GIA Diamond Cut Grading: Problems with Diamond Dock

[Rhino]

Date: 3/19/2006 8:14:59 PM
Author: JohnQuixote

Date: 3/19/2006 7:34:15 PM
Author: Rhino

In my conversations with Al Gilbertson he had stated that one of the staff members on the cut research team REALLY liked one of the Grade 3''s that were a shallow/shallow. I couldn''t help but think of Garry.

And after reexaming some of our older stock stones of the like, I totally understand how one could prefer that. The dudes on both cut teams (GIA & AGS) are hoping that their research encourages more people to *look* at diamonds to better understand what their personal preferences really are. Who knows ... ones personal preference may be for an AGS 4?!?

Agreed. There are combinations of steep a bit outside of AGS'' paradigms or shallow a bit outside GIA''s paradigms that will appeal to people. I think we''re fine with that. But don''t you agree that most people would not prefer a 1.28 with the face-up spread of a 1.16 (for example)...if they were aware that this was the case?

Absolutely John and excellent point.

While certain optical properties may boil down to peronal preference, if you take the fringes of each cut system regarding depth vs the typical goodies the conneisuers look out for in places like here ... a 60.x or 61.x depth will always win out over a 62.7 or 63%

Peace,

 

[Rhino]

Date: 3/19/2006 8:40:03 PM
Author: adamasgem

Date: 3/19/2006 7:45:31 PM
Author: Rhino

For the edification of all here are gem files. Marty ... you can drag these files into the DiamCalc and they''ll open up in there. If you''d like the more detailed .dmc files as generated through a Helium scan I''ll forward them to you via email.

So nobody is confused the next two files I''m going to post are from our survey of a GIA Ex 35.1 crown angle 41.2 pavilion angle. The diamond is a 1.01ct D VS2 and Pete has confirmed with me that the stone would be an AGS 1 in their current system.

Thanks Rhino for the two scans..

The pleasure is mine man. And about the misunderstanding ... don''t sweat it man. It''s not the first time I''ve been misunderstood and probably won''t be the last.

Wanna check out the Helium .dmc''s for the nitty gritty?

 

[adamasgem]

Date: 3/19/2006 8:54:37 PM
Author: strmrdr
Hey I resent being called ''Frankenstein''
There is a ultimate diamond cut.. the tech just cant make or measure it yet :}
Till then the ones with the least compromises will have to do :}

Stmrdr. a/k/a Frankenstein join the crowd looking for the "answer".

The problem is defining what "envirionments" are "correct for showing the compromises you have to make... and presenting them in a balanced way. You may only spend 40 hours a week in the "office", but you spend a lot more time in social occations or at home, whee the lighting conditions are entirely different. DD seems to present only one of the conditions..and is strongly influenced by the tray and the intensity of the lighting, as well as the viewpoint.

 

[Shay37]

I think that PS has made a lot of Frankensteins.

Love these tekkie discussions. Just a comment or two. I know that there are lots of consumers who will never care about the most important C for diamond beauty. There are others who will care if they are educated about it and the effects that it has on a diamond''s sparkle factor. Whether or not I agree with the downgrading of a painted or the inclusion of some steep/deep combos in the GIAs top grade, the one thing I do note as positive is that now there is a reference to cut on a GIA cert that does not mean the shape of a diamond. Cannot tell the times I''ve asked about cut to be told it''s round.

A lot of the jewelry stores around here offer either GIA or EGL. Most do not offer diamonds with AGS certs. So the one cert with cut info for the longest time has been pretty unavailable by and large to Joe Q Public. This is at least a step forward for most people not doing research on line to be able to know that cut is important. It''s not a complete step by any means, but it''s a definite start. Now, if we could just outlaw jeweler''s lights for the making of the dogs into the dolls at least until you pay and get them home. Ahhh, but that''s a topic for another day.

Keep it coming guys. I''m enjoying the byplay.

shay

 

[Rhino]

Evenin mate,

Date: 3/19/2006 8:24:23 PM
Author: Garry H (Cut Nut)
An interesting thought:

I was surprised that a retailer would use a typical dealers lighting to judge the cut quality of a diamond. Rhino uses the Geisen twin fluoro for example (I think you wrote that rhino?).

Correct. Have you ever seen this before? The lighting is calibrated 5800 degree kelvin and has a diffuser place that you can slide in and out at will. When I am demonstrating to clients the difference between brightness and fire it comes in handy. The diffuser plate in does a good job of showing brightness, take the diffuser plate out and ... well ... you can hear Earth Wind and FIRE!!!.

http://www.gesswein.com/catalog/catalog.cfm?cat=16&sub=2&subsub=3&catalog=1&CFID=657062&CFTOKEN=74146495

Using this temperature of lighting when showing clients Garry also made me realize the importance of a neautral colored background which addresses the point you bring up later in this post ...

When ever i have been buying in dealers environs - I never make decisions in that lighting & I am asking myself why? (perhaps instinctively - perhaps because it disagreed with my Ideal-scope / FS observations - I dont know when or why I stopped or changed).

Sergey has shown now that this is really bad, and shown why. I always knew that looking at inclusions with backlight thru the diamond was bad news for cut grading - even though I have seen countless thousands of merchants, graders and appraiser students do it. And a typical dealer has a big white pad on the desk just to make the environment worse.

TOTALLY AGREE!

I think back to some of my debates with Brad and Jan - and it is clear now why they believe what they believe - I thought at the time that they were simply allowing back light to enter the pavilion because the way they took their photo's - but actually they too probably use strong desk liights!!!

How do we get the trade to change to using consumer type lighting?
How do we stop this stoopid usage of LED lamps sitting on desks so people can see the fire in a diamond?

I think you mean fire under LED's? Most dealers have non-diffused fluorescent tube lighting like this.
http://www.gesswein.com/catalog/catalog.cfm?cat=16&sub=1&subsub=6&catalog=1&CFID=657062&CFTOKEN=74146495

The problem with dealer lighting: Daylight fluorescent with a white/bright paper backdrop is on the desks of most dealers and making crapola look good. I think we are in total agreement on this.

Let me expound a little more on the above ...

When using the daylighting Garry, my own observations have shown me that if you use a white backdrop, it does EXACTLY AS YOU'RE SAYING. It makes crappy stones look great!!! If you recall I posted an example of a steep/deep under the DiamondDock and it looked miserable.

Take the same stone, put a white backdrop behind it ... it gives a deceiving view. How do I know? I showed clients the same stone (not the particular one in this thread but another typical steep/deep) with a white backdrop, then afterwards would put in in a perspex tray with the neautral color of their skin behind the diamond and they couldn't believe they picked that stone!

I'm not here to make a hoopla over the diamonddock but let me say ... before it was even developed I knew the importance of using a neautral colored backdrop. Al Gilbertson has shared with me that they tried both flesh colored backgrounds as well as gray and found to get the same results. This was interesting to me because it was something I had already put into practice in my own presentations to try and present to the conumser the most accurate views we could attain in the store beyond taking them outside.

I agree 100% with what you're saying Garry however not only do I believe a consumer should be able to view fire under l.e.d's but also brightness under diffused daylight fluorescent, and if possible ... both.

Peace out,

 

[Rhino]

Before I cut out for the night ... one question Sergey or Garry ...

How does one determine a "click"? Sergey I caught your definitions ...

Ie. 1 click = 3.75 degrees etc.

3.75 degrees what? Difference from the bezel angle? Please explain.

Thanks in advance,
Jonathan

 

[michaelgem]

Rhino asks: How does one determine a "click"? Ie. 1 click = 3.75 degrees etc.
3.75 degrees what? Difference from the bezel angle? Please explain. Jonathan

In an earlier post I said:
To cut the painted crown halves, the diamondtaire sets the index to the nearest main click on his tang and then “cheats” or adjusts a small amount to either side of each main.>>> Michael

If he paints the halves 3.75 degrees in azimuth from each main facet that would be one click on a 96-index gear.

The point of confusion is that this would be 2 clicks or 7.50 degrees of painting, because the normal halves are indexed 11.25 degrees or 3clicks away from the mains. You have painted or moved the position of the top-halves two clicks or 7.5 degrees toward the mains.

This would be a major amount of painting. The halves are only 3.75 degrees or one click from the mains, so they cut in with a very light amount of grinding that removes very little material, hence the term painting.

Michael Cowing

www.acagemlab.com

 

[strmrdr]

OK, Marty you asked for it :}

I''m looking but I get tired of the ranting and agenda thrashing and do so in private.
Every once in the while I will join in on here but its rather frustrating when the signal/noise ratio is 1s/1000000n
.....
I for one hate L.E.D lighting for any gemstone and even more so for diamonds.
It a very narrow spectrum, very direct light source, it isn''t even close to any real world lighting environment.
As discussed in the other thread it is also very blue.

.....

Now as to the facts of this issue:

Fact: Gia has a wide ranging EX group that includes diamonds I wouldn''t buy.

Fact: some GIA EX diamonds are going to have have less spread than I consider optimal.

Fact: I dont have the answer to where in the real world I can go to make my diamond look just like it does in the D.D. with the diamond mounted and on my finger. If there isnt one then the lighting is total B.S.

Fact: AGS gives ags0 to a few diamonds I wouldn''t buy

Fact: AGS appears to be saying one thing but doing another with painted girdles and cut grading. Which isn''t the first time for them doing that.

Fact: Some consumers in direct comparisons outside of the vendors site have picked painted girdle diamonds over similar non-painted ones.
Some have picked the other way.

Fact: I don''t like the looks of the painted girdle diamonds Iv seen including 8*.

Fact: the average diamond sold in the US everyday is what Id consider a crap cut.

Fact: Im losing a lot of respect for a lot of people over the way they have been acting in these threads.

Fact: No one has bothered answered my orginal questions on the first page of this thread:

couple questions:
1> diamonds are often viewed at angles like that on the hand. How is that different?

2> the human head is always moving so wouldnt they pick up the other beams graphed there?

unsupported humans just dont keep their head in one position.
Also odds are that they would move for max brightness when looking at it.
From my recall of observing people looking at diamonds most would move to find the brightest look.

From a fixed camera position it would be a much bigger issue.

Fact: im rather annoyed right now
...............


Any questions?
Other than who the heck does he think he is and who made him king

 

[Garry H (Cut Nut)]

Date: 3/19/2006 10:38:09 PM
Author: Rhino
Evenin mate,

Date: 3/19/2006 8:24:23 PM
Author: Garry H (Cut Nut)
An interesting thought:

I was surprised that a retailer would use a typical dealers lighting to judge the cut quality of a diamond. Rhino uses the Geisen twin fluoro for example (I think you wrote that rhino?).

Correct. Have you ever seen this before? The lighting is calibrated 5800 degree kelvin and has a diffuser place that you can slide in and out at will. When I am demonstrating to clients the difference between brightness and fire it comes in handy. The diffuser plate in does a good job of showing brightness, take the diffuser plate out and ... well ... you can hear Earth Wind and FIRE!!!.

http://www.gesswein.com/catalog/catalog.cfm?cat=16&sub=2&subsub=3&catalog=1&CFID=657062&CFTOKEN=74146495

Using this temperature of lighting when showing clients Garry also made me realize the importance of a neautral colored background which addresses the point you bring up later in this post ...

When ever i have been buying in dealers environs - I never make decisions in that lighting & I am asking myself why? (perhaps instinctively - perhaps because it disagreed with my Ideal-scope / FS observations - I dont know when or why I stopped or changed).

Sergey has shown now that this is really bad, and shown why. I always knew that looking at inclusions with backlight thru the diamond was bad news for cut grading - even though I have seen countless thousands of merchants, graders and appraiser students do it. And a typical dealer has a big white pad on the desk just to make the environment worse.

TOTALLY AGREE!

I think back to some of my debates with Brad and Jan - and it is clear now why they believe what they believe - I thought at the time that they were simply allowing back light to enter the pavilion because the way they took their photo''s - but actually they too probably use strong desk liights!!!

How do we get the trade to change to using consumer type lighting?
How do we stop this stoopid usage of LED lamps sitting on desks so people can see the fire in a diamond?

I think you mean fire under LED''s? Most dealers have non-diffused fluorescent tube lighting like this.
http://www.gesswein.com/catalog/catalog.cfm?cat=16&sub=1&subsub=6&catalog=1&CFID=657062&CFTOKEN=74146495

The problem with dealer lighting: Daylight fluorescent with a white/bright paper backdrop is on the desks of most dealers and making crapola look good. I think we are in total agreement on this.

Let me expound a little more on the above ...

When using the daylighting Garry, my own observations have shown me that if you use a white backdrop, it does EXACTLY AS YOU''RE SAYING. It makes crappy stones look great!!! If you recall I posted an example of a steep/deep under the DiamondDock and it looked miserable.

Take the same stone, put a white backdrop behind it ... it gives a deceiving view. How do I know? I showed clients the same stone (not the particular one in this thread but another typical steep/deep) with a white backdrop, then afterwards would put in in a perspex tray with the neautral color of their skin behind the diamond and they couldn''t believe they picked that stone!

I''m not here to make a hoopla over the diamonddock but let me say ... before it was even developed I knew the importance of using a neautral colored backdrop. Al Gilbertson has shared with me that they tried both flesh colored backgrounds as well as gray and found to get the same results. This was interesting to me because it was something I had already put into practice in my own presentations to try and present to the conumser the most accurate views we could attain in the store beyond taking them outside.

I agree 100% with what you''re saying Garry however not only do I believe a consumer should be able to view fire under l.e.d''s but also brightness under diffused daylight fluorescent, and if possible ... both.

Peace out,

Have you just got back from a sales training conference Rhino?

I 100% agree with but......

I am not saying that the LED desk lights being sold to lots of retailers and used in DD are good - I am saying they should be destroyed on sight.

I have never agreed with anyone who says high colored temp fluoro''s have any use anywhere in the jewellery industry - for any purpose from red reflectors to color grading and especially for cut grading.

But mostly I disagree with using any light that is closer than 2 meters from a diamond for visual cut grading.

 

[Garry H (Cut Nut)]

Date: 3/19/2006 10:42:17 PM
Author: Rhino
Before I cut out for the night ... one question Sergey or Garry ...

How does one determine a ''click''? Sergey I caught your definitions ...

Ie. 1 click = 3.75 degrees etc.

3.75 degrees what? Difference from the bezel angle? Please explain.

Thanks in advance,
Jonathan

Jonathon I sent you an email with links to 2 journal articles by Bruce Harding and Peter Yantzer that explained this info

 

[Garry H (Cut Nut)]

Date: 3/19/2006 11:52:52 PM
Author: strmrdr
OK, Marty you asked for it :}

I''m looking but I get tired of the ranting and agenda thrashing and do so in private.
Every once in the while I will join in on here but its rather frustrating when the signal/noise ratio is 1s/1000000n
.....
I for one hate L.E.D lighting for any gemstone and even more so for diamonds.
It a very narrow spectrum, very direct light source, it isn''t even close to any real world lighting environment.
As discussed in the other thread it is also very blue.

agreed.....

Now as to the facts of this issue:

Fact: Gia has a wide ranging EX group that includes diamonds I wouldn''t buy.

Fact: some GIA EX diamonds are going to have have less spread than I consider optimal.You and me both Storm - GIA certainly has done nothing to take the guess work out of diamond shopping - Michale and all you other GIA fans - I bet you would not buy your wife a GIA graded diamond with Excellent Cut on their say so without further checking the paper and or the stone!!!

Fact: I dont have the answer to where in the real world I can go to make my diamond look just like it does in the D.D. with the diamond mounted and on my finger. If there isnt one then the lighting is total B.S.

Fact: AGS gives ags0 to a few diamonds I wouldn''t buy I would feel 90% safe with an AGS stone sight unseen, and 20-30% safe with a GIA

Fact: AGS appears to be saying one thing but doing another with painted girdles and cut grading. Which isn''t the first time for them doing that.How so? I have heard Michael say this - but believe 8* send their stones to AGS now, and not GIA - and i believe Brian sends his painted stones to AGS - confirm please brian / John?

Fact: Some consumers in direct comparisons outside of the vendors site have picked painted girdle diamonds over similar non-painted ones.
Some have picked the other way.

Fact: I don''t like the looks of the painted girdle diamonds Iv seen including 8*.

Fact: the average diamond sold in the US everyday is what Id consider a crap cut.

Fact: Im losing a lot of respect for a lot of people over the way they have been acting in these threads.

Fact: No one has bothered answered my orginal questions on the first page of this thread:

couple questions:
1> diamonds are often viewed at angles like that on the hand. How is that different?

2> the human head is always moving so wouldnt they pick up the other beams graphed there?

unsupported humans just dont keep their head in one position.
Also odds are that they would move for max brightness when looking at it.
From my recall of observing people looking at diamonds most would move to find the brightest look.

From a fixed camera position it would be a much bigger issue.

Fact: im rather annoyed right now
...............


Any questions?
Other than who the heck does he think he is and who made him king

 

[dhog]

so garry: do you think that a person could
market a micro sized led,that would mount
to the back of the tray to really
enhance the look, remotely cotrolled of course ,powered by
a small watch battery

 

[strmrdr]

I said:

"Fact: AGS appears to be saying one thing but doing another with painted girdles and cut grading. Which isn''t the first time for them doing that.

Gary Said,

How so? I have heard Michael say this - but believe 8* send their stones to AGS now, and not GIA - and i believe Brian sends his painted stones to AGS - confirm please brian / John?"

They told Michael they were down grading them when they arent as shown by the cert I posted earlier.

 

[dhog]

Date: 3/20/2006 12:49:50 AM
Author: strmrdr
I said:


''Fact: AGS appears to be saying one thing but doing another with painted girdles and cut grading. Which isn''t the first time for them doing that.


Gary Said,


How so? I have heard Michael say this - but believe 8* send their stones to AGS now, and not GIA - and i believe Brian sends his painted stones to AGS - confirm please brian / John?''


They told Michael they were down grading them when they arent as shown by the cert I posted earlier.

its a good thing I took your advise earlier and
tried to keep this thread on track.

at least now us consumers know what side of
the fence your on.

as a consumer for other consumers I am here
to pursue what is right for consumers, not a bunch
of hyped up light box that is designed to sell more
crappy stones if you will.

I have nothing to lose in this battle so if you
want some more hard facts: feel free to respond

 

[Rhino]

Dam this forum... gives me brainfarts.

Date: 3/19/2006 10:25:00 PM
Author: Shay37

A lot of the jewelry stores around here offer either GIA or EGL. Most do not offer diamonds with AGS certs. So the one cert with cut info for the longest time has been pretty unavailable by and large to Joe Q Public. This is at least a step forward for most people not doing research on line to be able to know that cut is important. It''s not a complete step by any means, but it''s a definite start. Now, if we could just outlaw jeweler''s lights for the making of the dogs into the dolls at least until you pay and get them home. Ahhh, but that''s a topic for another day.

Keep it coming guys. I''m enjoying the byplay.

shay

Hi Shay...

Some more very good news for the types of consumers you speak of. While I do not take sides either way (GIA or AGS), I have to say that even with the minor issues of rounding, with the proportion data provided on the new GIA reports one can more accurately determine diamond appearance since they have the inclusion of both lower half and star measurements. That has been my biggest gripe over the years regardings Sarin''s and AGS Reports. Lower half facets, IMO have the 2nd most important impact on the face up appearance of a round brilliant cut diamond (pavilion mains being the first). Mike Cowing pointed this out to me in a recent discussion. Even with the 2.5% rounding of the lower halves that GIA is doing, at least one can produce a fairly accurate DiamCalc model with this additional information that will much better serve the consumer in the end. If you recall in the past when one would post Sarin data and I''d shrae graphics of what the stone would potentially look like, the graphic covered an "array" of appearances. Attached is a graphic that I have posted in the past showing this array. Next post I''ll show you the largest variations in appearance included in GIA''s rounding.

 

[JohnQuixote]

Date: 3/20/2006 12:41:35 AM
Author: Garry H (Cut Nut)

Fact: AGS gives ags0 to a few diamonds I wouldn't buy I would feel 90% safe with an AGS stone sight unseen, and 20-30% safe with a GIA

Fact: AGS appears to be saying one thing but doing another with painted girdles and cut grading. Which isn't the first time for them doing that.How so? I have heard Michael say this - but believe 8* send their stones to AGS now, and not GIA - and i believe Brian sends his painted stones to AGS - confirm please brian / John?

Garry - we’ve been submitting all ‘A Cut Above’, traditional and painted, to the AGS for the last 7 years. Before that time we had submitted to both labs, but clients viewed the DQD as the top shelf document due to the proportions details and high Ideal standards.

Please note, since the launch of 0 light performance these diamonds have been graded under the new system and continue receiving the Ideal grade. It’s nothing new. We have two styles: Classic (traditional brillianteering) and New Line (painted brillianteering). Painting was never a fuss, as it has never been seen as deleterious. Thousands of clients view the styles side by side and consider them equal in beauty.

Digging/painting is required in all brillianteering techniques – it just may not be overly harsh. What level of digging should be penalized and what level of ‘painting’ constitutes ‘painting?’ Brillianteering technique is a matter of common sense. Used correctly the craftsman can apply these techniques to cover many faults or errors and still complete a cut stone complying with the requirements of the AGS - or GIA.

 

[JohnQuixote]

Date: 3/19/2006 10:06:53 PM
Author: Rhino

Date: 3/19/2006 8:14:59 PM
Author: JohnQuixote

Agreed. There are combinations of steep a bit outside of AGS' paradigms or shallow a bit outside GIA's paradigms that will appeal to people. I think we're fine with that. But don't you agree that most people would not prefer a 1.28 with the face-up spread of a 1.16 (for example)...if they were aware that this was the case?

Absolutely John and excellent point.

While certain optical properties may boil down to peronal preference, if you take the fringes of each cut system regarding depth vs the typical goodies the conneisuers look out for in places like here ... a 60.x or 61.x depth will always win out over a 62.7 or 63%

Correct. Jewelers of repute will protect their clients; any of us on this channel surely will - and good appraisers are a second line of defense. But there are outlets that will sell poor performers/hidden weight and could use the EX pedigree to support it in a manner you or I never would.

Actually I hope you (and friends at GIA) understand the statement Brian made, which started these discussions, doesn't pertain to sellers or buyers populating the PS community: There is a much larger picture involving upstream manufacture, which Brian is quite in touch with. His concerns lie with mass marketers who take advantage of that upper window of steep/deep - wouldn't you agree that the potential for abuse is there (heavy cutting)?

 

[Rhino]

Disregard that last graphic Shay. I used the same lighting in the next 2 examples to avoid confusion.

This graphic here depicts what a person *could get* with no lower half or star informtion. Note the difference in appearance between these 2. Any expert here will tell you ... there is a notable difference in appearance. One that I believe any layman would be able to see. I altered the lower half length from 75% to 85%. Ideal standards in both grading systems.

 

[Rhino]

Here's same diamond model, same lighting using GIA's min/max rounding.

These images are blown up big time to show detail, however if you scale these down to size you'll see why I don't consider GIA's rounding a bad thing. In fact it gives consumers who have access to new GIA Reports a much better idea of what kind of appearance they can expect.

Just 2 things need to be kept in mind that are not included in those images.

1. girdle cutting
2. The model in DiamCalc assumes "ideal" optical symmetry whereas the majority of diamonds on the market do not have symmetry that perfect.

Neat eh?

 

[dhog]

Date: 3/20/2006 1:31:17 AM
Author: Rhino
Dam this forum... gives me brainfarts.

is this a classic : type of stone or are
these theories leading up to the possibility that
maybe in the future a cutter could produce the ultimate
painted stone for us consumers to consume

 

[Rhino]

Date: 3/19/2006 11:48:53 PM
Author: michaelgem

Rhino asks: How does one determine a ''click''? Ie. 1 click = 3.75 degrees etc.
3.75 degrees what? Difference from the bezel angle? Please explain. Jonathan

In an earlier post I said: <<<BTW, for those reading who may not be aware, one click is 3.75 degrees only in a 96-index gear, which is typically used on a faceting machine to cut colored stones, not diamonds. The typical “tang” used in diamond cutting only has clicks at the normal mains and halves indexes. The normal halves indexes are 11.25 degrees away from the main indexes.

To cut the painted crown halves, the diamondtaire sets the index to the nearest main click on his tang and then “cheats” or adjusts a small amount to either side of each main.>>> Michael

If he paints the halves 3.75 degrees in azimuth from each main facet that would be one click on a 96-index gear.

The point of confusion is that this would be 2 clicks or 7.50 degrees of painting, because the normal halves are indexed 11.25 degrees or 3clicks away from the mains. You have painted or moved the position of the top-halves two clicks or 7.5 degrees toward the mains.

This would be a major amount of painting. The halves are only 3.75 degrees or one click from the mains, so they cut in with a very light amount of grinding that removes very little material, hence the term painting.

Michael Cowing

www.acagemlab.com

Thanks for clarifying Mike. Wowza ... so a 2 click painting IS alot of painting considering there are only 3 clicks between bezel and half eh?

Now here''s a question for ya. How can one look at a DC model and determine whether 1 or 2 clicks were used in the painting. The gem file I had posted of a 1.196ct diamond Sergey mentioned was between 1 and 2 clicks. It is possible to paint between 1 and 2 teeth on the gears?

Sergey... what do you consider to be going to far? I am interested in your thoughts on this.

 

[JohnQuixote]

I am a great fan of minor facets too. Even before I entered the trade I couldn't believe they weren't being taken into consideration in existing metrics. GIA stepped up to the plate by studying/including them. AGS now accounts for them in their light performance metric (Note however that AGS still extends the old DQD as an option, because some factories cannot yet meet the rigorous standards of the new light performance metric...those old DQDs take no minor facet info into account).

It's weird to suddenly be on this size of the accuracy argument with Rhino, who was the first on his block to own a shiny new Helium scanner. I applaud GIA for taking minors into account but the rounding stuff (particularly with minors: 5% and crown angle: 0.5 degree) is a shame to me.

Example: These three diamonds would be considered exactly the same by GIA (stars & lower halves within 5%). Not a 'train smash' as one might say, but certainly not as accurate as we're capable of being.

 

[Rhino]

Date: 3/20/2006 12:26:02 AM
Author: Garry H (Cut Nut)

Have you just got back from a sales training conference Rhino?

LOL! NO!

Date: 3/20/2006 12:26:02 AM
Author: Garry H (Cut Nut)

I am not saying that the LED desk lights being sold to lots of retailers and used in DD are good - I am saying they should be destroyed on sight.

I have never agreed with anyone who says high colored temp fluoro's have any use anywhere in the jewellery industry - for any purpose from red reflectors to color grading and especially for cut grading.

But mostly I disagree with using any light that is closer than 2 meters from a diamond for visual cut grading.

Question 1: What lighting environment do you suggest a consumer view fire in when visiting their local jewelry store?
Question 2: What lighting environment do you suggest a consumer view brightness in when visiting their local jewelry store?

Here's another question to ponder.

If bright lighting with white backgrounds make steep deeps look good ... reverse the roles for a sec mate. What would be an equally worse mistake?

What I'm getting at here is this. Think of common real world everyday engagement ring conditions. Would you say most of the consumers buying engagement rings are having their diamonds mounted in prongs or bezels?

If prongs, now think about this ... is the pavilion covered with no light being allowed from behind?

Would you say the background is bright white (such as the white paper under a desk lamp in most diamantaires offices), inky black (like the background you use to compare the cz's) or perhaps a more neautral color (such as metal or skin underneath the diamond)?

There is however a good time to use a black background to make a judgement however if you do want to reflect real world conditions. What type of setting completely encases the pavilion and prevents any light or color from being transmitted through the top?

Peace,

 

[Serg]

Date: 3/20/2006 2:17:46 AM
Author: Rhino

Date: 3/19/2006 11:48:53 PM
Author: michaelgem


Rhino asks: How does one determine a ''click''? Ie. 1 click = 3.75 degrees etc.
3.75 degrees what? Difference from the bezel angle? Please explain. Jonathan

In an earlier post I said: <<<BTW, for those reading who may not be aware, one click is 3.75 degrees only in a 96-index gear, which is typically used on a faceting machine to cut colored stones, not diamonds. The typical “tang” used in diamond cutting only has clicks at the normal mains and halves indexes. The normal halves indexes are 11.25 degrees away from the main indexes.

To cut the painted crown halves, the diamondtaire sets the index to the nearest main click on his tang and then “cheats” or adjusts a small amount to either side of each main.>>> Michael

If he paints the halves 3.75 degrees in azimuth from each main facet that would be one click on a 96-index gear.

The point of confusion is that this would be 2 clicks or 7.50 degrees of painting, because the normal halves are indexed 11.25 degrees or 3clicks away from the mains. You have painted or moved the position of the top-halves two clicks or 7.5 degrees toward the mains.

This would be a major amount of painting. The halves are only 3.75 degrees or one click from the mains, so they cut in with a very light amount of grinding that removes very little material, hence the term painting.

Michael Cowing

www.acagemlab.com

Thanks for clarifying Mike. Wowza ... so a 2 click painting IS alot of painting considering there are only 3 clicks between bezel and half eh?

Now here''s a question for ya. How can one look at a DC model and determine whether 1 or 2 clicks were used in the painting. The gem file I had posted of a 1.196ct diamond Sergey mentioned was between 1 and 2 clicks. It is possible to paint between 1 and 2 teeth on the gears?

Sergey... what do you consider to be going to far? I am interested in your thoughts on this.

re: It is possible to paint between 1 and 2 teeth on the gears?

1) Cutters can use Other index gear. ( for example like for Pear cut)
2) Cutters can use "analog" index too.

I think Cutters can control near 1 degree for index now ( may be even 0.5 degree)

 

[Rhino]

Date: 3/20/2006 1:38:27 AM
Author: JohnQuixote

Date: 3/19/2006 10:06:53 PM
Author: Rhino

Date: 3/19/2006 8:14:59 PM
Author: JohnQuixote

Agreed. There are combinations of steep a bit outside of AGS' paradigms or shallow a bit outside GIA's paradigms that will appeal to people. I think we're fine with that. But don't you agree that most people would not prefer a 1.28 with the face-up spread of a 1.16 (for example)...if they were aware that this was the case?

Absolutely John and excellent point.

While certain optical properties may boil down to peronal preference, if you take the fringes of each cut system regarding depth vs the typical goodies the conneisuers look out for in places like here ... a 60.x or 61.x depth will always win out over a 62.7 or 63%

Correct. Jewelers of repute will protect their clients; any of us on this channel surely will - and good appraisers are a second line of defense. But there are outlets that will sell poor performers/hidden weight and could use the EX pedigree to support it in a manner you or I never would.

Actually I hope you (and friends at GIA) understand the statement Brian made, which started these discussions, doesn't pertain to sellers or buyers populating the PS community: There is a much larger picture involving upstream manufacture, which Brian is quite in touch with. His concerns lie with mass marketers who take advantage of that upper window of steep/deep - wouldn't you agree that the potential for abuse is there (heavy cutting)?

Absolutely John. My point however was that if we're going to level criticisms and accusations against GIA for allowing up to a 63% depth, no mention will be made of allowing 62.8? I am for honest critique, I just don't like to see it aimed squarely at one lab when the other is just .2% away. That's all. I have my own criticisms about both systems and were I to develop a cut grading system of my own would consist of different standards. I do realize however that my grading is not practical for the industry as a whole and I would say ... neither would Brians. We're both too anal.

Peace,

 

[Rhino]

Hi John,

What are the lower half lengths (or depths in DC) of each of those stones? I also note a slightly shallow pavilion angle. Curious. The reason why I ask about the pavilion angles is becuase if those are shallow enough to cause an overdarkening of the mains, that would disqualify a stone from the top grade as well.

Edited to add: Wouldn't you agree that GIA including this information on reports, is better than not having it at all?

 

[Serg]

re:I too am interested in garnering results for this as well. I think I know some manufacturers (MSS?) who are up for the task. Matter of fact, Paul Slegers, if we give him a model can basically duplicate it. I recently had a feww new stones cut by him for experimentation and research on a new line we are considering to stock and he did a rather remarkable job of duplicating the DiamCalc model I forwarded to him. If you'd like to compare his results with the model I sent I'll show you the comparisons in email. I would be willing to put up some cash as well for this and will help sell the test stones once all the testing is complete by whomever you have participate.

Rhino,

Please send to me original DC model and mmd file from Helium.

Paul has not Helium. For me much more easy work with big Indian manufactures which have Helium. ( More possibility for selection and more cheap)

 

[Rhino]

Date: 3/20/2006 2:31:27 AM
Author: Serg

re: It is possible to paint between 1 and 2 teeth on the gears?

1) Cutters can use Other index gear. ( for example like for Pear cut)
2) Cutters can use ''analog'' index too.

I think Cutters can control near 1 degree for index now ( may be even 0.5 degree)

Thanks for sharing this with me Sergey. I wasn''t aware of how close or accurate a cutter can control these features. How about my last questoin? At how many degrees do you feel the painting becomes an issue? Ie ... your personal "no go" zone? 4 degrees? 5, 6? I am curious to know your personal thoughts on this if you don''t mind sharing.

Kind regards,

 

[Serg]

re:The bigger the better - say 3/4ct - in a perfect world the stones are all either the same diameter and different weights - but all in the same weight / price grid - or the same diameter but different weights. This is what i tried to do with my Diamond Dock study.


Garry, I prefer same diameter for all diamonds. 6mm<>3/4 ct

 

[Rhino]

I''ll have this out to ya Tuesday morning when I get up to the lab.