.

That said - if an I is a low I and brownish I might call it J. It would not be until the diamond is maybe L brownish before I would call it ''brownish L'' on an appraisal.

But what do you do with a pinkish hue? We often found them in parcels from Argyle - and even though we specialize in pink diamonds I sent them back because they were not 1 thing or the other. They do not have an attractive hue like say a blueish stone. And they are all blue fluoro - which makes them look wierd and different colors in diff light.

 

[strmrdr]

Lets look at the most common use of color grade by consumers

Its used in 2 areas:
1: price
2: to compare 2 diamonds to see if they are "white" enough for them.

Tone does not serve the second case at all.
If someone goes into a store and sees that a GIA G is there cut off point on color they should be able to be confident that another GIA G will also be acceptable, grading by tone instead of visual shading does not work for consumers there.

Garry if im reading you right, 2 diamonds both the same tone one pink and one blue, you send the pink one back?
I think that makes my case for me.

 

[Garry H (Cut Nut)]

Yes Storm - we agree - hue is also important.
But you implied yellow was worse than brown - that is our only disagreement

 

[pyramid]

strmrdr

I didn''t realise you were a gemmologist. Surely Richard knows what he is talking about.

 

[Richard Sherwood]

Hey, I''ve got Pyramid in my corner. Watch out or we''ll kick ass and take numbers.

Storm, that''s the standard for color grading. The way I was taught by GIA.

You have several different body colors, but most commonly yellow, brown or grey. They each have different visual appearances, but the color grade is determined by the tone of the individual color.

Most consumers will recognize a yellow "K" easier than a brown or grey "K", but that doesn''t change the fact that all three would have the same depth or "tone" of color.

It''s part of the nuance of color grading and color appreciation. I personally prefer a faint brown "K" over a faint yellow "K", but many dealers prefer the faint yellow.

If you started assigning color grades differently based on the body color instead of tone it would be a mess. Better to grade them all equally based on tone, and then assign whatever personal handicap system you prefer. Add all those personal preferences up and the market will eventually sort it out with a trend in one direction or another.

 

[strmrdr]

Date: 3/30/2006 1:29:18 AM
Author: Pyramid
strmrdr


I didn't realise you were a gemmologist. Surely Richard knows what he is talking about.

Im not ... yet.....
I know he knows what he is talking about and 99% of the time I agree with him but on this one I don't even get where he is coming from on it.
In storm terms it does not compute.

edit:
woops see he came in and explained it while I was posting this....
will read then respond....

 

[strmrdr]

Date: 3/30/2006 1:57:21 AM
Author: Richard Sherwood
Better to grade them all equally based on tone, and then assign whatever personal handicap system you prefer. Add all those personal preferences up and the market will eventually sort it out with a trend in one direction or another.

I see where your coming from but....
That works for the trade but does it work for consumers?
Consumers want accurate, repeatable, consistant and relevant grading to help in the buying decision.
Visible coloring is a lot more relevant than tone?
tone + handicap type system thats an universal standard would work but I just dont see tone alone being good for consumers.
Like a lot of things in the trade its another thing I think needs improvement.

 

[Richard Sherwood]

I can''t wait for you to get in the trade and start changing things, Storm. Things have been a bit dull lately.

 

[f0rbidden]

I guess I''m wondering now, after reading this - I know there are tools used by gemologists to grade color - or lack thereof - in diamonds.

so is there not a set ''key'' so to speak, that says THIS is what a G is, or THIS is what an L is that would - across the board - always be the same as a baseline?

Are color gradings always subjective?

 

[MissAva]

There are master diamond sets, and though I am less okay with them, master CZ sets aw well to compare color there are machines called spectrophotometer (sp?) which are supposed to be super accurate at grading color but I do not know as much about them. I would trust a good appraiser and the grading labs. AGS and GIA and independent appraisers spend their life looking at diamonds and learning all the little subtle nuances of tone, shade, color, really it is quite amazing when you think about it.
I would like to see a standard across the board for color, but I don’t think it is likely in the near future.
Oh and I like gray tinted things it gives them a romance to me.

 

[oldminer]

Years ago, I sent a diamond that had many fine black inclusions inside it to my fellow gemologist, Tom Tashey, now owner of PGS labs in Chicago. He is one of those dedicated gemologists that you simply can trust. I needed his advice and experience.

The diamond was a very pure, colorless body color EXCEPT that the fine black inclusions made the stone appear DARK, about J/K range when color graded by TONE. It was it D-E-F in range if one neglected the effect of the inclusions, and it was not brown or yellow. Since I had no master stones like it, I wanted a different and respected opinion.

Tom graded it J, if I recall. He told me it was the lab policy to grade it by the darkness, the tone, when no masters of that hue existed...... Other members of the trade, such as diamond dealers, admit this is a correct strategy. However, for those on a tight budget, a grey tone stone may look nicer than an equally yellow or brown one. It is a matter of personal taste and comparision. Many dark stones are sold as if they were far better in color. If a customer doesn''t know better, they can be fooled. Lots of jewelers don''t know better. It isn''t just consumers.

I know the CIE color coordinates of diamonds can be measured. These can be converted to Hue, Saturation and Tone. Maybe we can use tone to grade depth of mixed colors and maybe not. I don'';t yet have details on human perception of tone accross various hues...... I am looking.

 

[WinkHPD]

Date: 3/30/2006 2:10:34 AM
Author: strmrdr

Date: 3/30/2006 1:57:21 AM
Author: Richard Sherwood
Better to grade them all equally based on tone, and then assign whatever personal handicap system you prefer. Add all those personal preferences up and the market will eventually sort it out with a trend in one direction or another.

I see where your coming from but....
That works for the trade but does it work for consumers?
Consumers want accurate, repeatable, consistant and relevant grading to help in the buying decision.
Visible coloring is a lot more relevant than tone?
tone + handicap type system thats an universal standard would work but I just dont see tone alone being good for consumers.
Like a lot of things in the trade its another thing I think needs improvement.

Not sure I like the personal handicap system. GIA taught when I was in school, you know, back in the dark ages, that you graded the tone of the color, not the color itself. Remember, we are talking about incredibly pale coloring that is not noticeable by many once the stones are set and viewed face up, especially in the H-I coloring and higher.

The top light browns and top top light browns are examples of this. The browns face up whiter but sell for less at the wholesale level than a comperable yellow and much of the (expletives deleted) that you see at the mall in 2 ct tennis bracelets for $499 is tlb or ttlb I2 - I3 frozen spit that might look even worse if it were the same color of yellow body color. At this level of ugliness, the clarity is of more impact than the color.

The market place has an incredible ability to value things properly in the long run, so I have to dissagree with you Storm that the consumer is in any way harmed by a gemologist doing the job as he was trained to do and as all of his colleagues were trained to do. If we all grade the stones the same then the consumers all get the same information.

Of course we do not all grade the same, which is why the consumer is better served in most instances by getting a recognized diamond report and getting the report that gives him/her the information that is desired. You probably still prefer the AGS paper for the quality of the information given, but for most the GIA paper will be sufficient. If not, the market will quickly vote with its feet to the paper that is needed. Me, I hope it is the AGS paper until GIA changes their system somewhat, but time will tell.

Wink

 

[oldminer]

Please guys, let''s keep the postings on this thread to the topic as much as possible. THANKS.

 

[Garry H (Cut Nut)]

You sucked me dry already dave!!

 

[Richard Sherwood]

Date: 3/30/2006 1:22:57 PM
Author: Wink

Not sure I like the personal handicap system. GIA taught when I was in school, you know, back in the dark ages, that you graded the tone of the color, not the color itself.

Yes, we are in agreement Wink. The "personal handicap system" I''m talking about is the preference or non-preference that dealers/consumers have about different hues, and the pricing discount or premium they would personally assign based on their preference.

 

[WinkHPD]

Gotvha!

I am reminded of the fact that there are color blind diamond graders who can grade diamonds very well from D down to at least LMNOP. They must be grading on tone since they sure as heck can not see the hue...

Wink

 

[Garry H (Cut Nut)]

I heard chocolate can be good for making you color blind too (

and too much

does something?)

Dave and Storm - for Imagem and Storm''s assistance I guess you would both prefer a system that assessed the face up color?

Many ideal cut people would say the same thing - better cut stones look lower in color.
i know nice princess in H color look like I J rounds.

so maybe there is a better way?

 

[denverappraiser]

Color, as defined by GIA for describing 'colorless' diamonds, is a measure of tone as viewed diagonally from the back and under a reasonably well defined lighting environment. People who are wishing to describe the color of other things will include elements of hue and saturation and it’s clear that diamonds could be measured in these ways if there was some compelling reason to do so. I think we all agree that the hue of a stone has a significant affect on the look, the desirability and the expected price. This sort of thing can become a self-fulfilling prophecy and it becomes difficult to separate genuine consumer preference from consumers wishing to have a stone that gets a better score on a widely recognized scale. It also has an affect on the accuracy of the grading. Comparing yellow masters with a pink subject stone for tone only is decidedly difficult and can compound the difficulty of applying an already difficult system. As counterintuitive as it seems, it would probably help to be color blind when grading diamond color.

Is there a better way? Probably, but it depends on what you’re trying to describe and what constitutes an improvement in the system. Shining a laser into a stone and observing how the returned light has been changed could tell you quite a bit about the color of the stone, especially if you chose a laser where you could adjust the incoming light so you make a variety of observations over a large spectrum of available light. Whether this could then be distilled into a scoring system that reasonably reflects what people seem to value strikes me as a bit of a leap and the added complexity of using this sort of equipment, although perhaps scientifically more repeatable, and I'm not convinced that it would benefit anyone but the labs.

Neil Beaty
GG(GIA) ISA NAJA
Professional Appraisals in Denver

 

[strmrdr]

Neil hit on something that Iv been thinking about...
Diamond grading is based on primative tools.
basicaly a 10x loop and a master set and a couple guages.
cut measurement is finaly being brought into modern times isnt it time for the rest of the C''s to be?

Garry and everyone,
Id like to see a face up color system explored if for nothing else the teaching value.
Has a study been done of face up color vs traditional color grading?
There is a lot of talk about it and a lot of hype from some corners on it but is there an actualy scientific study that has been done on it?

 

[MissAva]

Correct me if I am wrong, but I thought the tint within the stone came from the type and amount of gas present when the stone was forming. Is there a way to measure that gas, something like carbon 14 dating, with out harming the stone?

 

[Rhino]

Hi Dave,

I''ve ran across these kinds of stones as well where body color appeared colorless yet due to the amount of darkness caused by the speckles, never felt comfortable assigning it a colorless grade. These would generally be stones we saw or acquired through estates.

 

[Rhino]

Date: 3/31/2006 9:05:42 AM
Author: Matatora

Correct me if I am wrong, but I thought the tint within the stone came from the type and amount of gas present when the stone was forming. Is there a way to measure that gas, something like carbon 14 dating, with out harming the stone?

Hi Mata,

If memory serves me right the yellow color is caused from traces of nitrogen as the carbon is crystalizing. Various colorimeters on the market can measure the amount of hue within a gemstone like the SAS2000 which Rich has, the Gran Colorimeter, and I think the Imagem has a color measuring device as well.

It''d be interesting to see how one of those speckled inclusion diamonds would rate on it. That might be an instance that may fool the technologies and be more reliant on human testing and comparison.

Peace,

 

[pricescope]

Date: 3/31/2006 9:05:42 AM
Author: Matatora

Correct me if I am wrong, but I thought the tint within the stone came from the type and amount of gas present when the stone was forming. Is there a way to measure that gas, something like carbon 14 dating, with out harming the stone?

Hey Mat, carbon 14 dating is only used for organic materials which diamonds are not. Shortly, because this method is based on ratio between carbon14 and carbon12 presented in biological object upon it's death which used as a referral point for further calculations.

So even though diamonds are to "die for'

, carbon 14 dating requires actual death long time ago to work on.

will not bet more than 2 cents on my story though

 

[jasontb]

Date: 3/31/2006 8:41:05 AM
Author: strmrdr
Id like to see a face up color system explored if for nothing else the teaching value.

Has a study been done of face up color vs traditional color grading?

There is a lot of talk about it and a lot of hype from some corners on it but is there an actualy scientific study that has been done on it?

IMHO, that''s not a great idea. If a stone is an H it''s an H. Seems silly to say, ''It''s an H but if you look at it this way it looks like an E.'' If you like and H because you can''t see the difference in color face up, then that''s cool. But to have the diamond graded that way...seems...wrong. Plus, how are you going to determine what color a diamond faces up like? Just seems unscientific? I want to know what I''m buying, not what it looks like I am buying.

 

[oldminer]

Fancy color diamonds ARE graded as they face up. Many of them would fail to be fancy color when graded like near colorless diamonds. I guess we know who is in charge of how things are done in the big labs. Anything to favor sellers and higher value is generally part of the process. I don't say it is faulty, but it is something few people consider or understand. The process can be made more objective, but will dealers and large sellers accept such large changes in the value equation. It won't be an easy thing to change so many years of very traditional business practices.

Another element to consider is that the larger the diamond, the darker it gets. Light is absorbed. The system in use today makes a mental adjustment. A machine must have a complex program to do a similar thing.

 

[valeria101]

Date: 3/31/2006 3:13:34 PM
Author: jasontb

But to have the diamond graded that way (face up)...seems...wrong.

... these are the only precious stones whose color is evaluated anything but face up. Since I feel that these goods are only as good as they look (what else are they good for?)... ''guess I''d rather disagree. Not that this matters - it isn''t like there is no relation between face up & face down color or that as is apparent color has no say in the grades (referring to the way fancy shapes are color graded).

2C

Anyway, does it even matter? Any new grading system will have to make a value added proposition, regardless of anything else. When all is said and done, I wonder if any one technical approach truly holds its ground above all others. At least the current discussion seems to dwell on rather fine detail rather than a radical new way of doing things. With reasonably well established authority in place, I wonder if incremental change (i.e. telling grays from browns in near colorless range or splitting the D grade... or such) is not harder to bring about than a something quite a bit more radical.

 

[MissAva]

Date: 3/31/2006 1:13:47 PM
Author: Pricescope

Date: 3/31/2006 9:05:42 AM
Author: Matatora

Correct me if I am wrong, but I thought the tint within the stone came from the type and amount of gas present when the stone was forming. Is there a way to measure that gas, something like carbon 14 dating, with out harming the stone?

Hey Mat, carbon 14 dating is only used for organic materials which diamonds are not. Shortly, because this method is based on ratio between carbon14 and carbon12 presented in biological object upon it''s death which used as a referral point for further calculations.

So even though diamonds are to ''die for''

, carbon 14 dating requires actual death long time ago to work on.

will not bet more than 2 cents on my story though

I''m what I meant was the same sort of technology to scan for the diffrent gases. John said that had something like that now, if it is 98% or so effective why not make it the standard?