When are IS, ASET, and/or reflector technologies needed or not needed for internet purchasing…(?)

[Rhino]

Hi Serg,

Date: 11/7/2008 11:45:06 AM
Author: Serg

Rhino,


Does this stone have Pavilion digit-out?

Not enought that would have caused it to take a hit in the GIA system. It was an Ex grade. I may have a Helium on it with precise measurements.

If yes, Optical Symmetry is irrelevant explanation for downgrade

Diamond with Digit-out or painting could have High level symmetry .

I understand your point because I have seen (and have scans of) diamonds with painting and digging that don''t make Ex or Ideal with the high level symmetry you''re talking about. To my knowledge not the case here but even if it were Serg ... the leakage under the table is not being caused by painting and digging. Painting and digging would impact brightness around the crown. Leakage however, under the table would not be caused by the painting/digging. All of it however impacting the PGS grade.


P/s for Karl. This is not example what PGS sensitive to symmetry. ( Most probably digit-out is reason)

Just curious ... how much digging is allowed on the pavilion in GIA and AGS gold systems? I''ve been focusing on crown painting and digging as that''s what I run into more.

Peace,

 

[michaelgem]

MYOPIA???

Let''s look at simplifications of Ideal round brilliant cut grading, such as those in the Journal Accordance article. This work includes details of commonalities between GIA and AGS charts and tables. Let''s look at the use of those charts and tables by GIA and now AGSL to communicate their cut grading systems and grade boundaries. These simplifications, which many believe are essential to understanding and practical utilization, are viewed by some as myopic, over-simplification.

My myopia (near-sightedness) allows me to notices details in small objects like gemstones that often go unnoticed by many. When it comes to diamonds, “cut nuts” or “diamond mavens” notice detail that is often unseen by most in usual diamond viewing. A good example is the subtle leakage and retroflection variations in the middle ring or iris of the “diamond eye” due to slight change in crown or pavilion main angles. These variations occur even within the sweet spot ranges of both AGS and GIA. As several have explained in the past, the effect of these variation''s on light performance is exaggerated by their representation in reflector devices, and consequently in the minds of those using them.

The attention to details, such as minor amounts of white leakage in reflector devices, at some level, has little to do with perceived light performance. In the case of slightly steeper and deeper round brilliants, it can explain why many see performance problems, while the GIA and their extensive comparison testing finds them to be EX. Past some point, all agree that steep/deep, just as shallow/shallow, exhibits poor light performance. But as you move from the Ideal combination (41°, 34°, 56%) in the steep/deep direction, the diamond reflects more from wider angles, better avoiding head obstruction. Decreased viewer obstruction explains positive results from observation testing by GIA for slightly steep/deep cuts, carried out in jewelry stores and other usual viewing circumstances. The comparison testing finds slightly steep/deep diamonds, that are just beginning to exhibit middle ring problems, to be judged by most as more, not less, brilliant than even the Tolkowsky Ideal. It appears from this comparison testing that the better perceived brightness of the slightly steep/deep proportions more than compensates for any slight middle ring problems in typical viewing and illumination conditions.

This is a simple explanation of just one example of the differences between what we "mavens" see that most consumers and jewelers in their viewing circumstances may see differently. This understanding causes many of us, myself included, to advocate a tighter sweet spot than either AGS Platinum, Gold or GIA EX. The Journal article noted that I and others “set the bar for the best make higher in some respects than either GIA or AGS.” While this may be fine for the perfectionists among us, if a lab downgrades a diamond cut, whose visual appearance is as good or better than another, in a very real sense, rather than a service, they may be doing a disservice to both the consumer and the cutter.

While acknowledging that my explanations, here and in my article, along with chart representations, like the AGS Gold, may be seen as myopic over simplifications, they are essential for education and understanding by jewelers, gemologist-appraisers, cutters and others in the trade. GIA and now AGS believe they provide a practical and essential way for the cutter to understand and optimize his cut planning. We agree to disagree that nothing material to overall light performance and diamond beauty is being lost or compromised in the use of charts and tables to communicate a cut grading system.

As an example of Occam''s razor, charts and tables are the simplest solution for the cutter, jeweler and ultimately the consumer that is adequate and sufficient to the task. GIA has been demonstrating this for over 2 years. The effective use of these charts by Sergey''s group to communicate the AGS PGS system and others for his clients is further proof. Sergey''s, GIA''s and AGS''s charts, and for that matter, the Accordance article''s explanation of them, are essential rather than myopic simplifications for cut grade understanding and usage by all.
Michael D. Cowing

PS: And I see a greater myopia in those who dismiss or fail to learn from charts like those Sergey''s group has generated with the PGS software.

 

[Rhino]

Date: 11/7/2008 4:55:30 PM
Author: Serg

Date: 11/7/2008 4:48:37 PM
Author: strmrdr
Jon it has been suggested that the difference might not be eye visible since you saw both please comment on that.

Yes I was able to see the difference. In fact I have saved all of this data for a teaching video on the subject and have recorded brightness, contrast (patterned scintillation), fire and sparkle scintillation differences between these 2.

In a nutshell ...

Practical observation revealed that brightness and contrast were impacted moreso than fire and sparkle. Fire and sparkle were really tough to tell any difference at all and in fact BrillianceScope results on the 1.75ct wonky stone also turned out very good (as Brilliancescope tests in spot lighting, not diffuse).

So ... yes there is a difference that I could see. Not quite the jump to a trainwreck of a difference but a decrease in brightness/contrast enough that I would not purchase the diamond nor recommend it to a client.

All the best,

 

[Rhino]

Hey Ira,

Thoughts below.

Date: 11/7/2008 12:52:22 PM
Author: Regular Guy
Thanks, gentlemen.

Am I following the ball on this?

Three questions, to at least Jon:

1)

Is the one that was on the right where there was a picture here...

Date: 11/6/2008 9:19:10 PM
Author: Rhino
DiamXray shows an obvious difference. The pavilion facets on one show superior reflections off the pavilion while the other demonstrates some notable leakage under the table.

...the one that showed leakage (but scored better using the ISEE2 technology)...that was the one that uniquely gets 0 as in AGS platinum...and not the other one without the leakage, which gets a 3?

I think you got it right now because I saw your latter post. To be clear, the inferior diamond with the wonky optical symmetry got the lower Isee2 score. Isee2 graded them both right on. BTW the lower Isee2 score is the result of
a. the leakage aspect
b. the lack of Optical Symmetry.

One thing the Isee2 can not do however (at this time) is *see* the effects of painting or digging. I rely on other exams for that.

I''ll say that again...

was your result:

per reflector technology

leakage = 0 from PGS (= Platinum zero)

non-leakage = 3 from PGS ( and an AGS Platinum 3)

Nope. I see strm corrected your understanding though.

-----------------

2) If I''m correct above (and I may not be), which one did you prefer, anyway.

The one that rocked all the evidence. As noted in my previous post I could see the difference between the 2 and have recorded, to the best of my ability what I have seen.

3) Why?

As noted, primarily brightness and contrast (patterned scintillation). It''s been a little while since I had both before my eyes but a quick review of the recording would jog my memory real fast. Whenever I record I always speak into the mic about what it is that I am observing.

-

Hope that helps.

All the best,

 

[Rhino]

Date: 11/7/2008 5:01:07 PM
Author: strmrdr

Date: 11/7/2008 4:56:22 PM
Author: jasontb
I would expect that it would be quite easy to see the difference between an AGS0 and an AGS3 (as somebody who doesn''t know too much about these grading systems, especially regarding where they break down and lead to inconsistencies).


Am I wrong to necessarily expect such a difference?

In the other thread Garry and myself are in agreement that there would be a large difference.
Jon can settle this when he stops by.
I actually think its twilight zone material to suggest that there is no visible difference between the 2.
Under table leakage stands out like a sore thumb to me.

If memory serves me right that was the most notable feature I was able to see strm. The results of the table leakage. I am intimately familiar with what painting and digging look like too and don''t like either but I can''t recall at this moment if the digging was enough to ding the optics. I''d have to find the clip. BTW I also have the .dmc file of the wonky stone as generated via the Helium. Are we able to upload those files here or are they too large for PS?

 

[strmrdr]

Date: 11/7/2008 6:05:45 PM
Author: Rhino
Are we able to upload those files here or are they too large for PS?

save it as a gem file then you can upload it.
or just post a link to it.
Email me the full dmc file please.

 

[Serg]

Date: 11/7/2008 5:31:30 PM
Author: Rhino
Hi Serg,

Date: 11/7/2008 11:45:06 AM
Author: Serg

Rhino,


Does this stone have Pavilion digit-out?

Not enought that would have caused it to take a hit in the GIA system. It was an Ex grade. I may have a Helium on it with precise measurements.

If yes, Optical Symmetry is irrelevant explanation for downgrade

Diamond with Digit-out or painting could have High level symmetry .

I understand your point because I have seen (and have scans of) diamonds with painting and digging that don''t make Ex or Ideal with the high level symmetry you''re talking about. To my knowledge not the case here but even if it were Serg ... the leakage under the table is not being caused by painting and digging. Painting and digging would impact brightness around the crown. Leakage however, under the table would not be caused by the painting/digging. All of it however impacting the PGS grade.



P/s for Karl. This is not example what PGS sensitive to symmetry. ( Most probably digit-out is reason)

Just curious ... how much digging is allowed on the pavilion in GIA and AGS gold systems? I''ve been focusing on crown painting and digging as that''s what I run into more.

Peace,

re:the leakage under the table is not being caused by painting and digging. Painting and digging would impact brightness around the crown. Leakage however, under the table would not be caused by the painting/digging. All of it however impacting the PGS grade.

Rhino,

1) Open DC
2) Change P. to 41
3) Turn on IS light. No leakage
4) Do digit pavilion half’s 2 degree( You need azimuth 13.25) . Now you see leakage

 

[Garry H (Cut Nut)]

Date: 11/7/2008 6:05:45 PM
Author: Rhino

Date: 11/7/2008 5:01:07 PM
Author: strmrdr

Date: 11/7/2008 4:56:22 PM
Author: jasontb
I would expect that it would be quite easy to see the difference between an AGS0 and an AGS3 (as somebody who doesn''t know too much about these grading systems, especially regarding where they break down and lead to inconsistencies).


Am I wrong to necessarily expect such a difference?

In the other thread Garry and myself are in agreement that there would be a large difference.
Jon can settle this when he stops by.
I actually think its twilight zone material to suggest that there is no visible difference between the 2.
Under table leakage stands out like a sore thumb to me.

If memory serves me right that was the most notable feature I was able to see strm. The results of the table leakage. I am intimately familiar with what painting and digging look like too and don''t like either but I can''t recall at this moment if the digging was enough to ding the optics. I''d have to find the clip. BTW I also have the .dmc file of the wonky stone as generated via the Helium. Are we able to upload those files here or are they too large for PS?

Make sure you save it in the small format Jonathon - because you have Helium you generally save Gem Adviser files with all the data - that will be too big to post here. Or send any of us any format and any of us can post it

If you still have the stone can you make the pavilion a bit greasy and examine it with minimal back light (like it was set in a ring or pendant) please?

 

[Moh 10]

I''d say an AGS 0 round or princess makes all that stuff unnecessary . . . well . . . probably, that is.

Seriously, an AGS 0 cut grade sets the bar very high.
Sure, if you do lots of homework, review the data from all those tools you mentioned you can cherry-pick among a bunch of AGS 0s to get the best of the best of the best.

But if a newbie just wants to buy something right away without much effort an AGS 0 cut diamond is a very very high standard.

 

[michaelgem]

Date: 11/7/2008 6:26:17 PM
Author: Serg

Date: 11/7/2008 5:31:30 PM
Author: Rhino
Hi Serg,

Date: 11/7/2008 11:45:06 AM
Author: Serg

Rhino,

Does this stone have Pavilion digit-out?

If yes, Optical Symmetry is irrelevant explanation for downgrade

Diamond with Digit-out or painting could have High level symmetry .

P/s for Karl. This is not example what PGS sensitive to symmetry. ( Most probably digit-out is reason)

Rhino,

1) Open DC
2) Change P. to 41
3) Turn on IS light. No leakage
4) Do digit pavilion half’s 2 degree( You need azimuth 13.25) . Now you see leakage

Sergey is right

With both diamonds proportions being in the heart of Ideal/EX land, and both having VG symmetry, these stones should be indistinguishable. The asymmetry causing the leakage must be due to digging that the symmetry measure is not seeing. That makes this example less than useful as an argument.

It does point to reflector devices'' ability to catch this problem, where the symmetry analysis from the sarin scan misses it. Since both stones have VG symmetry and one has beautiful optical symmetry, I would conclude: If both had VG symmetry with normal indexing they would have had similar performance, so unmeasured painting or digging must be at work in the other stone.

It also points out a problem with my argument that averaging doesn''t hurt chart systems when high symmetry requirements are imposed. I have argued that by requiring high symmetry, there would be little variance in parameters, so using a sufficiently accurate average would introduce negligible error. This may still be operative for normally indexed stones.

This one stone has less than VG symmetry, yet it seems to have been missed. I should be saying that chart systems work well with stones with high symmetry as checked from the girdle pattern, or have high optical symmetry as checked with reflector devices.

This is an acknowledgment of points made by Karl, Ira and others. Reflector devices alert to light performance problems that may be missed by sarin scan analysis.

From past posts, you would know I am a big proponent of the light performance virtues of optical symmetry. I do not think either lab takes it into enough consideration as a requirement for top grade status.

With these acknowledged caveats, you may find my previous, badly timed, post more reasonable.

Michael D. Cowing

 

[strmrdr]

Michael,
I think we finely may be communicating rather than talking around each other.

 

[michaelgem]

Date: 11/7/2008 11:05:10 PM
Author: strmrdr
Michael,
I think we finely may be communicating rather than talking around each other.

Well, we are both struggling to express some complex issues. At the same time, I am aware and understand the issues you raise. I just needed to take the opportunity to acknowledge them. And emphasize the assumptions and limitations in predicting a diamond''s light performance from charts. As Sergey and I have said, these charts are created with assumptions of mathematical symmetry, normal indexing and nominal values for the minor facets. As such they are a best case grade for those proportion conditions, and do not guarantee the grade, only indicate the highest grade likely to be obtained.

I think it is reasonable to believe, if you produce a VG to EX symmetry stone cut to the charts top grade with normal indexing and similar minor facets, you should get the grade. I believe Sergey''s cutter clients have shown this in practice. It is also reasonable then to believe, if the stone can be shown to have reasonable optical symmetry, and if the charts indicate Ideal or EX the grade is predictive enough to be used as a selection system. But maybe I''m pushing my luck too much at the end here.

Michael

 

[Regular Guy]

Date: 11/8/2008 12:38:04 AM
Author: michaelgem

I think it is reasonable to believe, if you produce a VG to EX symmetry stone cut to the charts top grade with normal indexing and similar minor facets, you should get the grade. I believe Sergey's cutter clients have shown this in practice. It is also reasonable then to believe, if the stone can be shown to have reasonable optical symmetry, and if the charts indicate Ideal or EX the grade is predictive enough to be used as a selection system. But maybe I'm pushing my luck too much at the end here.

Michael

What I think its reasonable to do is look at the cost, function, and value sought from grading. By anybody, I suppose. But, yes, I'll focus on the consumer.

Consider a child, niece, or good friend of yours would be shopping for an engagement ring. Then...look at how many if's are in you text above.

It seems to me, you could send them out to shop for zero platinum. And, or, with a $25 check and instructions to purchase their own Idealscope, you could tell them to get a GIA EX or AGS gold, and use the IS. But...failing the second set of instructions, you may want to supplement your advice with the add on: "You're darn likely to get a winner!"

 

[strmrdr]

Date: 11/8/2008 12:38:04 AM
Author: michaelgem
I think it is reasonable to believe, if you produce a VG to EX symmetry stone cut to the charts top grade with normal indexing and similar minor facets, you should get the grade. I believe Sergey's cutter clients have shown this in practice. It is also reasonable then to believe, if the stone can be shown to have reasonable optical symmetry, and if the charts indicate Ideal or EX the grade is predictive enough to be used as a selection system. But maybe I'm pushing my luck too much at the end here.

Michael

To many assumptions in the above for me.
I always judge any grading system worse case.
Any system can pick out the known best and call it good the real quality of a system comes from how well it separates out the not best and prevents negative tricks, if it rewards positive tricks all the better.
AGS Gold fails both of those tests so it can not be used for selection.

 

[Rhino]

Date: 11/7/2008 6:26:17 PM
Author: Serg

Date: 11/7/2008 5:31:30 PM
Author: Rhino
Hi Serg,

Date: 11/7/2008 11:45:06 AM
Author: Serg

Rhino,


Does this stone have Pavilion digit-out?

Not enought that would have caused it to take a hit in the GIA system. It was an Ex grade. I may have a Helium on it with precise measurements.

If yes, Optical Symmetry is irrelevant explanation for downgrade

Diamond with Digit-out or painting could have High level symmetry .

I understand your point because I have seen (and have scans of) diamonds with painting and digging that don''t make Ex or Ideal with the high level symmetry you''re talking about. To my knowledge not the case here but even if it were Serg ... the leakage under the table is not being caused by painting and digging. Painting and digging would impact brightness around the crown. Leakage however, under the table would not be caused by the painting/digging. All of it however impacting the PGS grade.




P/s for Karl. This is not example what PGS sensitive to symmetry. ( Most probably digit-out is reason)

Just curious ... how much digging is allowed on the pavilion in GIA and AGS gold systems? I''ve been focusing on crown painting and digging as that''s what I run into more.

Peace,

re:the leakage under the table is not being caused by painting and digging. Painting and digging would impact brightness around the crown. Leakage however, under the table would not be caused by the painting/digging. All of it however impacting the PGS grade.

Rhino,

1) Open DC
2) Change P. to 41
3) Turn on IS light. No leakage
4) Do digit pavilion half’s 2 degree( You need azimuth 13.25) . Now you see leakage

Thank you for this Serg. I''ve never tried that within DC before and am a bit rusty in adjusting azimuth angles on the fly. I see the new feature in DC 3.0 on "Advanced 2" tab and did it. Interesting. Isn''t there also another way of adjusting individual facets azimuth angles too? If so please link me.

There is in fact pavilion digging on this diamond of 2.85 degrees.

Attached is the simple .gem file.

 

[Rhino]

Date: 11/7/2008 7:50:23 PM
Author: Garry H (Cut Nut)
Make sure you save it in the small format Jonathon - because you have Helium you generally save Gem Adviser files with all the data - that will be too big to post here. Or send any of us any format and any of us can post it

If you still have the stone can you make the pavilion a bit greasy and examine it with minimal back light (like it was set in a ring or pendant) please?

Hi Garry,

The diamond is not in my possession anymore. I''d like to take the model of this and *readjust* the digging on the pavilion to see what happens. I see the "advanced edit" and its coming back to me.

 

[michaelgem]

Date: 11/8/2008 8:38:56 AM
Author: Regular Guy

Date: 11/8/2008 12:38:04 AM
Author: michaelgem

I think it is reasonable to believe, if you produce a VG to EX symmetry stone cut to the charts top grade with normal indexing and similar minor facets, you should get the grade. I believe Sergey''s cutter clients have shown this in practice. It is also reasonable then to believe, if the stone can be shown to have reasonable optical symmetry, and if the charts indicate Ideal or EX the grade is predictive enough to be used as a selection system. But maybe I''m pushing my luck too much at the end here.

Michael

What I think its reasonable to do is look at the cost, function, and value sought from grading. By anybody, I suppose. But, yes, I''ll focus on the consumer.

Consider a child, niece, or good friend of yours would be shopping for an engagement ring. Then...look at how many if''s are in you text above.

It seems to me, you could send them out to shop for zero platinum. And, or, with a $25 check and instructions to purchase their own Idealscope, you could tell them to get a GIA EX or AGS gold, and use the IS. But...failing the second set of instructions, you may want to supplement your advice with the add on: ''You''re darn likely to get a winner!''

Great way of putting it, Ira.

I think that both GIA''s and AGS''s Chart communicated grading systems have built in limits on symmetry, spread, painting and digging that they believe guarantee the grade''s light performance, while at the same time allowing the cutter to get the best yield in ways not noticably harmfull to diamond beauty.

To the degree each lab has succeeded, these chart systems are selection systems. However, we all agree that the current symmetry requirements are allowing or just failing to see asymmetries that do negatively and noticably impact light performane.

So, as much as I believe both GIA and AGS intend to protect the consumer with a selection system, while not imposing unnecessary requirements on the cutters, neither is so far succeeding in our opinions. My arguement is that these two chart systems can be good selection systems if the symmetry requirements are adequately strengthened.

Then my niece can give me back my IS.

Michael

 

[michaelgem]

Date: 11/8/2008 9:29:28 AM
Author: strmrdr

Date: 11/8/2008 12:38:04 AM
Author: michaelgem
I think it is reasonable to believe, if you produce a VG to EX symmetry stone cut to the charts top grade with normal indexing and similar minor facets, you should get the grade. I believe Sergey''s cutter clients have shown this in practice. It is also reasonable then to believe, if the stone can be shown to have reasonable optical symmetry, and if the charts indicate Ideal or EX the grade is predictive enough to be used as a selection system. But maybe I''m pushing my luck too much at the end here.

Michael

To many assumptions in the above for me.
I always judge any grading system worse case.
Any system can pick out the known best and call it good AGS Gold fails both of those tests so it can not be used for selection.

Fair assessment, Karl,

I especially like your comment: the real quality of a system comes from how well it separates out the not best and prevents negative tricks, if it rewards positive tricks all the better.

As I said to Ira: as much as I believe both GIA and AGS intend to protect the consumer with a selection system, while not imposing unnecessary requirements on the cutters, neither is so far succeeding in our opinions.

My arguement is that these two chart systems can be good selection systems if the symmetry requirements are adequately strengthened.

In the mean time, it''s necessary to be aware of the caveats of sufficient optical symmetry and nominal proportions for the minor facets (which are not really minor), as I continue, through the use of these charts, to explain and communicate an understanding of both GIA''s and AGS''s grading systems . As I believe Sergey, I and others have demonstrated: Charts are essential for education and understanding of these systems by cutters, jewelers, gemologist-appraisers, and ultimately, this knowledge can indirectly or directly benefit the consumer.

Michael

 

[Finally!]

Rhino,

This gets back to my question from a different thread, which Ira referenced in the first post of this thread. WHY did the cutter do the pavilion digging? I''m assuming it was done on purpose and was not a mistake. What benefit did it bring to the cut?

 

[Rhino]

Date: 11/8/2008 1:00:53 PM
Author: michaelgem

Date: 11/8/2008 8:38:56 AM
Author: Regular Guy

Date: 11/8/2008 12:38:04 AM
Author: michaelgem

I think it is reasonable to believe, if you produce a VG to EX symmetry stone cut to the charts top grade with normal indexing and similar minor facets, you should get the grade. I believe Sergey''s cutter clients have shown this in practice. It is also reasonable then to believe, if the stone can be shown to have reasonable optical symmetry, and if the charts indicate Ideal or EX the grade is predictive enough to be used as a selection system. But maybe I''m pushing my luck too much at the end here.

Michael

What I think its reasonable to do is look at the cost, function, and value sought from grading. By anybody, I suppose. But, yes, I''ll focus on the consumer.

Consider a child, niece, or good friend of yours would be shopping for an engagement ring. Then...look at how many if''s are in you text above.

It seems to me, you could send them out to shop for zero platinum. And, or, with a $25 check and instructions to purchase their own Idealscope, you could tell them to get a GIA EX or AGS gold, and use the IS. But...failing the second set of instructions, you may want to supplement your advice with the add on: ''You''re darn likely to get a winner!''

Great way of putting it, Ira.

I think that both GIA''s and AGS''s Chart communicated grading systems have built in limits on symmetry, spread, painting and digging that they believe guarantee the grade''s light performance, while at the same time allowing the cutter to get the best yield in ways not noticably harmfull to diamond beauty.

To the degree each lab has succeeded, these chart systems are selection systems. However, we all agree that the current symmetry requirements are allowing or just failing to see asymmetries that do negatively and noticably impact light performane.

So, as much as I believe both GIA and AGS intend to protect the consumer with a selection system, while not imposing unnecessary requirements on the cutters, neither is so far succeeding in our opinions. My arguement is that these two chart systems can be good selection systems if the symmetry requirements are adequately strengthened.

Then my niece can give me back my IS.

Michael

Greetings my friend!!! Good to cya on the boards.

Strengthening up the symmetry ... now that''s hitting the nail on the head. Do I take your statment to mean that GIA and AGS should be strengthening "Optical Symmetry" or tradition meet point symmetry? If meet point this one gets Ex. This is a good case for optical symmetry eh?

All the best,

 

[Rhino]

Date: 11/9/2008 7:03:47 PM
Author: Finally!
Rhino,

This gets back to my question from a different thread, which Ira referenced in the first post of this thread. WHY did the cutter do the pavilion digging? I'm assuming it was done on purpose and was not a mistake. What benefit did it bring to the cut?

Why is a good question Finally. Obviously it did not benefit the cut. There could be a number of reasons. Whatever the reason was it wasn't good enough to earn my dollar or my recommendation. There is only so much one can glean from straight numbers and a report regarding cut and that's not to mention the nature of the inclusions, etc. all of which can not be determined without a live examination. We recently ran into another diamond that had the most perfect numbers you could image and a VVS2 clarity to boot. The inclusion however penetrated the surface and was open and was on the crown.

 

[Garry H (Cut Nut)]

Date: 11/9/2008 7:03:47 PM
Author: Finally!
Rhino,

This gets back to my question from a different thread, which Ira referenced in the first post of this thread. WHY did the cutter do the pavilion digging? I''m assuming it was done on purpose and was not a mistake. What benefit did it bring to the cut?

Many people have wondered why there is a weight saving to be had with painting and digging - one question is:

If it saves weight - why are not all stones treated that way?
I hope this picture explains why
This stone has a dug crown and a painted pavilion.
There are 4 possible options and this excellent article from brian Gavin shows the variants and ASET images for the results.
This link comes in on about page 3 I think
http://journal.pricescope.com/Articles/45/2/Visible-Effects-of-Painting--Digging-on-Superideal-Diamonds.aspx

 

[Rhino]

Thanks for the example Garry. As you examine the model on this particular do you think it was done for weight retention being at 1.75ct? How much more weight do you think was retained in this particular example or is it hard to say?

Regards,

 

[Garry H (Cut Nut)]

Date: 11/9/2008 9:19:36 PM
Author: Rhino
Thanks for the example Garry. As you examine the model on this particular do you think it was done for weight retention being at 1.75ct? How much more weight do you think was retained in this particular example or is it hard to say?

Regards,

Say this was a 6.4mm stone that would make 1ct with the swindling of digging and painting.
In order to achieve a regular girdle the stone may need to be 6.3mm and loose 0.02ct.
So the answer might only be 2%, but it is a critical 2%

Janak has sent a group of us another excellent example that I will ask him to be allowed to submitted as a journal article.

 

[Regular Guy]

So Garry, and Finally, the stone in Finally''s original example weighted in at 1.31 carats. I maybe see a little clearer now...along with a reminder of Brian''s explanation at the bottom of the first page of his article...that these are strategies for retaining weight. But...since cutters just don''t always try to do this...with this particular stone...and ostensibly already (?) good performance, why the brillianteering?

It would not have been to just make either 1 or 1.5 carats.

 

[strmrdr]

Date: 11/9/2008 7:40:22 PM
Author: Garry H (Cut Nut)

Date: 11/9/2008 7:03:47 PM

Author: Finally!

Rhino,


This gets back to my question from a different thread, which Ira referenced in the first post of this thread. WHY did the cutter do the pavilion digging? I'm assuming it was done on purpose and was not a mistake. What benefit did it bring to the cut?

Many people have wondered why there is a weight saving to be had with painting and digging - one question is:

If it saves weight - why are not all stones treated that way?

I hope this picture explains why

This stone has a dug crown and a painted pavilion.

There are 4 possible options and this excellent article from brian Gavin shows the variants and ASET images for the results.

This link comes in on about page 3 I think

http://journal.pricescope.com/Articles/45/2/Visible-Effects-of-Painting--Digging-on-Superideal-Diamonds.aspx

Garry with some very careful selection a dug crown and a painted pavilion can be made to work together. Maybe not AGS PGS0 level but certainly AGS PGS1 level.
A 3D system can reward that a 2D system cant separate a bad one from a good one.

 

[Garry H (Cut Nut)]

Date: 11/10/2008 1:00:44 AM
Author: strmrdr

Garry with some very careful selection a dug crown and a painted pavilion can be made to work together. Maybe not AGS PGS0 level but certainly AGS PGS1 level.
A 3D system can reward that a 2D system cant separate a bad one from a good one.

In fact I frequently see painted stones where the painting is beneficial in slightly steep deep stones Karl.
I am not against it per se

 

[Garry H (Cut Nut)]

Date: 11/9/2008 11:01:45 PM
Author: Regular Guy
So Garry, and Finally, the stone in Finally''s original example weighted in at 1.31 carats. I maybe see a little clearer now...along with a reminder of Brian''s explanation at the bottom of the first page of his article...that these are strategies for retaining weight. But...since cutters just don''t always try to do this...with this particular stone...and ostensibly already (?) good performance, why the brillianteering?

It would not have been to just make either 1 or 1.5 carats.

1.3ct gets a bonus over 1.29ct
So they might have gained 2% weight, 3-4% for 1.30ct which is very liquid - say = +1%.
They probably were not happy about being dinged for brillianteering - but could still have come out in front

 

[strmrdr]

Date: 11/10/2008 1:15:44 AM
Author: Garry H (Cut Nut)

Date: 11/10/2008 1:00:44 AM

Author: strmrdr


Garry with some very careful selection a dug crown and a painted pavilion can be made to work together. Maybe not AGS PGS0 level but certainly AGS PGS1 level.

A 3D system can reward that a 2D system cant separate a bad one from a good one.

In fact I frequently see painted stones where the painting is beneficial in slightly steep deep stones Karl.

I am not against it per se

I know that.
I should have just made it a statement rather than address it to you.
Bad wording on my part, I''m sorry.

 

[strmrdr]

Date: 11/10/2008 1:17:54 AM
Author: Garry H (Cut Nut)

Date: 11/9/2008 11:01:45 PM

Author: Regular Guy

So Garry, and Finally, the stone in Finally''s original example weighted in at 1.31 carats. I maybe see a little clearer now...along with a reminder of Brian''s explanation at the bottom of the first page of his article...that these are strategies for retaining weight. But...since cutters just don''t always try to do this...with this particular stone...and ostensibly already (?) good performance, why the brillianteering?


It would not have been to just make either 1 or 1.5 carats.

1.3ct gets a bonus over 1.29ct

So they might have gained 2% weight, 3-4% for 1.30ct which is very liquid - say = +1%.

They probably were not happy about being dinged for brillianteering - but could still have come out in front

If I had the money to get it off the ground I would have some of my designs cut and sell them based on size and performance rather than weight.
IE. all 7MM monster asschers will sell for the same price if they are the same clarity/color.
It would be an interesting experiment and free the cutter to cut the best possible finished stones from the rough within tight tolerances for performance and looks rather than tight weight requirements.