Is it worth it to get a diamond recut?

[mwilliamanderson]

So the combination P41Cr34.5 was more risky 100 years ago. With modern cutting and measurements technologies such angles combination has almost zero risk either for cutters or consumers.

Very interesting Serg, thanks for that information! I’m curious how far you would be comfortable increasing the crown angle with a 41 degree pavillion?

 

[sledge]

@Serg it's funny you mention the 34.5/41 combo. I do get nervous with it because of GIA rounding, etc.

That said, the past few weeks in trying to help others find a stone I stumbled on 2-3 different stones with this particular combo. Granted, they were from a super ideal vendor so you'd expect precision cutting, etc.

And while the videos were designed to show off fire, it was obvious (at least to my eyes) that combo is quite lively when executed properly. It was enough of a difference and a combo that I find risky that I actually noted it mentally as it intrigued me.

I am not as well educated about diamonds as you and a few others here but I am beginning to see and appreciate some of the combos that are sometimes considered borderline, or not within normal parameters. But I also think understanding what makes them risky is something the average consumer struggles with as well so it may not always be obvious when you find the nice outliers.

While I appreciate seeing a stone live and letting your eyes be the final judge, I feel if the vast majority of people are shown 3 stones they can pick the most sparkly one but few have a depth of reference to know where their top choice of the 3 actually falls in the overall scheme of beauty. Add nuances of rounding, different precision levels of cutting, enhanced jewelry lighting, general lack of knowledge about diamond cut, etc and it seems the average consumer struggles to pick a good stone without imperative data to confirm (or deny) what their eyes see.

So what better tools and images exist than an ASET or IS image that will help average consumers?

 

[TODiamonds]

Although almost all consumers out there lack the diamond knowledge (other than rudimentary 4Cs) to discern between an average cut vs superideal, I would say in terms of "letting your eyes be the final judge", most can pick out the sparkliest and largest looking diamonds. The only thing they won't be able to discern is color (which the vast majority of us are horrible at, even with our knowledge) and clarity (unless it's a horrible SI2 or lower).

They may not know what makes it sparkly or give it a good spread, but at least intuitively, when compared side to side with other diamonds, my experience has been most people will pick the highest quality diamond, despite their lack of fundamental or technical knowledge.

 

[Wewechew]

@sledge do you have links to those diamonds? I'd be curious to view them

 

[lb0424]

P40.6 Cr36 is optically similar to P40.85 Cr34.5. If you increase Pavilion angle then you have to reduce Crown angle in 6 times. we name it as "SweetLine".

even diamonds with exactly same proportions could have very different performance

I'm perplex with this statement. I thought performance has everything to do with physics. Shouldn't two diamonds with exactly same proportions (using SARIN reports, not GIA cert rounding) give the same performance? Need some education! Thanks

 

[Serg]

I'm perplex with this statement. I thought performance has everything to do with physics. Shouldn't two diamonds with exactly same proportions (using SARIN reports, not GIA cert rounding) give the same performance? Need some education! Thanks

1) There is a big variation in material properties even for diamonds with same clarity and color .
One diamonds are much more crispy then others because a material is more uniform without RI variations( without stria)
2) There is a big variation in facet polishing ( flatness and roughness) even between diamonds with excellent polishing grade. Labs grade mainly edges junctions instead facet flatness and roughness which are much more important for diamond optics .

You can not see such difference in ASET, IS images, Sarin scans but when you compare such diamonds one by one you could easy see a big difference in performance .

 

[lb0424]

1) There is a big variation in material properties even for diamonds with same clarity and color .
One diamonds are much more crispy then others because a material is more uniform without RI variations( without stria)
2) There is a big variation in facet polishing ( flatness and roughness) even between diamonds with excellent polishing grade. Labs grade mainly edges junctions instead facet flatness and roughness which are much more important for diamond optics .

You can not see such difference in ASET, IS images, Sarin scans but when you compare such diamonds one by one you could easy see a big difference in performance .

Thank you for the explanation, Serg. There is a lot of emphasis on "cut" when reading PS posts and not much about "polishing". Where can I read more about polishing to understand more on diamond optics? Thanks again!

 

[Demon]

P40.6 Cr36 is optically similar to P40.85 Cr34.5. If you increase Pavilion angle then you have to reduce Crown angle in 6 times. we name it as "SweetLine".


For my Knowledge, Experience and Taste a diamond with P41( and even 41.2) Cr34.5 has more "Life" than a diamond with "classical Tolkowsky" angles like P40.75Cr34.5.
A combination P40.6Cr36 at least not worse than P40.75Cr34.5.

Do not do your final decision by tools as ASET, IS, H&A. Its are not performance grading tools, they are cyclops rejection tools. You need use side by side comparison to select a best diamond for you .

There are many reasons why a diamond with "Bad IS, ASET" could be better that a diamond with perfect IS, ASET images even if they have same size, same cut, same color and same clarity and same polishing grades.
even diamonds with exactly same proportions could have very different performance

I'm so glad to have read this! A diamond I have has a 41% pavilion and a 34.5 crown. It seems very lively to me, even though I've never compared it with a super ideal, and don't have an ASET.

 

[Serg]

Thank you for the explanation, Serg. There is a lot of emphasis on "cut" when reading PS posts and not much about "polishing". Where can I read more about polishing to understand more on diamond optics? Thanks again!

you could start from wiki

https://en.wikipedia.org/wiki/Mirror

Surface quality[edit]
Surface quality, or surface accuracy, measures the deviations from a perfect, ideal surface shape. Increasing the surface quality reduces distortion, artifacts, and aberration in images, and helps increase coherence, collimation, and reduce unwanted divergence in beams. For plane mirrors, this is often described in terms of flatness, while other surface shapes are compared to an ideal shape. The surface quality is typically measured with items like interferometers or optical flats, and are usually measured in wavelengths of light (λ). These deviations can be much larger or much smaller than the surface roughness. A normal household-mirror made with float glass may have flatness tolerances as low as 9–14λ per inch (25.4 mm), equating to a deviation of 5600 through 8800 nanometers from perfect flatness. Precision ground and polished mirrors intended for lasers or telescopes may have tolerances as high as λ/50 (1/50 of the wavelength of the light, or around 12 nm) across the entire surface.[48][47] The surface quality can be affected by factors such as temperature changes, internal stress in the substrate, or even bending effects that occur when combining materials with different coefficients of thermal expansion, similar to a bimetallic strip.[49]

Surface roughness[edit]
Surface roughness describes the texture of the surface, often in terms of the depth of the microscopic scratches left by the polishing operations. Surface roughness determines how much of the reflection is specular and how much diffuses, controlling how sharp or blurry the image will be.

For perfectly specular reflection, the surface roughness must be kept smaller than the wavelength of the light. Microwaves, which sometimes have a wavelength greater than an inch (~25 mm) can reflect specularly off a metal screen-door, continental ice-sheets, or desert sand, while visible light, having wavelengths of only a few hundred nanometers (a few hundred-thousandths of an inch), must meet a very smooth surface to produce specular reflection. For wavelengths that are approaching or are even shorter than the diameter of the atoms, such as X-rays, specular reflection can only be produced by surfaces that are at a grazing incidence from the rays.

https://en.wikipedia.org/wiki/File:Mirror_distortion_and_artifacts_due_to_flatness_errors.png

"A household mirror, demonstrating distortion and artifacts in the image due to a low degree of flatness. The errors become more apparent when viewed at a steep angle or at long distances."

In a diamond we have multiply "mirrored " reflections and often with steep angles.
MTF( Modular transfer function what describe contrast depends resolution ) for system with 2 reflection is MTFxMTF. So quality of light source image become worse and worse after each reflection .

it is 2d or 3d important reason why fancy cuts with crushed ice type pattern design has less contrast, brightness compare with RBC.
I believe that most diamonds facets have MTF worse than household mirrors (I did not measured MTF for Diamond facets yet because it is not easy task) .

 

[headlight]

you could start from wiki

https://en.wikipedia.org/wiki/Mirror

Surface quality[edit]
Surface quality, or surface accuracy, measures the deviations from a perfect, ideal surface shape. Increasing the surface quality reduces distortion, artifacts, and aberration in images, and helps increase coherence, collimation, and reduce unwanted divergence in beams. For plane mirrors, this is often described in terms of flatness, while other surface shapes are compared to an ideal shape. The surface quality is typically measured with items like interferometers or optical flats, and are usually measured in wavelengths of light (λ). These deviations can be much larger or much smaller than the surface roughness. A normal household-mirror made with float glass may have flatness tolerances as low as 9–14λ per inch (25.4 mm), equating to a deviation of 5600 through 8800 nanometers from perfect flatness. Precision ground and polished mirrors intended for lasers or telescopes may have tolerances as high as λ/50 (1/50 of the wavelength of the light, or around 12 nm) across the entire surface.[48][47] The surface quality can be affected by factors such as temperature changes, internal stress in the substrate, or even bending effects that occur when combining materials with different coefficients of thermal expansion, similar to a bimetallic strip.[49]

Surface roughness[edit]
Surface roughness describes the texture of the surface, often in terms of the depth of the microscopic scratches left by the polishing operations. Surface roughness determines how much of the reflection is specular and how much diffuses, controlling how sharp or blurry the image will be.

For perfectly specular reflection, the surface roughness must be kept smaller than the wavelength of the light. Microwaves, which sometimes have a wavelength greater than an inch (~25 mm) can reflect specularly off a metal screen-door, continental ice-sheets, or desert sand, while visible light, having wavelengths of only a few hundred nanometers (a few hundred-thousandths of an inch), must meet a very smooth surface to produce specular reflection. For wavelengths that are approaching or are even shorter than the diameter of the atoms, such as X-rays, specular reflection can only be produced by surfaces that are at a grazing incidence from the rays.

https://en.wikipedia.org/wiki/File:Mirror_distortion_and_artifacts_due_to_flatness_errors.png

"A household mirror, demonstrating distortion and artifacts in the image due to a low degree of flatness. The errors become more apparent when viewed at a steep angle or at long distances."

In a diamond we have multiply "mirrored " reflections and often with steep angles.
MTF( Modular transfer function what describe contrast depends resolution ) for system with 2 reflection is MTFxMTF. So quality of light source image become worse and worse after each reflection .

it is 2d or 3d important reason why fancy cuts with crushed ice type pattern design has less contrast, brightness compare with RBC.
I believe that most diamonds facets have MTF worse than household mirrors (I did not measured MTF for Diamond facets yet because it is not easy task) .

@Serg, do you think GIA does an adequate job with their polish and symmetry grading (in context to their questionable, at best, cut grading)? I understand if you prefer not to comment in this regard.

 

[Serg]

@Serg, do you think GIA does an adequate job with their polish and symmetry grading (in context to their questionable, at best, cut grading)? I understand if you prefer not to comment in this regard.

There is not any lab that grade diamond facet flatness and roughness .
if we speak about polishing grade they grade just junctions and surface defects as scratches which have minor influence to diamond optics in compare with facet flatness and roughness.
They grade that they see instead that has strong influence to optical performance .

Current Lab grading system ( for polishing and symmetry) pushes cutters to reduce quality of facet flatness.
easiest way to achieve Excellent junctions is to reduce facet flatness ( to use concave facets instead flat facet)

 

[sledge]

There is not any lab that grade diamond facet flatness and roughness .
if we speak about polishing grade they grade just junctions and surface defects as scratches which have minor influence to diamond optics in compare with facet flatness and roughness.
They grade that they see instead that has strong influence to optical performance .

Current Lab grading system ( for polishing and symmetry) pushes cutters to reduce quality of facet flatness.
easiest way to achieve Excellent junctions is to reduce facet flatness ( to use concave facets instead flat facet)

As online purchases continue to soar, how can the industry adapt to educate consumers about facet flatness and roughness and provide some sort of a report that does grade this attribute?

 

[AV_]

ASET, IS, H&A. Its are not performance grading tools, they are cyclops rejection tools.

Screens are flat too.

Video is to read rather than see much like those reflector tools, there might be room for technical wisdom in the same vein.

 

[OoohShiny]

easiest way to achieve Excellent junctions is to reduce facet flatness ( to use concave facets instead flat facet)

How is it possible to create concave facets in a diamond if one is using a flat polishing wheel??! (where concave = a depression in the surface, and convex = a protrusion from the surface)


Thank you for posting that excellent table of the different cut options and their effects on light return/contrast patterns

If red is light return and white is contrast, does that mean the very bottom right corner (super-steep, super-deep) actually returns a lot of light but has no contrast??

 

[TODiamonds]

P40.6 Cr36 is optically similar to P40.85 Cr34.5. If you increase Pavilion angle then you have to reduce Crown angle in 6 times. we name it as "SweetLine".


For my Knowledge, Experience and Taste a diamond with P41( and even 41.2) Cr34.5 has more "Life" than a diamond with "classical Tolkowsky" angles like P40.75Cr34.5.
A combination P40.6Cr36 at least not worse than P40.75Cr34.5.

Do not do your final decision by tools as ASET, IS, H&A. Its are not performance grading tools, they are cyclops rejection tools. You need use side by side comparison to select a best diamond for you .

There are many reasons why a diamond with "Bad IS, ASET" could be better that a diamond with perfect IS, ASET images even if they have same size, same cut, same color and same clarity and same polishing grades.
even diamonds with exactly same proportions could have very different performance

Serg thanks for sharing this table - it is freaking awesome! I've never seen anything like it - really helps visualize the differences between angle combinations. I'm a big fan of the unique insights and thoughtfulness you put into each post.

 

[Serg]

How is it possible to create concave facets in a diamond if one is using a flat polishing wheel??! (where concave = a depression in the surface, and convex = a protrusion from the surface)


Thank you for posting that excellent table of the different cut options and their effects on light return/contrast patterns

If red is light return and white is contrast, does that mean the very bottom right corner (super-steep, super-deep) actually returns a lot of light but has no contrast??

@OoohShiny
You are absolutely right I mixed the words.
Correct statement is:

"The easiest way to achieve Excellent junctions is to reduce facet flatness ( to use convex facets instead flat facets)"

 

[Serg]

If red is light return and white is contrast, does that mean the very bottom right corner (super-steep, super-deep) actually returns a lot of light but has no contrast??

The H&A light had been used to create this table. The H&A light is good to control a diamond optic but it is not good to evaluate a diamond brightness . It does not show a leakage .
There are some bright diamonds in right top corner .

Around 10 years ago we cut MSS17 RBC sample with Crown 39 Pavilion 40 degrees .

https://cutwise.com/diamond/385

What are GIA, AGS grades for this diamond?

 

[Karl_K]

Around 10 years ago we cut MSS17 RBC sample with Crown 39 Pavilion 40 degrees .

https://cutwise.com/diamond/385

What are GIA, AGS grades for this diamond?

For a ring they would not be that wrong due to obstruction past 1/2 arm length.
I have been playing with virtual 40c/40p designs both mrb and oec and they are very interesting.
Put them in a pendant or tiara and they would hold their own with any diamonds.
I can see why they were at one time considered the best OEC style cuts.(primitive measuring tools is another reason they were cut).

 

[TODiamonds]

The H&A light had been used to create this table. The H&A light is good to control a diamond optic but it is not good to evaluate a diamond brightness . It does not show a leakage .

Serg do you have (or can you create) a table like the one above, but for projected ASET images instead of H&A light?

 

[Serg]

Serg do you have (or can you create) a table like the one above, but for projected ASET images instead of H&A light?

I have tables only with IS and H&A lights. Do you need ASET black or ASET white?

 

[TODiamonds]

I have tables only with IS and H&A lights. Do you need ASET black or ASET white?

I'm not sure... whichever one better highlights the light leakage I suppose.

 

[sledge]

I'm not sure... whichever one better highlights the light leakage I suppose.

Thank you @Serg for providing all this data. It is greatly appreciated.

IMO, white shows leakage more easily but a black version would be nice too.

 

[Serg]

@TODiamonds

 

[TODiamonds]

Thanks so much for pulling this together Serg! I've saved this for future reference - really appreciate the time you took to pull this together.

I've never been good at interpreting ASET scans. My rudimentary understanding is: Red = Good, Green = Medicore, White/Gray = Light Leakage (BAD). Black/Blue = contrast. Is that basically the gist of it for those of us who aren't trade professionals?

As an example, I've highlighted 3 different ASET patterns from your table below. Can you give us a quick crash course in how you interpret the scans for A, B, C from your perspective. This would really help educate me on how to view these. Thanks man!

 

[Serg]

Thanks so much for pulling this together
I've never been good at interpreting ASET scans. My rudimentary understanding is: Red = Good, Green = Medicore, White/Gray = Light Leakage (BAD). Black/Blue = contrast. Is that basically the gist of it for those of us who aren't trade professionals?

Above statements are very similar to " The Earth is flat ".

How to explain what "the Earth is sphere" for persons who prefers to see the flat earth"?


There are not bad or good colors in static cyclopes ASET.
Red could be Bad, white could be good.





ASET is not a performance grading tool. ASET is a manufacture repeatability ( consistency) checking tool.
Some ASET modifications could be very helpful as Research tool for professional cut designers.
I am very often use ASET modification that includes body obscuration . Classical ASET is not very helpful for cut designing .
But the flat earth is more practical and simple concept .

 

[Serg]

White/Gray = Light Leakage (BAD). Black/Blue = contrast.

For cyclops observer strong Light leakage looks as Black facet.
Head Obscuration ( Black and Blue) is also Black facet for Cyclops.
Why does Blue mean contrast when White is bad? where is any logic here?
If Blue is contrast then White is also contrast. if White is bad then blue is bad.
but each ASET color could be good and bad depends from a difference that left and right eyes see in this diamond facet.
If both eyes see blue then this facet dead. If both eyes see strong! white then this facet dead.
But if one eye sees white or blue when second eye sees red then this facet creates strong Brilliancy or Fire.
if one eye sees red and second eyes sees green then such facet has more Life in comparison when both eyes see red.

 

[TODiamonds]

So basically what you are saying is that ASET shouldn't be used to judge diamond performance?

 

[Serg]

So basically what you are saying is that ASET shouldn't be used to judge diamond performance?

A diamond with better performance could have "worse" ASET image .
A fancy cut diamond with nice ASET image could have poor performance .

But diamonds with same cut design and with similar ASET images usually have similar performance . It is the reason why ASET is so popular( effective) for selection round diamonds .

 

[distracts]

A diamond with better performance could have "worse" ASET image .
A fancy cut diamond with nice ASET image could have poor performance .

But diamonds with same cut design and with similar ASET images usually have similar performance . It is the reason why ASET is so popular( effective) for selection round diamonds .

I have noticed that in particular emerald cuts with “good” asets do not appeal to me because the facets don’t sparkle the same way the ones with “bad” asets do - they go on and off all at once rather than alternating, basically. Which is exactly what a mostly-red aset would predict, I guess. I think you could probably find a way to read one to find the emerald cuts I like but I haven’t seen enough to know.

 

[TODiamonds]

A diamond with better performance could have "worse" ASET image .
A fancy cut diamond with nice ASET image could have poor performance .

But diamonds with same cut design and with similar ASET images usually have similar performance . It is the reason why ASET is so popular( effective) for selection round diamonds .

Thx. I probably should have clarified I was only referring to round diamonds.