Laboratory Master set photo

[30yearsofdiamonds]

Here is a photo of a Master Set used in the lab for color grading. The set goes from E to N. It's an ok photo but shows PSers how close colors are when deciding between 2 color grades.

 

[diamondseeker2006]

Very nice, thank you!

 

[Diamond_Hawk]

Nice demonstration. If these are top EX or ideal cuts, is it possible to line them in a tray, face-up, for another photo under the same lighting? It would be nice to see the face-up appearance versus table-down.

 

[emmebee]

This is very helpful, thanks!

 

[teobdl]

Here is a photo of a Master Set used in the lab for color grading. The set goes from E to N. It's an ok photo but shows PSers how close colors are when deciding between 2 color grades.

From this angle, it looks like I to J seems to be where tint turns from subtle yellow tint to more noticeable yellow. That seems to be my experience in real life, as well. Anyone else have thoughts on this?

Nice demonstration. If these are top EX or ideal cuts, is it possible to line them in a tray, face-up, for another photo under the same lighting? It would be nice to see the face-up appearance versus table-down.

Perhaps an even more helpful photo would be at 45 degrees from the table. This would probably be closest to the real-life look.

 

[Rockdiamond]

Nice shot Dan!

 

[ame]

Great shot, I second the request for a "45 degree" top down shot.

 

[teobdl]

Do these master diamonds represent the 50% mark of a color grade?

For example


<......D master.....>|<.....E master.....>|<......F master......>|<.....G master..... etc.

It would seem to be less subjective if instead they graded using a master maximal color diamond.

For example

<........ D master maximum>|<..........E master maximum>|<.......... F master maximum>|<..........G master minimum>| etc

That way, anything showing MORE color than the master maximum diamond is automatically bumped into the lower color grade.

 

[Diamond_Hawk]

Perhaps an even more helpful photo would be at 45 degrees from the table. This would probably be closest to the real-life look.

That's fine, although reflection of the camera lens will be more scattered around the diamond that way. I suppose one would have to take individual photos of each diamond to get the "usual" contrast pattern PS users are accustomed to, so 45 sounds good.

Do these master diamonds represent the 50% mark of a color grade?

Master stones represent the highest point in their respective grade range. So a diamond with less color than the master is a higher grade. That is why 30yearsofdiamonds does not need a D master.

 

[30yearsofdiamonds]

Diamondhawk is right on, and that goes for each master stone at the highest of its color.

 

[Karl_K]

If you don't mind I have had some questions for a long time and never a chance to ask someone who would know for sure.
How often does GIA acid clean their master sets?
Are they ever rechecked once they are released for use on the grading floor?
How long does a master set last before it has to be replaced?
Does each grader have an assigned set or do they just sign one out for the day?

 

[Gypsy]

Here is a photo of a Master Set used in the lab for color grading. The set goes from E to N. It's an ok photo but shows PSers how close colors are when deciding between 2 color grades.

Oh I love this. Thanks for posting. Wish the pic uploaded bigger. Can you crop it and maybe get the stones bigger? Then I could re-post!

 

[arkieb1]

 

[arkieb1]

Here is a photo of a Master Set used in the lab for color grading. The set goes from E to N. It's an ok photo but shows PSers how close colors are when deciding between 2 color grades.

Oh I love this. Thanks for posting. Wish the pic uploaded bigger. Can you crop it and maybe get the stones bigger? Then I could re-post!

I can upload it a larger size, perhaps someone will more skills can crop it and put labels of what the stone colours are underneath, that would help newbies undoubtedly and the people that appear on here weekly confused about colour when you are making suggestions!!!!

 

[30yearsofdiamonds]

GIA acid boils the sets every couple of months, this has to be done because as the sets become dirty they will actually appear lighter and thus color grades will be lower. In NY last time I checked there were 5 master sets and Carlsbad 6 or 7 sets,some date back to the eighties or earlier. They do not replace sets unless a stone is lost or damaged. No grader is assigned a set, they are assigned a one hour time slot to do approximately 50 stones and that time slot will vary during the week. Color rechecks are done in the morning and usually on the same set every day. Two graders agreeing on the same color 80% of the time on the 50 stones, is considered very good.

Any more questions, I will be happy to answer.

 

[arkieb1]

Wow, so what then happens to the 20% with split colour grades that they do not agree on? More graders look at them or do they end up the lower colour grade by default?

 

[30yearsofdiamonds]

Split grades are looked at by a third grader, usually a more experienced color grader and hopefully after that the color is finalized.

Just a note; not every diamond grader is also a color grader. It usually doesn't happen until they have been with the company for a few years and then are taught and tested for accuracy.

I will see if I can improve on the quality of the photo.

That set took 3 months to put together, it is not an easy task.

 

[Andelain]

Is there a certain size the stones have to be in a master set?

Are CZ sets anywhere near as accurate as diamond sets?

 

[30yearsofdiamonds]

Sets are between 0.70 and 1.10 usually. No UVF, no black inclusions, usually VS2 or better.

I' have checked CZ sets vs. diamond sets and in my opinion it didn't work for me. If I were to make a set for myself and wanted to do it economically, I would use 0.50 ct rounds, and I would have an E, G, I and K.

 

[30yearsofdiamonds]

Edited photo

 

[OoohShiny]

As a newbie, this thread really is very useful indeed, thank you very much for posting it!


Would it be possible / a good idea to sticky it at the top of the forum? Colours and the differentiation between them seems to always be a concern of us new people looking to buy our first stone, so it would be great to find it easily

 

[Andelain]

Sets are between 0.70 and 1.10 usually. No UVF, no black inclusions, usually VS2 or better.

I' have checked CZ sets vs. diamond sets and in my opinion it didn't work for me. If I were to make a set for myself and wanted to do it economically, I would use 0.50 ct rounds, and I would have an E, G, I and K.

Thanks, that's good to know. My next question then, how close in size should the stones be to each other?

 

[baby monster]

Love the photo. Super helpful to see the full range. Is every stone above E graded D? How wide is the D range? Will there ever be A/B/C grades? Who can decide to start grading/using above D?

 

[yssie]

What a fantastic thread - thank you so much for posting that photo 30years, and your answers to Karl's questions were very interesting! Would you mind if I ask a couple more?


-- What's the process for grading below N? I know that's where GIA begins splitting letter assignments - O/P, etc. How do the master stones in these split-letter ranges work?

-- Are the master stones always RBs? Do proportions matter at all? (I assume not).

-- How are colour grades for stones with (slight) tints other than yellow determined? Brown follows the D-Z scale as well, with a notation on the report below K - is there a "brown master set" also? And Tom Gelb describes grading of colours other than yellow/brown/grey as either colourless (D-F) or Faint, etc. on the fancy scale if the stone has an equivalent color grade of G or below. How is the strength of say a pink determined to be "G" or below, or strength of a grey determined to be "K" or below?
Do the same graders grade both colourless-yellow/brown and (slightly) coloured diamonds colourless-pink/grey/etc., or are the latter usually assigned to people with different training/expertise?


Thank you again for this fascinating thread!!

Hello Yssie,
I believe I can shed a little more light here. I worked in fancy colors at the GIA for a number of years. Please note the responses in red below. If you have anymore questions please let me know.
All the best,
Tom

No, I'm definitely not talking about fluor - only the body colour of the stone. So am I understanding correctly (w/ reference to GIA's grading only):
1. GIA will call a stone with *yellow* body colour of certain strength/saturation (let's call this "X") a K. Correct
2. GIA will call a stone with *brown* body colour of certain strength/saturation >= "X" a K, and will note that colour is due to brown on the report. From K-M Faint brown, N-R Very Light Brown, S-Z Light Brown
3. GIA will call a stone with *yellow* body colour of strenght/saturation < "X" an E-J. Correct
4. GIA will call a stone with *brown* body colour of strength/saturation < "X" an E-J, but you are unsure if there will be a brown notation. No brown noted, except on internal GIA documents
5. If the stone is cut from *pink* rough, it is either a D (completely colourless) or a Faint, Very Light, Light, Fancy, Fancy Intense, Fancy Vivid, Fancy Deep. There is no possibility of acquiring a GIA G with an inkling of *pink*. Same with *blue*. If a diamond is graded D-F it will get only a letter grade regardless of the underlying tint. Remember D-F is termed "colorless" so although there may be something there it would be quite strange for a diamond to be called both colorless and blue. If a diamond has a color other than yellow, brown or gray and has an equivalent color grade of G or below the diamond would then be graded in the fancy color grading scale starting with Faint.
[...]
7. Gray diamond are a strange exception and treated differently. The post is correct in that a diamond with a gray undertone would be graded on the D-Z color scale until it reached K color. At that point the diamond wold be graded on the GIA fancy color grading system starting with Faint Gray.
[...]

 

[yssie]

Love the photo. Super helpful to see the full range. Is every stone above E graded D? How wide is the D range? Will there ever be A/B/C grades? Who can decide to start grading/using above D?

http://4csblog.gia.edu/2011/why-start-with-d-3
When men and women really start looking into diamond grading, a common question is, “Why does the GIA color grade start with a D?”
GIA’s grading scale begins with the letter D, representing colorless, and continues, with increasing presence of color, to the letter Z. Diamonds are color-graded by comparing them to stones of known color under controlled lighting and precise viewing conditions.
Historically, metaphoric terms were used in the very old days. “River” and “water” were used for the most colorless diamonds, or they might be categorized by a geographic location from places where similarly colored diamonds were seen. For instance, there was “Cape” for pale yellow diamonds from the Cape of Good Hope.
The choice was made to differentiate the GIA grading system from other less clearly defined ones that used designations such as “A” or “AA”. Additionally, American Gem Society (AGS) had its own numerical scale, which was only for AGS member use. So when GIA chose to develop a diamond grading system, it had to use new terms. Hence, the “D.”

http://gia4cs.gia.edu/en-us/diamond-color.htm
Why does the GIA color grading system start at D?
Before GIA universalized the D-to-Z Color Grading Scale, a variety of other systems were used loosely, from A, B, and C (used without clear definition), to Arabic (0, 1, 2, 3) and Roman (I, II, III) numbers, to descriptive terms like "gem blue" or "blue white," which are notorious for misinterpretation. So the creators of the GIA Color Scale wanted to start fresh, without any association with earlier systems. Thus the GIA scale starts at the letter D. Very few people still cling to other grading systems, and no other system has the clarity and universal acceptance of the GIA scale.

 

[30yearsofdiamonds]

Tom and I worked together and what he wrote is correct, so I am not going to repeat it.

The masters are generally the same size or very close in size.

Older sets are not necessarily triple excellent.

All masters are RBC.

GIA now has a brown master set to grade brownish diamonds.

After the N color grade, GIA splits the grade because they do not have a master stone for each letter designation, they take an educated guess at the range.

 

[yssie]

Thank you for the additional information! Very interesting to hear that there is a brown set as well, and your first comment helps explain why I have always heard that grading of O/P - Y/Z is a much less repeatable process, and that helps explain why there isn't a rigid pricing structure as there is for colourless-faint colour.

Re. the last - forgive me if my question was unclear. I am not questioning Tom Gelb's response, but hoping you can tell us more about how these sorts of stones are graded. For example, how is the "strength of colour" of a diamond with underlying pink body colour determined to be G or below to merit being handed off to be assigned a Fancy grade based on face-up colour? Is there a "Faint pink" master stone, or something like that, above which the stone is considered "colourless D-F" in terms of body colour?

 

[chrono]

Colour grades added.

 

[purplesparklies]

I have a stone that was graded by GIA prior to a recut by BGD. I am curious if it would be likely to grade differently color &/or clarity wise after the recut. Is a recut likely to make a difference?

 

[Andelain]

I have a stone that was graded by GIA prior to a recut by BGD. I am curious if it would be likely to grade differently color &/or clarity wise after the recut. Is a recut likely to make a difference?

Yes, there's a decent change it will. I had a stone go from near the end of the alphabet to an N when Brian took it from a .99 'cut like a truck' to a .80 AGS0.