41 degree pavillion angle

[whatmeworry]

Date: 7/14/2007 2:16:40 PM
Author: Cehrabehra

Date: 7/14/2007 1:50:29 PM
Author: Rhino
does this AGS graded 1.90ct H VS1 ideal cut diamond appear to be compromised in any way?

I just wanted to say, this is one very beautiful diamond Jon

There are beautiful diamonds on the fringes... and there are beautiful diamonds beyond the fringes. Every time the aset poster is shown with the 10k of images I think less of ''there is *the* zone'' and more of, ''I really would love to see some of the diamonds out on these other islands.''

I''m with you. I''d like to see what the map looks like when the soil is composed of 80% brightness and 20% fire or vice versa. You know, Garry''s BIC/FIC islands. But that''s for another thread.

 

[michaelgem]

Date: 7/14/2007 7:07:52 AM
Author: Pyramid
Is a 34/41 considered a shallow/deep, I thought shallow was more like 32 and under?

For crying out loud. 34/41 is smack dab in the middle of the Ideal sweet spot in most grading systems and for most Ideal cutting houses.

As far as there being some transition between 40.9 and 41 from good to bad, or as Wink said "41 is at the edge of the cliff" is just not supported by the evidence either from AGS, GIA, MSU or me.

The evidence I discuss in my article does show that as you increase the pavilion angle from Tolkowsky''s 40.75 to 41.4, you should reduce the crown angle from 34.5 somewhat along the "axis of Ideal" to maintain Ideal, Excellent or Ags Ideal 0 light performance.

Implying that there is a cliff at 41 degrees when the GIA Excellent and AGS Ideal 0 pavilion angles go to 41.8 for a 56-57% table lacks support from either AGS or GIA.

My latest article in the Journal of Gemmology speaks directly to this. It explores the center of the sweet spot in Ideal round brilliant diamond cutting in all the seven dimensions currently being used to define the standard round brilliant (standard indexing, no painting or digging).
The center of the AGS Ideal and the GIA Excellent sweet spots for pavilion, crown and table are closest to a 41 pavilion angle, 34 crown angle, and a 56% table, and not Tolkowsky’s angles of 40.75, 34.5 and 53%.

Looking at the posted specifications, this 1.90ct is spot on as a superideal.

I found that the center of the 7-dimensional sweet spot for pavilion angle for Ideal or Excellent cutting was 41.2 for GIA and 41.1 for AGS. They agree within 0.1 on the pavilion angle center and within 0.25 on the corresponding best crown angle center of 34.

This sweet spot center of 41 and 34 agrees with my investigations based upon direct assessment of the diamond''s optical performance in typical illumination circumstances. The sweet spot center is also in agreement with the teaching of diamond cutters and diamond cutting institutions.

“From the 1970’s the Institute for Technical Training in the Antwerp province of Belgium taught angle combinations of 41 and 34 - 34.2 (personal communication with , Dirk Verbiest, cutter of ideals and 1977 graduate diamond cutter.) In the same time frame, but a continent away in Johannesburg, South Africa, the Katz Diamond Cutting Factory was teaching its apprentices to cut the Ideal Round Brilliant to a 41 pavilion main angle and a 33 to 35 crown main angle (pers. comm., P. Van Emmenis, a notable cutter of Ideals who recently was hired to give a course in diamond cutting to AGSL)”

So if you want to split hairs, and we all do, I can say with confidence and a large body of evidence, that this 1.90ct with a 41 pavilion in combination with the appropriate crown angle close to 34 is equal to and, in a hair splitting but observable way, superior to Tolkowsky’s theoretical 40.75 and 34.5.

You will not find a super ideal cut diamond with better beauty/ light perforrmance. You can take that to the bank.

Ideal regards,

Michael

 

[junior35]

Date: 7/13/2007 1:48:41 PM
Author: BrianTheCutter

With respect to the analysts, as a diamond cutter my grandfather and father taught me the only reason to go over 40.9 is to either darken the stone or hold more weight. It is a fact. This is not about labs or beauty it is about dollars and cents.

Blocking the pavilion at 41 instead of 40.75 can eliminate +/- 1% of waste in sawable octahedron. In a 100,000 carat production that’s 1000 cts or more! This is $4,500,000.00 additional profit at an avg wholesale price of $4500/ct. It is no wonder so many manufacturers are on record saying 41 is fine…

I disagree because it is a perilous threshold for color entrapment. Sorry guys, but this is something the labs and theorists do not pay heed to. Go much steeper or shallower than Tolkowsky’s 40.75 and you increase the intensity of color in a stone. It’s unavoidable. I’ve seen it since the days when my grandfather was teaching me. Once you’re over 40.9 in sizes over half a carat this effect kicks into place and the stone darkens further as you increase the angle. Table reflection becomes bigger as pavilion angle increases and can exaggerate the effect. Crowns may be adjusted to maximize entrapment but the pavilion is what is key - which is why fancy-colored stones are cut deep or shallow to intensify their color.

I appreciate John Pollard and others talking about lab grading but it’s simply not useful in this situation. Nothing but live analysis will show color entrapment. Not theses, not photos, not videos, nothing but human eyes. The AGS ray-trace does not pick up color entrapment. GIA includes combos at the steep end of EX that retain weight, entrap color and produce poor looking stones with small spread (no one will deny this). This has allowed manufacturers to push limits at the expense of beauty.

As margins shrink and rough prices climb cutters are pressed to save as much weight as possible. This is the reason you find pavilions creeping up and fewer 40.75 angles. It’s simply not as profitable to produce them in some situations (by the way, 1-5ct goods in collection colors have gone up in price again). 41 combinations are close enough to ‘make the grade’ at labs and they are better money-makers for cutters. My family has always aimed for Tolkowsky’s pavilion. We could make extra money cutting deeper but that’s not what it’s about – it’s about striving for the best of the best.

Do not misunderstand. I’m speaking as a diamond cutter (and some may say a snob). Combinations at 41 can be beautiful and we don’t tell people not to buy them. In fact, we recommend them to clients seeking to be cost-effective, but they must be inspected firsthand because labs are blind to this issue. Well-cut diamonds can be beautiful at the threshold, but as an expert diamond cutter I do not approve of the reason factories are aiming high and pushing limits. I learned these things at the wheel long before the labs ever graded cut.

Sadly, I expect to see more manufacturers cutting steeper & deeper because they are cutting to make money, not for the most optimum performance. Color entrapment and economics are diamond cutting facts.

With all due respect,since you are throwing big numbers around,I thought I would put these into perspective.
I assume you are talking about a yearly production so:
100,000 carats polished diamonds would come from aproximately 212,000 carats rough (assuming 47% yield)
And since you are talking about an average price of $4500/carat that means that you are talking 3-4 carat rough at approx $2000 per carat.
So in effect what you are referring to is a manufacturer who polishes 21200 carats per month(normal sight cycle) of 3-4 carat rough at $2000 per carat,yes?
That''s $42,400,000 production per month!Wow
And who exactly is this manufacturer?

 

[pyramid]

The reason I wrote about the crown being shallow was because of the images BriantheCutter put up for the shallow/deep stone, would the 34/41 be considered this or is that more a 32 and under crown. Does any of the experts think the crown on the 34 would not look as nice from a profile view because it is shallower?

 

[JohnQuixote]

 

[strmrdr]

 

[WorkingHardforSmallRewards]

Date: 7/14/2007 6:40:42 PM
Author: Pyramid
The reason I wrote about the crown being shallow was because of the images BriantheCutter put up for the shallow/deep stone, would the 34/41 be considered this or is that more a 32 and under crown. Does any of the experts think the crown on the 34 would not look as nice from a profile view because it is shallower?

Hey Pyramid, I am glad that I have decided to stay out of this thread now..at least wherein all that mess going on up above is concerned--I had anticipated this after reading BC's post though actually, hopefully things will get smoothed out.Oh, and MG, I love that "for crying out loud" I may not have ever met you or heard your voice, but I can hear THAT voice loud and clear

Now to the following, if I have misunderstood I will be terribly embarrassed. you can laugh at me if I did.
But, Pyramid, what you are asking here isn't really a scientific question is it, and thus not one that these men are really very UNIQUELY qualified to answer but should probably be directed more toward the average consumer than the distributor? True, they do see alot of examples, but I don't think that has anything at all to do with their taste in profile views vs your own.

Couldn't you go out to a some jewelry stores and look at diamonds with 34degree crown angles and similar mm height and width? Then you could actually see them in settings and sortof ignore the total depth element and decide how you feel about that % height and that degree angle from a profile view, bringing some sortof mm measuring device with you to check the thickness of the prongs in question of coruse. after all, the heart of the question is that the lower angle will bring the table down closer to the level of the prongs right? giving it a somewhat flatter appearance? I really doubt it would be a problem from what I have seen, but that is really a personal question that should be easily cured by going to some local jewelers and judging the height of similar dimension, percent and, degree crowns and just consider it independent of the total depth. I imagine that would suffice well enough to judge specifically what you are looking at, though with some ingenuity you could probably create life size to scale models out paper at home and set them into rings. but that would be way too complicated for me (Actually, I sortof did that during my hunt when considering sizes..it was difficult and very inaccurate...hard to cut a piece of paper .3mm wider..lol. Good times. They could also be 3:1 if that would help to give an ideal of the difference.)


As to my own diamond, I have a 34.8 which is going to be much lower than yours for the sake it is a smaller diamond and thus the % height yield is greater in your larger diamond. I feel that it is a fantastic height to stand up, I wouldn't mind it being a little higher though, but it has a very elegant look, to my eyes anyway.

Your diamond selection looks amazing to me.If you are happy with the SPREAD of your diamond then that would negate the importance of one of Brian's points, and if you are happy with the face up appearance color of your diamond then that would negate the second of his points. and if it isn't dark then it isn't dark, and given all of the research we have both been reading about I think we can pretty conclusivly say that a 34/41 should not be dark. After doing my own studying at the same time as you, on here and elsewhere, your diamond looks to be absolutely incredibly well cut to me so from me and my idiot consumer point of view I give you a Green light for whatever that is worth.

 

[pyramid]

Date: 7/12/2007 7:56:42 PM
Author: He Scores


Once the bottom main angles go over 41 degrees the center of the stone ( between the table reflection around the culet and the stars) begins to darken.

The greater the error over 40.75, the more evident it is to the naked eye.

Since most conumers don''t have the redfield images to compare to when they''re shopping in a store.


Bill Bray
Diamond Cutter

This is the Idealscope image, does it show any darkness around the culet between the stars?

 

[pyramid]

Thanks WorkingHard

I need not ask any jewellers around where I live for the crown height they just would not know and there are very few GIA certificates and I have never seen an AGS one, it is mostly HRD or IGI or there is a certificate can't remember the name now from a lab in Birmingham, a city in England.

I do have smaller diamonds with crown heights which look higher than this one but I am not sure if I like it better or not, I think I do like the higher crown, however I know it is a personal preference or not but I was just wondering what the experts think.

I am trying to stay out of this thread to see what they are all saying, because really I am not qualified to have an opinion upon it. However it does help make up your mind when you hear different sides. I am reading though.

I have read about crowns being too tall being more susceptible to chipping but that may be like 36 or 37 degrees or something, I have read on some sites that the diamond should not have a high crown, I think that was on a Belgium site, I have read that you should look at the diamond and divide it in three from the profile and it should be one third crown and two thirds pavillion, don't know what it is meant to be and these are all just opinions from lay people trying to work it out.

I think the experts have all really given their opinions and their minds are obviously into what they believe so it is really just a matter of making up my mind about it all.

I have got the diamond now and I honestly see nothing wrong with the colour, I can see it is an H and not a F and I see it more coloured than a G which I have but this is a much smaller diamond. I am very colour sensitive and clarity sensitive and I can see a difference in colourless diamonds but this H is white enough, I can appreciate them all. So I am happy with the colour. I can't see any colour entrapment although I am not sure if that means like a body of colour like someone else was seeing in the centre of their J colour diamond or does it mean the same colour throughout the stone, but the colour does not bother me one bit. With any diamond the clarity would bother me more than the colour which is why I chose VS1 and would not go below that, silly for some but that is what is right for me. I know I spent too long worried about feathers in previous diamonds I have that I am more picky than I should be on that one but I am happy to pay for it. I am happy with the spread, it is listed as -1% on Pricescope and both Whiteflash and GoodoldGold have many listed at -2 and -3% as well as -1%, 0% and 1%. I am not sure about the darkening between the table reflection and the stars, I have tried to look but it is midnight here so with night lights I am not sure if I can see anything, I will have to look in daylight. I think it is more the mind clean thing that some are against 41pavillion and the profile view from the side and I am not sure about the fire and scintillation because of the HCA score, like there is a lot but not sure yet how much there should be. I have not had any sunlight and not really looked under different lights yet. I will not be wearing the ring outside unless I have decided I am keeping it.

 

[strmrdr]

entrapped light similar to a barion cut with a 34 degree crown angle.
Where the light bounces back and forth around the girdle area traveling thru a lot of material picking up color.
.
.
.
.
it took 41.6 degrees before it was to any great degree more of it than 40.9
At 41.6 it shot up a lot.
So in my opinion the angle of entrapment for this combo I modeled is 41.6 degrees not 41.

 

[strmrdr]

for a 34.8 crown it again goes off a cliff at 41.6

 

[psadmin]

Ladies and Gentlemen,

Please stick to helping Pyramid with his question not each other’s opinions.

Thank you for your help,
Andrey
PS Admin

 

[strmrdr]

put a 7% girdle on it to minic a barion cut a bit and it goes off the cliff at 41.3

 

[JohnQuixote]

Date: 7/14/2007 7:02:18 PM
Author: strmrdr

Date: 7/14/2007 6:49:05 PM
Author: JohnQuixote

In any event, this was not an attack on your diamond Rhino. You mobilized as if you were being personally assaulted. It's not about you and I hope you’ll step back, relax, crack a frosty beverage and enjoy your day.

You do realise that the diamond that Pyramid who started this thread is worried about is this one as Jon posted a few posts back?

We all do now. It's become a bit silly.

Question: Can a car take that corner at 60 mph?
Topic: We wouldn't advise it, some cars will skid out at that threshold.
Specific: I disagree, that corner is perfectly safe.
Topic: For some it can be, but many cars have skidded out at that mph.
Specific:You're wrong!My car never skids out! (shows his car not skidding out).
Topic: Ok.

(ps: some cars still skid out)

I don’t know how much more I can stress Brian’s comments are not about a specific diamond.
Is this going to be a topic or diamond-specific thread?

 

[strmrdr]

Pyramid, We have known each other here a long time.
Iv seen 41/34 combo stones in person that were absolutely stunning.
Playing around with DC shows that the angle of entrapment may be higher than thought.
Jon who you have known a long time has seen the stone and rates it high enough to attach his "brand" too it and sell it.
I dont know what else to tell ya.

 

[pyramid]

Date: 7/14/2007 7:56:06 PM
Author: PS Admin

Ladies and Gentlemen,

Please stick to helping Pyramid with his question not each other’s opinions.

Thank you for your help,
Andrey
PS Admin

I am a her

, thank you for that though Andrey. I know I have to make up my own mind so the opinions are interesting to me.

 

[strmrdr]

Date: 7/14/2007 8:00:47 PM
Author: JohnQuixote

Date: 7/14/2007 7:02:18 PM
Author: strmrdr

Date: 7/14/2007 6:49:05 PM
Author: JohnQuixote

In any event, this was not an attack on your diamond Rhino. You mobilized as if you were being personally assaulted. It''s not about you and I hope you’ll step back, relax, crack a frosty beverage and enjoy your day.

You do realise that the diamond that Pyramid who started this thread is worried about is this one as Jon posted a few posts back?

We all do now. It''s become a bit silly.

Question: Can a car take that corner at 60 mph?
Topic: We wouldn''t advise it, some cars will skid out at that threshold.
Specific: I disagree, that corner is perfectly safe.
Topic: For some it can be, but many cars have skidded out at that mph.
Specific:You''re wrong!My car never skids out! (shows his car not skidding out).
Topic: Ok.

(ps: some cars still skid out)

I don’t know how much more I can stress Brian’s comments are not about a specific diamond.
Is this going to be a topic or diamond-specific thread?

nice anology...
As far as Im concerned I have done all I can to help Pyramid so im out.
If you want to discuss entrapment at a later date then that''s kewl.

 

[psadmin]

Date: 7/14/2007 8:04:22 PM
Author: Pyramid

Date: 7/14/2007 7:56:06 PM
Author: PS Admin

Ladies and Gentlemen,

Please stick to helping Pyramid with his question not each other’s opinions.

Thank you for your help,
Andrey
PS Admin

I am a her

, thank you for that though Andrey. I know I have to make up my own mind so the opinions are interesting to me.

OOPS

Pardon me.

I am all for opinions but not when they are not on the actual topic at hand.

Andrey
PS Admin

 

[pyramid]

Thanks Storm.

Thanks Andrey, okay I see what you mean.

Thanks John and a big thank you to everyone who has written in this post.

 

[JohnQuixote]

Date: 7/14/2007 7:52:55 PM
Author: strmrdr

for a 34.8 crown it again goes off a cliff at 41.6

I’m sure everyone reading at the WFDB will take it under advisement Strm.

Ray-Trace is a nice effort but useless here. It doesn’t account for differences in tonal body color. You would need to incorporate technology like SAS2000 and even then you'd need specific absorption spectrum. Add symmetry variations, table reflection dynamics, bruted vs faceted girdle, consistency… you get the idea.

Even D-Z color grading is done on a linear scale that doesn’t account for tone – and this is done from the side, not face-up.

I know this makes you all a-bristle. “You deny my ray-trace?! Heresy!” (sound of cursing and a clay stein banging on table) but nothing can interpret the collective effects of tonal body color and cut for a particular gemstone except the human eyes.

I assure you that if you’d spent a lifetime cutting diamonds I'd listen to you - even without the software. As it stands I’m glad this thread has evolved (minus personal) because this is a good GENERAL topic.

Date: 7/14/2007 8:07:06 PM
Author: strmrdr
nice anology...
As far as Im concerned I have done all I can to help Pyramid so im out.
If you want to discuss entrapment at a later date then that's kewl.

I'm happy to.

 

[Serg]

Date: 7/13/2007 1:48:41 PM
Author: BrianTheCutter



With respect to the analysts, as a diamond cutter my grandfather and father taught me the only reason to go over 40.9 is to either darken the stone or hold more weight. It is a fact. This is not about labs or beauty it is about dollars and cents.

Blocking the pavilion at 41 instead of 40.75 can eliminate +/- 1% of waste in sawable octahedron. In a 100,000 carat production that’s 1000 cts or more! This is $4,500,000.00 additional profit at an avg wholesale price of $4500/ct. It is no wonder so many manufacturers are on record saying 41 is fine…

I disagree because it is a perilous threshold for color entrapment. Sorry guys, but this is something the labs and theorists do not pay heed to. Go much steeper or shallower than Tolkowsky’s 40.75 and you increase the intensity of color in a stone. It’s unavoidable. I’ve seen it since the days when my grandfather was teaching me. Once you’re over 40.9 in sizes over half a carat this effect kicks into place and the stone darkens further as you increase the angle. Table reflection becomes bigger as pavilion angle increases and can exaggerate the effect. Crowns may be adjusted to maximize entrapment but the pavilion is what is key - which is why fancy-colored stones are cut deep or shallow to intensify their color.

I appreciate John Pollard and others talking about lab grading but it’s simply not useful in this situation. Nothing but live analysis will show color entrapment. Not theses, not photos, not videos, nothing but human eyes. The AGS ray-trace does not pick up color entrapment. GIA includes combos at the steep end of EX that retain weight, entrap color and produce poor looking stones with small spread (no one will deny this). This has allowed manufacturers to push limits at the expense of beauty.

As margins shrink and rough prices climb cutters are pressed to save as much weight as possible. This is the reason you find pavilions creeping up and fewer 40.75 angles. It’s simply not as profitable to produce them in some situations (by the way, 1-5ct goods in collection colors have gone up in price again). 41 combinations are close enough to ‘make the grade’ at labs and they are better money-makers for cutters. My family has always aimed for Tolkowsky’s pavilion. We could make extra money cutting deeper but that’s not what it’s about – it’s about striving for the best of the best.

Do not misunderstand. I’m speaking as a diamond cutter (and some may say a snob). Combinations at 41 can be beautiful and we don’t tell people not to buy them. In fact, we recommend them to clients seeking to be cost-effective, but they must be inspected firsthand because labs are blind to this issue. Well-cut diamonds can be beautiful at the threshold, but as an expert diamond cutter I do not approve of the reason factories are aiming high and pushing limits. I learned these things at the wheel long before the labs ever graded cut.

Sadly, I expect to see more manufacturers cutting steeper & deeper because they are cutting to make money, not for the most optimum performance. Color entrapment and economics are diamond cutting facts.

Brain,
see several images with Histogram of length ray in diamond . ( Scale from dark -zero length, white is near 7 diameters, blue is 10 diameters

First image is fro P40.75 Cr 35.50/
Avarage path is 1.335 Diameter. For other images see name of files. My respect to your grandfather

 

[Serg]

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[Serg]

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[Serg]

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[Serg]

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[Serg]

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[Lorelei]

Pyramid, I just wanted to pop in and say, that I am really excited for you and hope this is THE ONE!!! If so, perhaps a new thread with pics sometime please?

 

[whatmeworry]

Sergey,
Interesting work. I''m trying to understand what they mean. Longer path lengths = more color entrapment? The princess diagram shows why fancy shapes show more color?

 

[Serg]

Date: 7/15/2007 5:07:33 AM
Author: whatmeworry
Sergey,
Interesting work. I''m trying to understand what they mean. Longer path lengths = more color entrapment? The princess diagram shows why fancy shapes show more color?

1) Yes
2) Why princess could has more color( Final color depends from spectrum too)

 

[diagem]

Date: 7/14/2007 8:00:47 PM
Author: JohnQuixote
We all do now. It''s become a bit silly.

Question: Can a car take that corner at 60 mph?
Topic: We wouldn''t advise it, some cars will skid out at that threshold.
Specific: I disagree, that corner is perfectly safe.
Topic: For some it can be, but many cars have skidded out at that mph.
Specific:You''re wrong!My car never skids out! (shows his car not skidding out).
Topic: Ok.

(ps: some cars still skid out) Depending if their tires are 245 or 255... (40.9 or 41)

I don’t know how much more I can stress Brian’s comments are not about a specific diamond.
Is this going to be a topic or diamond-specific thread?