41 degree pavillion angle

[michaelgem]

My latest article in the Journal of Gemmology speaks directly to most of this discussion. 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).

Interestingly, the geometric 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%.

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. Henry Morse in the 1860’s was the first to determine that a 41 pavilion angle was best for this most critical of the round brilliant’s parameters. Prior to 1860 and his work, 45 was believed to be best. (Remarkably, what was believed best back then was actually the worst when table sizes got large enough to make this point obvious).

“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 1977 graduate diamond cutter, Dirk Verbiest.) 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.)”

That is part of why I titled the article "The Accordance in Round Brilliant Diamond Cutting".

So if you want to split hairs, and we all do, I can say with confidence and a large body of evidence, that a 41 pavilion in combination with the appropriate crown angle and the other 5 parameters is superior to Tolkowsky’s theoretical 40.75 and 34.5.

That is why I explained to the USFG that Diamond Design was Tolkowsky''s attempt to validate with a math and
physics arguement why a 41 degree pavilion angle combined with a 34-35 degree crown angle gave the best brilliance and fire to the 58
facet standard round brilliant cut diamond.
Because his math showed 40.75 and 34.5 as best, it has taken over 80
years for diamond grading institutions to realise what American
diamond cutters learned from Henry Morse back in the 1860''s, that 41
degrees is the center of the Ideal cut pavilion angle, sweet spot,
not 40.75.

If you want Ideal Scope performance similar to and as good as Tolkowsky’s 40.75, 34.5, use 41 and 34. An added bonus is a slightly better yield from octohedral rough.

Ideal regards,

Michael Cowing

 

[WorkingHardforSmallRewards]

Date: 7/13/2007 12:50:04 PMsweet 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).

Interestingly, the geometric 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%.

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.

Just a question here. My first is what exactly do you mean by a "sweet spot"between the two instutions grading? and what exactly do you mean by the "geometric center"?

My thoughts being that just because it is the center of the two grading institutions does not at all mean that it is the best or superior in anyway. Consider if I liked pavilon angles of 40-44 degrees, and a friend of mine like pavilion angles of 41-45 degrees. Just because some particular number, say 42.75, is the center, or the sweet spot, in our grading systems does not mean that it is actually the most beautiful combination. or that some other combination might not be equally as beautiful but simply wasn''t geometrically centered amongst our our options for the simple sake that it is not an equal balance of options to the "left and right," in the real world combinations, of that equally as efficient and beautiful combination. (of course the above numbers do not represent real pav. angles but are simply examples) But I am still uncertain exactly what you mean when you use the above questioned vocabulary, so maybe my hesitation is nonsensical and illogical, I''ll just have to wait and see!

 

[Rhino]

I appreciate this input Mike. One thing I am noticing about the 41 degree angle is that it increases your chances of less or minimal head/body obstruction and increases the chances of the pavilion mains lighting up instead of being black and at 41 degrees you''re not getting the leakage in the lower halves contributing to a ring of death increasing the chances of not only the mains lighting up but also the entire pavilion.

Again... this is minutia but if you saw the emails I get about folks stressing about this issue and the HCA ... Good post.

Peace,

 

[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.

 

[michaelgem]

Working asks good questions that a read of my article at http://www.acagemlab.com/articles/sweetspot/index.html should answer.

The round brilliant cut sweet spot

If you play or watch golf or tennis, no doubt
you will have heard about the ''sweet spot''.
This is the area near the middle of a club or
racket where the ball is struck with maximum
control and speed. Striking the ball within the
sweet spot causes it to respond with the best,
most consistent performance.

There is also a ''sweet spot'' in terms of
cutting angles and proportions for peak
diamond performance. The range of this
sweet spot encompasses pavilion and crown
angles long associated with the ''Ideal''
cut. In this sense, the range of angles and
proportions said by GIA and AGS to give
the best brilliance, fire and sparkle, are
their respective sweet spots. When the
cutter fashions the diamond with sufficient
craftsmanship to obtain a diamond within
the sweet spot range, the diamond responds
with the best light performance and beauty.
In tennis the best athletes use a racket
with the largest sweet spot and aim to hit its
centre. In diamond design, the evolution of
the ''Ideal'' round brilliant has led cutters very
close to the centres of the sweet spot of both
grading systems. Today''s cutters aim close
to the centre of the round brilliant''s sweet
spot when they want to ensure the best light
performance and beauty.

Date: 7/13/2007 12:50:04 PMsweet 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).

Interestingly, the geometric 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%.

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.

Just a question here. My first is what exactly do you mean by a ''sweet spot''between the two instutions grading? and what exactly do you mean by the ''geometric center''?

My thoughts being that just because it is the center of the two grading institutions does not at all mean that it is the best or superior in anyway. Consider if I liked pavilon angles of 40-44 degrees, and a friend of mine like pavilion angles of 41-45 degrees. Just because some particular number, say 42.75, is the center, or the sweet spot, in our grading systems does not mean that it is actually the most beautiful combination. or that some other combination might not be equally as beautiful but simply wasn''t geometrically centered amongst our our options for the simple sake that it is not an equal balance of options to the ''left and right,'' in the real world combinations, of that equally as efficient and beautiful combination. (of course the above numbers do not represent real pav. angles but are simply examples) But I am still uncertain exactly what you mean when you use the above questioned vocabulary, so maybe my hesitation is nonsensical and illogical, I''ll just have to wait and see!

Not at all. Your comments and analogy are very logical. My article points out what may or may not be just a coincidence. And that is the close agreement between AGS and GIA of the sweet spot center, and the closeness to that center of both the angles of Morse and Tolkowsky .

The sweet spot concept emphasizes that there is not one but many combinations of the seven parameters, all within a small range, that result in ideal light performance and beauty. Let us underscore that both Morse and Tolkowsky had it right with respect to the important pavilion and crown main angles. Both determined best angle combinations that are near the centers of the range of the Ideal or Excellent sweet spots.

For the purists on this forum, (that is most of us), the performance within the respective sweet spots of GIA Excellent and AGS Ideal 0 is not perfectly flat, and neither is it monotonically increasing to peak at some magic center point or along some axis. We know it to be a somewhat bumpy terrain that does have somewhat of a ridge along what I call the Axis of Excellent and the Axis of Ideal. But that is for us purists and the typical observer in jewelry store lighting will not likely notice these subtle performance differences.

However, for the purists, there are trade offs within each systems sweet spot range. Up to Morses combination of 41 and 35, I and others have demonstrated that the diamond tends to look brighter as the mains reflect from wider angles further away from head obstruction than does Tolkowsky''s 40.75 and 34.5. So the arguement can be made that this Morse combination that is on the steep/deep edge of the AGS Ideal 0 sweet spot is a better performer to the typical observer eyes in typical illumination than is the Tolkowsky 40.75, 34.5.

As Brian points out, further increases in either pavilion angle or crown angle soon lead to middle ring light leakage and reduction in the contrast aspect of brilliance. As Brian notes as well, steeper pavilion angles and shallower crowns will also lead to pupil dilation in the eye of the diamond ( http://www.acagemlab.com/articles/DiamondEye.htm ) When a diamond''s pavilion is ideal cut, its pupil, or innermost ring of reflections will be about a third the size of the table. If this section is larger than one half the table or one quarter the diamond''s diameter, you are not looking at an Ideal cut diamond.
Ideal regards,

Michael

 

[michaelgem]

Date: 7/13/2007 1:22:08 PM
Author: Rhino
I appreciate this input Mike. One thing I am noticing about the 41 degree angle is that it increases your chances of less or minimal head/body obstruction and increases the chances of the pavilion mains lighting up instead of being black and at 41 degrees you're not getting the leakage in the lower halves contributing to a ring of death increasing the chances of not only the mains lighting up but also the entire pavilion.

Again... this is minutia but if you saw the emails I get about folks stressing about this issue and the HCA ... Good post.

Peace,

Thanks, Jonathan,

I avoid the terms ring of death and no go zone as overemphasizing what is a somewhat subtle effect to many observer's in most lighting circumstances when the angles are only slightly steeper and deeper than those of Tolkowsky. Morses 41 and 35 are in that catagory where middle ring light leakage has not yet become an issue.

A question I think is worth pondering is whether slightly steep/deep diamond cuts, which appear brighter due to less problem with head obstruction, but which have some middle ring light leakage, are on balance better performers in typical illumination than stones cut closer to Tolkowsky's theoretical angles.

I want to acknowlege Brian's comments and experience relative to color entrapment. If slightly steep/deep diamonds appear yellower than the same color diamond cut to Tolkowsky proportions, you would be more concerned about slightly steep deep in an I-J color diamond than you would with a D-F color.

Diamond beauty and optical performance has some interesting tradeoffs, and the consumer is encouraged to come to his/her own conclusions in light of all the expert opinion.

As we love to point out, your milage may vary.

Ideal regards,

Michael

 

[BrianTheCutter]

Date: 7/13/2007 4:20:42 PM
Author: michaelgem

I avoid the terms ring of death and no go zone as overemphasizing what is a somewhat subtle effect to many observer's in most lighting circumstances when the angles are only slightly steeper and deeper than those of Tolkowsky. Morses 41 and 35 are in that catagory where middle ring light leakage has not yet become an issue.

A question I think is worth pondering is whether slightly steep/deep diamond cuts, which appear brighter due to less problem with head obstruction, but which have some middle ring light leakage, are on balance better performers in typical illumination than stones cut closer to Tolkowsky's theoretical angles.

I want to acknowlege Brian's comments and experience relative to color entrapment. If slightly steep/deep diamonds appear yellower than the same color diamond cut to Tolkowsky proportions, you would be more concerned about slightly steep deep in an I-J color diamond than you would with a D-F color.

Diamond beauty and optical performance has some interesting tradeoffs, and the consumer is encouraged to come to his/her own conclusions in light of all the expert opinion.

As we love to point out, your milage may vary.

Ideal regards,

Michael

Thank you Michael. The diamond dust in my blood gets irritated when I see economics forcing cutters to dance near a precipice like 41. Subtle or not the ‘no-go’ zones exist for a reason. I’m also averse to so much table reflection. As you may know, diamond cutters used this phenomenon to judge their cutting for many years before scanners ever existed. When we went too steep it got too dark inside, regardless of color.

Our world’s lighting has changed over the last 100 years. This is exaggerated nowhere more than a modern jewelry store. Sadly, blinding lights kill character in antique cuts so they have become less popular in most stores. Rounds with shallow crowns and spread tables are far more commonplace in jewelry displays these days because those configurations look very bright in sales spotlights. This is understandable, but they have little character to my eyes in normal lighting.

My wife will tell you I’m a hopeless romantic and I believe in a romantic visual balance which includes fire through all lighting conditions. Diamond cutters introduced the word ‘fire’…It was used to describe diamond beauty by those who cut under the gas lantern long ago, a literal description of the big colorful dispersion seen in the diamonds and lighting conditions of their era. It is why OMC, OEC and cushion cuts boast short lower girdle halves and high crowns – to bring out the biggest color and life of the stone. Times have changed and fiery cuts are not as common, but in modern rounds I believe in crown and table combinations in the 15-16% range to provide intense fire in and out of modern lighting. This may be a taste departure between us but it has served me and my constituents well. Deeper pavilions leave less room for crown height. At 41 it is still possible and, as I have said, these can be beautiful stones but they simply don’t sit in the center of the bulls-eye for me. Others can do what economics force and the labs permit. This has never bothered me and I’ve never changed from the parameters I’ve always held to. Many diamonds shine and taste varies.

I have heard you say that you answer to a “higher authority” in terms of symmetry. You know my feelings on this and I suspect we will both be grateful when someone begins to take optical symmetry, or asymmetry, into account with regard to performance benefits.

 

[Garry H (Cut Nut)]

Date: 7/13/2007 1:21:13 PM
Author: WorkingHardforSmallRewards

Date: 7/13/2007 12:50:04 PMsweet 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).

Interestingly, the geometric 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%.

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.

Just a question here. My first is what exactly do you mean by a ''sweet spot''between the two instutions grading? and what exactly do you mean by the ''geometric center''?

My thoughts being that just because it is the center of the two grading institutions does not at all mean that it is the best or superior in anyway. Consider if I liked pavilon angles of 40-44 degrees, and a friend of mine like pavilion angles of 41-45 degrees. Just because some particular number, say 42.75, is the center, or the sweet spot, in our grading systems does not mean that it is actually the most beautiful combination. or that some other combination might not be equally as beautiful but simply wasn''t geometrically centered amongst our our options for the simple sake that it is not an equal balance of options to the ''left and right,'' in the real world combinations, of that equally as efficient and beautiful combination. (of course the above numbers do not represent real pav. angles but are simply examples) But I am still uncertain exactly what you mean when you use the above questioned vocabulary, so maybe my hesitation is nonsensical and illogical, I''ll just have to wait and see!

Working Hard that is an excellent question - if you look at a map with iso bars like a weather pressure map, or a topographic map, it is very common that the peak or trough is not in the center of the previous iso bar circle/oval.

The same is apparent on this map from the GIA# (which I used to show how GIA came up with evidence for a relationship beteween crown and pavilion angles even though they disagreed at the time).

Interestingly you can see that this GIA data also supports around 41 / 34, but it equally supports 42 / 31.5 and 40.2 / 36.5. Personally I find that debates over a pavilion angle are really rather naive, because there simply is not one correct sweet pavilion spot. It is a bit like saying this coffee from country X is the sweet spot. Or this shiraz is the best wine in the world, or the best red wine in the world, or the best Shiraz in the world. It is so predictive and superior to suggest that people should have an idea or concept or ideaolgy forced upon them by a bunch of nerds.

It is far better that we give the market and buyers useful information.
For instance the shallow crown diamonds with a good pavilion angle combination appear to have more brightness, and the steep crown angles with the right pavilion angles have a bit more firey appearance. Who is to say that this is the best combination?
Just as who is it that says that the best diamond standard is based on an 8 inch observation distance because soldiers can see rom that distance when more than 1/2 the worlds population with enough money to buy a diamond can not focus from closer than 12 or 14 inches even with their 2x reading glasses.

Can we please have grading systems that allow for a bit of personal choice?


This map was part of the 1998 http://lgdl.gia.edu/pdfs/Fall_1998_Cut.pdf brilliance paper.
#The map has black lines that I drew on it.

 

[strmrdr]

Date: 7/13/2007 8:26:49 PM
Author: Garry H (Cut Nut)

It is far better that we give the market and buyers useful information.
For instance the shallow crown diamonds with a good pavilion angle combination appear to have more brightness, and the steep crown angles with the right pavilion angles have a bit more firey appearance. Who is to say that this is the best combination?

The person buying and viewing the stone.
back on topic...
I will take all the 41/34s and give em a good home if anyone wants to get rid of em for free :}
If I buy another round it will be in the 41/34/80lgf% range with H&A because everyone of them that I have seen I have prefered over other combos I have compared them too.

 

[Garry H (Cut Nut)]

Date: 7/13/2007 11:59:55 PM
Author: strmrdr

Date: 7/13/2007 8:26:49 PM
Author: Garry H (Cut Nut)

It is far better that we give the market and buyers useful information.
For instance the shallow crown diamonds with a good pavilion angle combination appear to have more brightness, and the steep crown angles with the right pavilion angles have a bit more firey appearance. Who is to say that this is the best combination?

The person buying and viewing the stone.
back on topic...
I will take all the 41/34s and give em a good home if anyone wants to get rid of em for free :}
If I buy another round it will be in the 41/34/80lgf% range with H&A because everyone of them that I have seen I have prefered over other combos I have compared them too.

Have you seen well cut BIC''s and FIC''s Storm?
have you done dirty clean diamond comparison tests?

 

[pyramid]

Is a 34/41 considered a shallow/deep, I thought shallow was more like 32 and under?

 

[WinkHPD]

Date: 7/13/2007 11:59:55 PM
Author: strmrdr

Date: 7/13/2007 8:26:49 PM

Author: Garry H (Cut Nut)


It is far better that we give the market and buyers useful information.

For instance the shallow crown diamonds with a good pavilion angle combination appear to have more brightness, and the steep crown angles with the right pavilion angles have a bit more firey appearance. Who is to say that this is the best combination?

The person buying and viewing the stone.

back on topic...

I will take all the 41/34s and give em a good home if anyone wants to get rid of em for free :}

If I buy another round it will be in the 41/34/80lgf% range with H&A because everyone of them that I have seen I have prefered over other combos I have compared them too.

But here in lies the problem. YOU have preferred.

Storm, this is like other issues that we have discussed. Your preferences are YOURS. They do not a market make, nor a valid scientific decision make either.

You have made it abundantly clear that you do not like many things that some of the best minds in the business like, and you have been fairly successful in convincing members of this board not to buy things that YOU do not like.

In this case you are stating that it is best to buy what you DO like, without realizing that most of the 41/34/80lgf stones are NOT going to be as tightly cut as what Rhino has been able to show you. MOST of those stones would be beautiful, but not so beautiful as a stone cut to the standards of a master cutter like Brian or the cutters that Paul employs.

These are men who look at hundreds, even thousands, of stones every month.

I completely respect your right to have opinions and tastes. You know that I have great respect and admiration for you and how hard you have worked to learn so much about our business. You are one of the most influential prosumers on this board. As such I implore you to use your knowledge and position responsibly.

Stating that you have seen some incredible looking 41/34 combinations and knowing them to be especially well cut is one thing, and responsible. Stating that you prefer them above all other combinations, AND FORGETTING TO MENTION THAT MOST SUCH STONES WILL NOT BE SO PRECISELY CUT AND WILL THUS SCORE LOWER ON THE AGS SCALE THAN THE ONES THAT YOU PREFER, is entirely another.

Wink

 

[WorkingHardforSmallRewards]

Time to chime in again. Thanks Gary and MG for taking the time to respond to my questions, I'll have to take some more time to look over them.

Date: 7/14/2007 11:26:19 AM
Author: Wink

But here in lies the problem. YOU have preferred.


Storm, this is like other issues that we have discussed. Your preferences are YOURS. They do not a market make, nor a valid scientific decision make either.


You have made it abundantly clear that you do not like many things that some of the best minds in the business like, and you have been fairly successful in convincing members of this board not to buy things that YOU do not like.


In this case you are stating that it is best to buy what you DO like, without realizing that most of the 41/34/80lgf stones are NOT going to be as tightly cut as what Rhino has been able to show you. MOST of those stones would be beautiful, but not so beautiful as a stone cut to the standards of a master cutter like Brian or the cutters that Paul employs.


These are men who look at hundreds, even thousands, of stones every month.


I completely respect your right to have opinions and tastes. You know that I have great respect and admiration for you and how hard you have worked to learn so much about our business. You are one of the most influential prosumers on this board. As such I implore you to use your knowledge and position responsibly.


Stating that you have seen some incredible looking 41/34 combinations and knowing them to be especially well cut is one thing, and responsible. Stating that you prefer them above all other combinations, AND FORGETTING TO MENTION THAT MOST SUCH STONES WILL NOT BE SO PRECISELY CUT AND WILL THUS SCORE LOWER ON THE AGS SCALE THAN THE ONES THAT YOU PREFER, is entirely another.


Wink

It's always good to see people looking out for us consumers but don't forget that the focus of this entire thread was the scientific analysis of 41 degree pavilion angles in particular coupled with 34+ crown angles. The scientific aspect of it has been covered fairly thoroughly in the previous 101 post (along with some mention of my waist size I believe), though there are still alot of unanswered questions, and so if a consumer were to read strmdr's post and take it out of context of the thread then that would really be his/her own responsibility.

 

[strmrdr]

Date: 7/14/2007 11:26:19 AM
Author: Wink

In this case you are stating that it is best to buy what you DO like, without realizing that most of the 41/34/80lgf stones are NOT going to be as tightly cut as what Rhino has been able to show you. MOST of those stones would be beautiful, but not so beautiful as a stone cut to the standards of a master cutter like Brian or the cutters that Paul employs.

Wink

You out of line Wink, Jon has nothing to do with the stones of that combo I have seen they were at a local b&m.
They were very well cut and since they dont have a helium machine I cant tell you how tight they were but I expect the super tight stones(very important per Paul) that Jon does sell too be even better.
The did however have picture perfect hearts (The most important thing according to Brian).

Paul''s and Brian''s cutting targets are slightly different who is wrong?
neither they just cut too different sweet spots.
41/34 is another sweet spot.

 

[WinkHPD]

Date: 7/13/2007 1:22:08 PM
Author: Rhino
One thing I am noticing about the 41 degree angle is that it increases your chances of less or minimal head/body obstruction and increases the chances of the pavilion mains lighting up instead of being black

Peace,

Instead of being black? When do we ever see black pavilion mains except in photographs and in reflector technology?

Let''s assume for second that you could duplicate this effect in real life, as James Caudill has explained, the instant your heart beat your hand would quiver enough to cause the black to turn bright and the bright to turn dark, and that is what we call scintillation, and scintillation is a good thing! Add now the fact that what you really see are bazillions of tiny flashes of light and dark constantly changing as the stone moves in relation to your eye, and now tell me please how is this a bad thing?

My friend, I think you need to rethink that statement, as it appears to me to be in contrast to the research done by AGS and GIA over the past couple of years.

Wink

P.S. James Caudill is part of the brilliant research team at the American Gem Society Trade Laboratory.

 

[strmrdr]

Date: 7/14/2007 5:43:21 AM
Author: Garry H (Cut Nut)

Have you seen well cut BIC''s and FIC''s Storm?
have you done dirty clean diamond comparison tests?

Iv seen one FIC and liked it, id consider it for a pendant it was pretty but not my preferred personality.
BIC''s, Iv seen some shallow/shallows someone I know has one in her e-ring and its nice at arms length a little bit of an obstruction issue up close, she loves it. Is it a BIC, no clue.

b&m''s wouldn''t like me putting grease on their diamonds.

 

[strmrdr]

Date: 7/14/2007 12:11:51 PM
Author: Wink

Date: 7/13/2007 1:22:08 PM
Author: Rhino
One thing I am noticing about the 41 degree angle is that it increases your chances of less or minimal head/body obstruction and increases the chances of the pavilion mains lighting up instead of being black

Peace,

Instead of being black? When do we ever see black pavilion mains except in photographs and in reflector technology?

I am at this very moment looking at black arrows in the diamond you sold me.
purdy

edit: not using a scope of any kind either.

 

[diagem]

Date: 7/14/2007 11:26:19 AM
Author: Wink

..." but not so beautiful as a stone cut to the standards of a master cutter like Brian or the cutters that Paul employs.

These are men who look at hundreds, even thousands, of stones every month..."


Wink

Since you have mentioned "master cutter"...
Can you elaborate when or what a cutter to do to reach this level to be called a master cutter?

 

[Cehrabehra]

Date: 7/14/2007 12:28:07 PM
Author: strmrdr

Date: 7/14/2007 12:11:51 PM
Author: Wink

Date: 7/13/2007 1:22:08 PM
Author: Rhino
One thing I am noticing about the 41 degree angle is that it increases your chances of less or minimal head/body obstruction and increases the chances of the pavilion mains lighting up instead of being black

Peace,

Instead of being black? When do we ever see black pavilion mains except in photographs and in reflector technology?

I am at this very moment looking at black arrows in the diamond you sold me.
purdy

edit: not using a scope of any kind either.

are you wearing a black shirt? My "bowtie" only shows when I wear black, which I do a lot.

 

[strmrdr]

Date: 7/14/2007 12:42:41 PM
Author: Cehrabehra
are you wearing a black shirt? My ''bowtie'' only shows when I wear black, which I do a lot.

yep black shirt.
close your eyes
*takes off shirt*
still see em.
*puts on blue shirt*
wow when I hold it just right they are now blue/black
light grey shirt is next
can still see em
steps outside: boo I want my arrows back.
.................
The lighting in my apartment is near perfect for seeing arrows, diffused low level fluorescent lighting.

 

[Cehrabehra]

Date: 7/14/2007 11:26:19 AM
Author: Wink

But here in lies the problem. YOU have preferred.

Storm, this is like other issues that we have discussed. Your preferences are YOURS. They do not a market make, nor a valid scientific decision make either.

You have made it abundantly clear that you do not like many things that some of the best minds in the business like, and you have been fairly successful in convincing members of this board not to buy things that YOU do not like.

In this case you are stating that it is best to buy what you DO like, without realizing that most of the 41/34/80lgf stones are NOT going to be as tightly cut as what Rhino has been able to show you. MOST of those stones would be beautiful, but not so beautiful as a stone cut to the standards of a master cutter like Brian or the cutters that Paul employs.

These are men who look at hundreds, even thousands, of stones every month.

I completely respect your right to have opinions and tastes. You know that I have great respect and admiration for you and how hard you have worked to learn so much about our business. You are one of the most influential prosumers on this board. As such I implore you to use your knowledge and position responsibly.

Stating that you have seen some incredible looking 41/34 combinations and knowing them to be especially well cut is one thing, and responsible. Stating that you prefer them above all other combinations, AND FORGETTING TO MENTION THAT MOST SUCH STONES WILL NOT BE SO PRECISELY CUT AND WILL THUS SCORE LOWER ON THE AGS SCALE THAN THE ONES THAT YOU PREFER, is entirely another.

Wink

Even amongst experts there are different preferences - there is more than one pinacle, we (in general) agreed on this before. Personal opinions are not exclusive to the self-taught pricescope consumer. And no matter WHAT the angles are, if the stone isn''t precisely cut there are going to be some problems. Your last paragraph above looks like you are saying that only 41/34 combinations will suffer for being "not so precisely cut".

 

[WorkingHardforSmallRewards]

Date: 7/14/2007 12:55:52 PM
Author: Cehrabehra

Even amongst experts there are different preferences - there is more than one pinacle, we (in general) agreed on this before. Personal opinions are not exclusive to the self-taught pricescope consumer. And no matter WHAT the angles are, if the stone isn't precisely cut there are going to be some problems. Your last paragraph above looks like you are saying that only 41/34 combinations will suffer for being 'not so precisely cut'.

This thread is getting a little intense for me so I will stay out after this, until it calms down. But because Wink is getting alot of questions at once I will go ahead and respond to this one. The 41 degree point has been described throughout this thread as a threshold of sorts. Once you hit that point, it becomes similar to walking a thin line where very small deviations in the wrong direction can send you falling into a "dark abyss" (dramatic isn't it). Thus if a number of the facets are even slightly off, it can supposedly have a noticeable affect on the diamond. Whereas, say 40.8..well, obviously it needs to be well cut, but it seems from this thread that there is some slight margin of error allowed where it will not have as significant an effect as it would when you are "straddling the fence" so to speak in the 41 range. This was emphasized numerous times throughout the thread but there are simply too many post for me to go searching through all of them to quote.

 

[Cehrabehra]

Date: 7/13/2007 4:20:42 PM
Author: michaelgem

I want to acknowlege Brian''s comments and experience relative to color entrapment. If slightly steep/deep diamonds appear yellower than the same color diamond cut to Tolkowsky proportions, you would be more concerned about slightly steep deep in an I-J color diamond than you would with a D-F color.

Diamond beauty and optical performance has some interesting tradeoffs, and the consumer is encouraged to come to his/her own conclusions in light of all the expert opinion.

When I read Brian''s post I was thinking something along these lines but you''ve articulated it very well. If the goal is to only have stones that appear white (which is extremely popular and a reasonable goal) then it would be all the more important to follow Brian''s thought on this, he was very good at explaining the cons of having a stone cut too far from tolk. For me though, and I realize this is just one opinion and albeit the lowly opinion of a mere consumer, but to me the colors of the diamond are beautiful. Now, I also don''t agree with cutting colored diamonds to enhance color (hee - another lowly consumer opinion) because I love refraction and I think that the colors of the diamonds are pretty in their natural state. It is a nice illusion to make a diamond look whiter or yellower than it really is, but there''s also nothing wrong in MY world with having diamonds look exactly the color they are. In fact I think if the diamond world embraced this there would be more demand for all of that K-S rough. Those are the diamonds you can''t really make white and you can''t really make yellow... I think the problem is partly in the minds of those who think only in terms of white and intense yellow. But again, just my lowly opinion. Of course if the whole gamut was opened up it may or may not decrease demand for the extremes (not eliminate, just decrease)

 

[WinkHPD]

Date: 7/14/2007 12:28:07 PM
Author: strmrdr


I am at this very moment looking at black arrows in the diamond you sold me.

purdy


edit: not using a scope of any kind either.

Hmm, I am looking at mele of the same size and quality as I sold you and I do not see black arrows unless I cup my hand about the stone, much like a cutter would do to judge the pavilion depth or table shadow.

I am wondering if it is because as as mele (.15cts if I remember correctly) it is because the obstruction or head shadow would be relatively larger than on a larger stone, or it is because that in a stone this size the virtual facets are too small for our eye to detect so you are seeing larger facets than we might in a larger stone where the visual size of the virtual facets is large enough to become visible.

I am not denying that you are seeing them, just wondering why, when I am looking at the same size and quality in a ring of my wife''s and not seeing them. It could also be the lighting where I am versus where you are.

Gotta agree with you though, that is a kicken little stone!

Wink

 

[WinkHPD]

Date: 7/14/2007 12:55:52 PM
Author: Cehrabehra

Date: 7/14/2007 11:26:19 AM

Author: Wink


But here in lies the problem. YOU have preferred.


Storm, this is like other issues that we have discussed. Your preferences are YOURS. They do not a market make, nor a valid scientific decision make either.


You have made it abundantly clear that you do not like many things that some of the best minds in the business like, and you have been fairly successful in convincing members of this board not to buy things that YOU do not like.


In this case you are stating that it is best to buy what you DO like, without realizing that most of the 41/34/80lgf stones are NOT going to be as tightly cut as what Rhino has been able to show you. MOST of those stones would be beautiful, but not so beautiful as a stone cut to the standards of a master cutter like Brian or the cutters that Paul employs.


These are men who look at hundreds, even thousands, of stones every month.


I completely respect your right to have opinions and tastes. You know that I have great respect and admiration for you and how hard you have worked to learn so much about our business. You are one of the most influential prosumers on this board. As such I implore you to use your knowledge and position responsibly.


Stating that you have seen some incredible looking 41/34 combinations and knowing them to be especially well cut is one thing, and responsible. Stating that you prefer them above all other combinations, AND FORGETTING TO MENTION THAT MOST SUCH STONES WILL NOT BE SO PRECISELY CUT AND WILL THUS SCORE LOWER ON THE AGS SCALE THAN THE ONES THAT YOU PREFER, is entirely another.


Wink

Even amongst experts there are different preferences - there is more than one pinacle, we (in general) agreed on this before. Personal opinions are not exclusive to the self-taught pricescope consumer. And no matter WHAT the angles are, if the stone isn''t precisely cut there are going to be some problems. Your last paragraph above looks like you are saying that only 41/34 combinations will suffer for being ''not so precisely cut''.

Not at all my intention, and a point well taken. The reason that the 41 degree pavilion will suffer is that if the stone has an average of 41 then it may well have some of the pavilion facets at 40.6 and some at 41.4. At 41.4 there will be some detrimental effects that may well in fact be eye visible. 41 is at the edge of the cliff. A tightly cut stone and one with excellent optical symmetry will be much less likely to fall over the cliff. (please excuse my poor metaphor.)

Wink

 

[WinkHPD]

Date: 7/14/2007 1:02:43 PM
Author: WorkingHardforSmallRewards

Date: 7/14/2007 12:55:52 PM

Author: Cehrabehra


Even amongst experts there are different preferences - there is more than one pinacle, we (in general) agreed on this before. Personal opinions are not exclusive to the self-taught pricescope consumer. And no matter WHAT the angles are, if the stone isn''t precisely cut there are going to be some problems. Your last paragraph above looks like you are saying that only 41/34 combinations will suffer for being ''not so precisely cut''.

This thread is getting a little intense for me so I will stay out after this, until it calms down. But because Wink is getting alot of questions at once I will go ahead and respond to this one. The 41 degree point has been described throughout this thread as a threshold of sorts. Once you hit that point, it becomes similar to walking a thin line where very small deviations in the wrong direction can send you falling into a ''dark abyss'' (dramatic isn''t it). Thus if a number of the facets are even slightly off, it can supposedly have a noticeable affect on the diamond. Whereas, say 40.8..well, obviously it needs to be well cut, but it seems from this thread that there is some slight margin of error allowed where it will not have as significant an effect as it would when you are ''straddling the fence'' so to speak in the 41 range. This was emphasized numerous times throughout the thread but there are simply too many post for me to go searching through all of them to quote.

LOL, had I but read further it would not have necessary for me to reply. Well said, and thank you for understanding my intention.

Wink

 

[strmrdr]

Date: 7/14/2007 1:17:51 PM
Author: Wink

Date: 7/14/2007 12:28:07 PM
Author: strmrdr


I am at this very moment looking at black arrows in the diamond you sold me.

purdy


edit: not using a scope of any kind either.

Hmm, I am looking at mele of the same size and quality as I sold you and I do not see black arrows unless I cup my hand about the stone, much like a cutter would do to judge the pavilion depth or table shadow.

I am wondering if it is because as as mele (.15cts if I remember correctly) it is because the obstruction or head shadow would be relatively larger than on a larger stone, or it is because that in a stone this size the virtual facets are too small for our eye to detect so you are seeing larger facets than we might in a larger stone where the visual size of the virtual facets is large enough to become visible.

I am not denying that you are seeing them, just wondering why, when I am looking at the same size and quality in a ring of my wife's and not seeing them. It could also be the lighting where I am versus where you are.

Gotta agree with you though, that is a kicken little stone!

Wink

Its the lighting.....
Whch is far more important than .1 degree in pavilion angle we have been going on and on about for 4 pages now.....

 

[WinkHPD]

Date: 7/14/2007 12:50:19 PM
Author: strmrdr


steps outside: boo I want my arrows back.

.................

The lighting in my apartment is near perfect for seeing arrows, diffused low level fluorescent lighting.

Ah, mystery solved.

 

[Rhino]

Hi Brian,

Thanks for your post. I''d like to address some comments and ask some questions if you don''t mind. The OP (Pyramid) recently purchased from us a diamond that is a 1.90ct H VS1 which she has published in various places on the forum and I have done all I could to help answer her questions and relieve her fears because the diamond she has is not, in any sense of the word ...

a. cut for weight (imagine someone accusing an extremely tightly cut diamond weighting 1.90ct, perfect H&A AGS Ideal as being cut for weight?!?!? ludicrous) and
b. is more yellow than any H on the market because her average pavilion angle is 41.0 instead of 40.9. (Again a ludicrous conclusion to arrive at especially since I have both combinations in my possession and one is most definitely NOT yellower than the other).

There are gemologists reading this post who find some of these comments absurd.

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.

41.0 instead of 40.9 darkens a stone?!?!
41.0 instead of 40.9 holds more weight?!?!? What about the crown angle that''s combined with that paviloin angle? This blanket statement is misleading in the minds of consumers.

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…

So can other infintesimal measurements. Some that have absolutely no bearing on the optical performance and some that do. It is our responsibility as gemologists to see and determine this if it indeed does.

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.

Brian ... in the mind of the consumers reading this the interpretation is a 41 degree pavilion angled diamond will appear yellower than one with a 40.9 pavilion angle which I think you would agree is an absolutely ludicrous assumption to arrive at but this is how many are interpreting it.
I hear and understand what you''re saying, however Pyramid and other consumers who are reading this are being led down a path that will lead them to false conclusions. At the end of this post I''d like to use pyramids diamond as an example and see if this is what you''re referring to because she is certainly weighing heavy on your words with respect to her purchase.

I have here in my inventory a 41.0 degree pavilion angled diamond and also a 40.9 pavilion angled diamond which are both H colors. If what you are saying is true one should be more yellow than the other. I''ve brought both stones into as many lighting environments as I could inside and out of my store to see and detect color differences including lab grading standards for color grading. There is absolutely no difference whatsoever and I would challenge any gemologist or person in this industry worth their weight in salt or even consumers to compare the 2 for themselves to see if there is *any* difference at all in either a critical or practical examination. I''m willing to bet that not only they but neither would you be able to distinguish any difference between the two in color. I''m confident of it.

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.

You are correct. Ther are certain steep/deep GIA Ex''s that show it and nothing but live analysis will show color entrapment. As I look at these two H''s, one with a 40.9 and one with a 41.0 degree pavilion angle, what lighting environment can I bring these 2 diamonds into to see what you are talking about? I know what color entrapment is and I demonstrate this to clients (using an I color with a ring of death alongside a K color cut akin to pyramids diamond in office type diffuse lighting) but what you are saying I can not and do not see. Brian, I am willing to ship you these very 2 diamonds to inspect for yourself. To suggest to the consumers here that a 41.0 instead of a 40.9 will show this, particularly in the case of the type of diamond Pyramid has I and others find very misleading. I hope you will clarify.

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.

see below...

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.

As one who purchases diamonds for his inventory based on optical perrformance, quite frankly numbers take a back seat here in our lab. In fact while we provide every single number imaginable in our analysis/reports, they still take a back seat to live examination. As you and I are familiar with certain elements of interpreting online examination with human observation, Brian, does this AGS graded 1.90ct H VS1 ideal cut diamond appear to be compromised in any way?

There is only a .16 degree variance between min/max pavilion angles.
There is only a .31 degree variance between min/max crown angles.
There is only a .19 degree variance between min/max table %.

Not to mention it scores Excellent in every category based on Octonus'' Symmetry grading (which takes variances of the minors into account). This can all be seen in the Helium Report on this diamond at this link. Here are the images of this stone including its Sarin profile.

Your comments in this thread are scaring consumers out of diamonds akin to this which are nothing short of best of the best (less than 1% of diamonds cut in the world)which can be proven in more than one way.
I am proud to feature such a diamond. Not onlly is it AGS Ideal but also meets all requirements for GIA Ex as well. I''ve examined the color alongside other H''s with 40.7-40.9 angles and see not even one iota of color entrapment and you can''t sit there and tell me this is cut for weight becuase I can think of a thousand factories who would have pushed this over 2.00 for the very reasons you state in your post. At a 61.5% depth coupled with the measurements of this diamond and the ultra tight precision to which its been cut along with its optical examination, I want to know if you think this diamond is compromised. Are consumers being mislead by purchasing a diamond like this because your post certainly makes it seem like anyone considering such a stone is getting a 2nd rate diamond.

With regards,

 

[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."