CBI fire

[LightBright]

So, I bought a CBI diamond with the following dimensions:
Table 57%
Crown Angle 34.5 degrees
Crown Percentage 14.8%
Pavilion Angle 40.8 degrees
Pavilion Percentage 43.1%
Depth 61.5%
Star 51
Lower Girdle Facet 77

It’s beautiful, of course, but I still wonder about FIRE. When I was initially selecting the diamond via video, I asked the reps about how to select a diamond that exhibited more fire. They replied that across the spectrum of CBI diamond cuts (of various percentages), all CBI diamonds exhibit similar fire characteristics. EG, that selecting any CBI stone with -any- proportions will give you equivalent fire. EG, just pick any CBI, you get the same performance.

My question to anyone who has seen an in-person comparison of various CBI diamonds: have you seen a consistency in fire? Or are CBIs with smaller tables and higher crowns more firey than ones with larger tables and smaller crowns as one would expect from those types of angles?

I can say that my CBI diamond exhibits all of the beautiful CBI characteristics people here have talked about (very contrasty facets, darkening in bright light while remaining flashy and shimmery, etc.

 

[sledge]

Pics and videos!!

 

[cflutist]

So, I bought a CBI diamond with the following dimensions:
Table 57%
Crown Angle 34.5 degrees
Crown Percentage 14.8%
Pavilion Angle 40.8 degrees
Pavilion Percentage 43.1%
Depth 61.5%
Star 51
Lower Girdle Facet 77

It’s beautiful, of course, but I still wonder about FIRE. When I was initially selecting the diamond via video, I asked the reps about how to select a diamond that exhibited more fire. They replied that across the spectrum of CBI diamond cuts (of various percentages), all CBI diamonds exhibit similar fire characteristics. EG, that selecting any CBI stone with -any- proportions will give you equivalent fire. EG, just pick any CBI, you get the same performance.

My question to anyone who has seen an in-person comparison of various CBI diamonds: have you seen a consistency in fire? Or are CBIs with smaller tables and higher crowns more firey than ones with larger tables and smaller crowns as one would expect from those types of angles?

I can say that my CBI diamond exhibits all of the beautiful CBI characteristics people here have talked about (very contrasty facets, darkening in bright light while remaining flashy and shimmery, etc.

I own 5 CBI diamonds with very small variations in the 2D numbers but can tell you that they all exhibit enormous amounts of fire in different lighting conditions. There are multiple SMTB threads with photos and videos that you can find by searching my user name.

As to why CBIs exhibit consistent fire/dispersion with minute differences in crown angle and table percentages, I am sure @John Pollard would have a technical and thorough answer for that question.

In the meantime, 2.21 F-SI1 CBI in a darkened theater on a cruise ship



2.79 F-VS1 CBI on stage


2.31 Q-VVS2 CBI on stage



The 2.21 F-SI1 CBI was reset with two other CBIs, .53ct each F-VS1 and F-VS2. Those little guys still exhibit fire.

 

[sledge]

I own 5 CBI diamonds with very small variations in the 2D numbers but can tell you that they all exhibit enormous amounts of fire in different lighting conditions. There are multiple SMTB threads with photos and videos that you can find by searching my user name.

As to why CBIs exhibit consistent fire/dispersion with minute differences in crown angle and table percentages, I am sure @John Pollard would have a technical and thorough answer for that question.

In the meantime, 2.21 F-SI1 CBI in a darkened theater on a cruise ship



2.79 F-VS1 CBI on stage


2.31 Q-VVS2 CBI on stage



The 2.21 F-SI1 CBI was reset with two other CBIs, .53ct each F-VS1 and F-VS2. Those little guys still exhibit fire.

Wow, gorgeous!

Do you mind sharing table, depth, CA and PA of each stone with us?

 

[sledge]

Also @cflutist, do you have any side profile shots of your F stonea in the 3 stone setup?

Asking as I'm having some tint heartache over a BGD H I have mounted for my girl. The pavilion is greatly exposed and your F's look icy white from the top. I'm trying to figure out if F will fix her color sensitivity on a side view, which is where she is picking up the tint.

 

[Golden_bird]

Also @cflutist, do you have any side profile shots of your F stonea in the 3 stone setup?

Asking as I'm having some tint heartache over a BGD H I have mounted for my girl. The pavilion is greatly exposed and your F's look icy white from the top. I'm trying to figure out if F will fix her color sensitivity on a side view, which is where she is picking up the tint.

I will tell you that possible to see the tint in H! I have small ,around 0.25 Brian Gavin H vs clarity stone ,and when I opened the box ,I saw the tint right away! Plus I have one bigger Gia graded H stone and I also see in some lighting the tint ! The thing that helped me is to reset the stones in more closed setting with kind of bar , now I don’t see a tint in small stone ,and my big stone is 99% white! You can find my ring on David Klass instagram ,here is the picture

 

[cflutist]

@sledge

Here are two photos of my F color CBI diamonds taken with my phone in my bedroom with "antique" white walls. The diamonds could be picking up a very slight tint from the off-white walls.





A photo of the loose 2.79 F-VS1 CBI from @John Pollard

 

[Athena10X]

I own 5 CBI diamonds with very small variations in the 2D numbers but can tell you that they all exhibit enormous amounts of fire in different lighting conditions. There are multiple SMTB threads with photos and videos that you can find by searching my user name.

As to why CBIs exhibit consistent fire/dispersion with minute differences in crown angle and table percentages, I am sure @John Pollard would have a technical and thorough answer for that question.

In the meantime, 2.21 F-SI1 CBI in a darkened theater on a cruise ship



2.79 F-VS1 CBI on stage


2.31 Q-VVS2 CBI on stage



The 2.21 F-SI1 CBI was reset with two other CBIs, .53ct each F-VS1 and F-VS2. Those little guys still exhibit fire.

One of the many aspects of my CBI that I love is how bright it is in practically dark lighting environments. Somehow, the diamond seems to capture the last vestiges of light and redirect those rays as if under direct sunlight.

 

[sledge]

@sledge

Here are two photos of my F color CBI diamonds taken with my phone in my bedroom with "antique" white walls. The diamonds could be picking up a very slight tint from the off-white walls.





A photo of the loose 2.79 F-VS1 CBI from @John Pollard

Thank you for sharing!

Wow that setting and the stones are just drop dead gorgeous. Great work! I'm assuming CBI supplied the stone via HPD and Wink also did the setting work?

For me, that F looks awesome. While the tint in the my girl's H is minimal I do see it. My girl sees it too, and we are trying to decide if it's bothersome enough to replace or not.

And thank you for the suggestion @Golden_bird. The setting was a custom DK piece that she loves and I am not about to change that. I think in this case with so much of the sides being exposed it would make more sense to swap stones, or leave as-is and learn to love the tint.

 

[LightBright]

One of the many aspects of my CBI that I love is how bright it is in practically dark lighting environments. Somehow, the diamond seems to capture the last vestiges of light and redirect those rays as if under direct sunlight.

Yes. Mine does too. My CBI picks up any vestiges of light. It’s amazing. But I think I see more fire in CFlutist’s CBIs. Sledge, FYI CFutist has posted dimensions in her previous posts in case you want to see them immediately. I’ll try to capture some images of my stone soon. Not too good at photography but I’ll try.

 

[Golden_bird]

Thank you for sharing!

Wow that setting and the stones are just drop dead gorgeous. Great work! I'm assuming CBI supplied the stone via HPD and Wink also did the setting work?

For me, that F looks awesome. While the tint in the my girl's H is minimal I do see it. My girl sees it too, and we are trying to decide if it's bothersome enough to replace or not.

And thank you for the suggestion @Golden_bird. The setting was a custom DK piece that she loves and I am not about to change that. I think in this case with so much of the sides being exposed it would make more sense to swap stones, or leave as-is and learn to love the tint.

I followed your journey ) I would def keep the stone for now and see ! I can see the tint only in my car and in the kitchen in the rest of conditions,it’s white stone ! In the future ,you guys can just purchase completely deferent stone and size ,I think DK can change maybe the head to accommodate a bigger stone ! And if she is sentimental girl ,like myself ,reset the stone in a necklace ,it’s even closer to the heart

 

[diamondseeker2006]

In superideal cut diamonds, the measurements are all within a narrow range. That is why you were told that there isn't a significant difference in fire in CBI stones by your sales reps. Once you are in the superideal category, the lighting is what makes the fire appear. So there's absolutely no way you can compare your diamond's fire with photos of someone else's diamonds, because they lighting is not the same and photos are not the same as what you see with your eyes anyway. Your diamond has outstanding measurements. I think sometimes we have unrealistic expectations of what fire is really like. Again, it's the lighting that is the other essential factor in seeing fire.

 

[LightBright]

CFlutist thanks for sharing your beautiful photography showing icy white F color CBI diamonds. Firey and exquisite!

 

[LightBright]

In superideal cut diamonds, the measurements are all within a narrow range. That is why you were told that there isn't a significant difference in fire in CBI stones by your sales reps. Once you are in the superideal category, the lighting is what makes the fire appear. So there's absolutely no way you can compare your diamond's fire with photos of someone else's diamonds, because they lighting is not the same and photos are not the same as what you see with your eyes anyway. Your diamond has outstanding measurements. I think sometimes we have unrealistic expectations of what fire is really like. Again, it's the lighting that is the other essential factor in seeing fire.

Thank you for this information Diamondseeker. I do think lighting environment has to do with what I’m seeing or not seeing. Full disclosure my stone is still loose and it hasn’t traveled with me to too many venues besides my house. I’m glad you mentioned that the proportions are excellent. I’m looking forward to setting it so I can admire it all day.

 

[Dancing Fire]

Not mine...

https://www.pricescope.com/communit...-h-vs1-cbi-ring-will-be-here-tomorrow.242502/
https://www.pricescope.com/community/threads/showing-off-my-friends-1-23ct-g-si1-cbi-ring.229378/
https://www.pricescope.com/community/threads/showing-off-my-friends-h-vs1-1-75ct-cbi.241642/

 

[rockysalamander]

@sledge
Oh No! You'd qualify for an upgrade from BGD. You'd be upping the color, so just need to up clarity or carat. Has she looked at a G? Its a big price jump from H to F.

 

[the_mother_thing]

Again, it's the lighting that is the other essential factor in seeing fire.

Do you know/recall, which lighting type is it that produces the most fire? I always forget and/or confuse the types when it comes to this ... halogen, LED, CFLs ...

 

[OoohShiny]

Lots of individual point-source lights are best, IIRC - so spotlights, candles, etc.

 

[LightBright]

Do you know/recall, which lighting type is it that produces the most fire? I always forget and/or confuse the types when it comes to this ... halogen, LED, CFLs ...

I just took a trip to Vancouver BC and that city seemed to still use a lot of halogen lights in my hotel and restuarants. My engagement ring with its tiny pave practically exploded off my hand with firey flashes. Awesome light show. I agree with OooShiny says, spotlighting creates fire. Another type of light that creates “fire” is filtered light, such as that under a leafy tree or under filtered light from shutters.

I have mostly LED lights in my house (thanks California) and that type of light seems less effective than halogens for producing colored light, but it produces lots of bright whiter flashes.

 

[OoohShiny]

Trees or shutters will split a large light source into smaller light sources, so effectively the same process as spotlights, I reckon!

 

[cflutist]

Best light in my house is in the bathroom with recessed LED lighting (another CA resident).

Home Depot and Costco are great too.

 

[cflutist]

Thank you for sharing!

Wow that setting and the stones are just drop dead gorgeous. Great work! I'm assuming CBI supplied the stone via HPD and Wink also did the setting work?

For me, that F looks awesome. While the tint in the my girl's H is minimal I do see it. My girl sees it too, and we are trying to decide if it's bothersome enough to replace or not.

And thank you for the suggestion @Golden_bird. The setting was a custom DK piece that she loves and I am not about to change that. I think in this case with so much of the sides being exposed it would make more sense to swap stones, or leave as-is and learn to love the tint.

@sledge

Yes, all of my CBI diamonds are from @Wink at HPD. All of my rings are custom with HPD's bench who btw use the same casting house that Harry Winston uses. It took me 3 CAD designs for each ring to get it the way I wanted them, which is to see the pavilion and cutlet for easy cleaning. I purposely did not have struts across my 3-stone ring so that the pavilions were visible.

I love the setting you designed as is. Your future intended is so fortunate to have you.

 

[John P]

As to why CBIs exhibit consistent fire/dispersion with minute differences in crown angle and table percentages, I am sure @John Pollard would have a technical and thorough answer for that question.

Hi @cflutist and all. Sorry for the delay. I'm happy to answer and wanted to be thorough, as I’ve seen this question in a few places now.

The short story: Crafted by Infinity’s fire proposition is the same, diamond to diamond.

The long story: We have a specific vision for each performance component. We also have the luxury of producing every diamond ourselves. To that end we're achieving 3D cutting goals where symbiosis between the collective facet groups can transcend some of the old rules of thumb.

This is a popular topic among our jewelers, and I’m going to share some of my training material here.

First…

What is fire?

Many people refer to dispersion and fire interchangeably. But in our lexicon they are not the same.

• Dispersion is caused by diamond material. It’s white light split into fans of rainbow colors and exiting the diamond.
• Fire is physiological. If a portion of a dispersive fan enters your pupil your brain sees a colored flash, or ‘fire.’ But if the whole fan enters your pupil you see a white flash, or possibly nothing…

So dispersion is not fire. Dispersion creates potential to perceive fire. But whether you see fire depends on the lighting, how the diamond was crafted and your own physiology.

To elaborate: If a strong dispersive fan passes over your eye and is wider than your pupil diameter you see a colored flash. If that dispersive fan is smaller than your pupil diameter the light is recombined and you see a white flash. If it's too small or weak you see nothing. In optimal cases, a single wide fan passing across your pupil may cause you to see a full suite of shifting chromatic colors, as on the left.



So again: Dispersion happens in all diamonds. But what you see as colored flashes depends on lighting (are there numerous direct light sources?) the cut of the diamond (are its dispersive fans large enough?) and your physiology (are your pupils constricted enough?).

Diamond fire origins

Beautiful antique diamonds are known for producing large, fluid colored flashes (usually at the expense of brightness). This cutting style evolved in an age when one rough diamond octahedron would be shaped into a single polished diamond. The most economical way of making that crystal attractive was to ‘brute’ the rough into a roundish shape – initially done by rubbing two diamonds cemented on sticks against one another. Once girdled, thick pavilion mains were polished on the bottom and extremely high crowns were fashioned on top. This let dispersive fans grow large as they passed through generous diamond material. Fire was the primary attribute and appeal of those cuts. In fact, the descriptor ‘fire’ comes from cutters in those days, who were maximizing the reflections of fire from the gas lamps under which they worked.

Economics and lighting changes

That all changed around 1900. The rotary saw allowed factories to get two diamonds from one rough crystal. Mechanical girdling evolved and jewelry store lighting shifted from gas lamps to incandescent, halogen and LED. Diamond industry economics and lighting advances saw crowns getting lower and lower & pavilion mains getting thinner and thinner. By 1980 the tables had turned - pun intended. From gas lamps and fire-priority to spotlighting schemes and brightness/fire/scint.


The proliferation of bright halogens and LEDs even stimulated a parade of cuts with additional facets, marketed as having ‘extra sparkle.’ True enough, those cuts sizzled like crazy when blasted with spotlights, but most had such reduced performance qualities in normal lighting that they didn’t survive for long. The Leo diamond is a notable exception.

Does higher crown = better fire?

This rule of thumb has been passed down for over a century, and for good reason; All things equal, with complimentary pavilions, a diamond with a high crown and small table should produce more visible fire than a diamond with low crown and large table. It’s simple physics: More crown means more room in the diamond for dispersive fans to grow. Viola…

So it’s a good old rule. But it comes from a world of 2D proportions.

Crafted by Infinity approach

We don’t rely on crown height for primary fire. Our proposition is fueled by 3D compound mirrors. It’s part of the consistent vision I mentioned; marrying brightness-intensity with fire-efficiency.

To be clear; brightness intensity is easy. Any factory can produce bright diamonds if they choose optimal angles and polish with even nominal consistency. Any production can also increase fire using leaps in 2D crown height.

But marrying top brightness intensity with fire-efficiency involves stepping into another world. It requires planning and 3D focus to keep internal reflections unbroken and of specific size. It also requires extra time, expense of weight and fine-tuning of diamond material. This is not graded by labs or mentioned on reports. But successfully applied, the result is larger internal mirror surfaces, and larger, more intense dispersive fans your pupils will see as colored flashes.


So there’s your answer. Any minute differences in 2D proportions are negligible.

The results come from all facets working together, which permits some variance as long as the greater goal is achieved. In fact - and this shocks many of the jewelers I train - the classically considered ‘fire-facets’ actually take a backseat to some key minor facets in our proposition.



Visible implications

The performance characteristics have been consistently described here so I'll leave that to the community. I would just add that our goals for fire deliberately extend to low-lighting conditions where the observers’ pupils become more dilated. The reason I bring that up is because it's where you'll find the 3D compound mirror proposition notably outpaces 2D crown height in bringing fire.

Summary

Basic brightness continues to be numbers-predictable in round diamonds. It’s why the HCA is so simple but effective.

But as it relates to the question here, especially in such a narrow proportions range, achieving 3D symbiosis between collective facet groups can transcend some of the old rules of thumb.

That was a long read. I hope it's interesting and stimulating.

 

[whitewave]

All I know is I am hooked and HPD CBI has my fix

 

[OoohShiny]

Thank you for the excellent information, @John Pollard!

If I am reading and understanding it correctly, would a (not very short!) summarisation be that CBI focuses on aligning and enlarging internal mirrors, to allow and ensure that a light beam entering the crown as a single shaft of white light will start to disperse immediately (due to refractive index of the material?) and the consequent dispersive fan created within the diamond retains 'coherence' along the same light-path (as in it doesn't get split up and the different colours separated into different paths) until it hits the crown facets on the way back out of the diamond, meaning the dispersive fans have the opportunity to be as wide as they can be, but also that all the colours of the rainbow can be seen off a given facet as the diamond and viewer's eyes move relative to each other?

Which would mean that low-light fire performance is still excellent, because although the viewer's pupils are open very wide (therefore increasing the chance of white light being seen rather than dispersion-incurred fire), the dispersive fans are still even wider than the pupil diameter?

And the crown height is less important than in the past because the light-paths within the diamond enable maximum dispersion, to a point that high 'vintage' crowns are not required?

If that is the case, suddenly the whole '3D faceting' thing is starting to make sense in my head... lol

 

[diamondseeker2006]

My favorite lighting for diamonds is halogen, which is often in large warehouse type stores and Walmart. I've bought some bulbs to replace others in my home when they wear out. I would call it the most beautiful lighting for scintillation. My AVRs have higher crowns than most ideal cuts, and they are pretty compelling in halogen lighting, too, since they were also designed to have great light return. I don't have a camera capable of capturing what I see, unfortunately!

This is a good and easy to understand explanation:

https://www.americangemsociety.org/page/sciencescintillation

 

[Double E]

Hi @cflutist and all. Sorry for the delay. I'm happy to answer and wanted to be thorough, as I’ve seen this question in a few places now.

The short story: Crafted by Infinity’s fire proposition is the same, diamond to diamond.

The long story: We have a specific vision for each performance component. We also have the luxury of producing every diamond ourselves. To that end we're achieving 3D cutting goals where symbiosis between the collective facet groups can transcend some of the old rules of thumb.

This is a popular topic among our jewelers, and I’m going to share some of my training material here.

First…

What is fire?

Many people refer to dispersion and fire interchangeably. But in our lexicon they are not the same.

• Dispersion is caused by diamond material. It’s white light split into fans of rainbow colors and exiting the diamond.
• Fire is physiological. If a portion of a dispersive fan enters your pupil your brain sees a colored flash, or ‘fire.’ But if the whole fan enters your pupil you see a white flash, or possibly nothing…

So dispersion is not fire. Dispersion creates potential to perceive fire. But whether you see fire depends on the lighting, how the diamond was crafted and your own physiology.

To elaborate: If a strong dispersive fan passes over your eye and is wider than your pupil diameter you see a colored flash. If that dispersive fan is smaller than your pupil diameter the light is recombined and you see a white flash. If it's too small or weak you see nothing. In optimal cases, a single wide fan passing across your pupil may cause you to see a full suite of shifting chromatic colors, as on the left.



So again: Dispersion happens in all diamonds. But what you see as colored flashes depends on lighting (are there numerous direct light sources?) the cut of the diamond (are its dispersive fans large enough?) and your physiology (are your pupils constricted enough?).

Diamond fire origins

Beautiful antique diamonds are known for producing large, fluid colored flashes (usually at the expense of brightness). This cutting style evolved in an age when one rough diamond octahedron would be shaped into a single polished diamond. The most economical way of making that crystal attractive was to ‘brute’ the rough into a roundish shape – initially done by rubbing two diamonds cemented on sticks against one another. Once girdled, thick pavilion mains were polished on the bottom and extremely high crowns were fashioned on top. This let dispersive fans grow large as they passed through generous diamond material. Fire was the primary attribute and appeal of those cuts. In fact, the descriptor ‘fire’ comes from cutters in those days, who were maximizing the reflections of fire from the gas lamps under which they worked.

Economics and lighting changes

That all changed around 1900. The rotary saw allowed factories to get two diamonds from one rough crystal. Mechanical girdling evolved and jewelry store lighting shifted from gas lamps to incandescent, halogen and LED. Diamond industry economics and lighting advances saw crowns getting lower and lower & pavilion mains getting thinner and thinner. By 1980 the tables had turned - pun intended. From gas lamps and fire-priority to spotlighting schemes and brightness/fire/scint.


The proliferation of bright halogens and LEDs even stimulated a parade of cuts with additional facets, marketed as having ‘extra sparkle.’ True enough, those cuts sizzled like crazy when blasted with spotlights, but most had such reduced performance qualities in normal lighting that they didn’t survive for long. The Leo diamond is a notable exception.

Does higher crown = better fire?

This rule of thumb has been passed down for over a century, and for good reason; All things equal, with complimentary pavilions, a diamond with a high crown and small table should produce more visible fire than a diamond with low crown and large table. It’s simple physics: More crown means more room in the diamond for dispersive fans to grow. Viola…

So it’s a good old rule. But it comes from a world of 2D proportions.

Crafted by Infinity approach

We don’t rely on crown height for primary fire. Our proposition is fueled by 3D compound mirrors. It’s part of the consistent vision I mentioned; marrying brightness-intensity with fire-efficiency.

To be clear; brightness intensity is easy. Any factory can produce bright diamonds if they choose optimal angles and polish with even nominal consistency. Any production can also increase fire using leaps in 2D crown height.

But marrying top brightness intensity with fire-efficiency involves stepping into another world. It requires planning and 3D focus to keep internal reflections unbroken and of specific size. It also requires extra time, expense of weight and fine-tuning of diamond material. This is not graded by labs or mentioned on reports. But successfully applied, the result is larger internal mirror surfaces, and larger, more intense dispersive fans your pupils will see as colored flashes.


So there’s your answer. Any minute differences in 2D proportions are negligible.

The results come from all facets working together, which permits some variance as long as the greater goal is achieved. In fact - and this shocks many of the jewelers I train - the classically considered ‘fire-facets’ actually take a backseat to some key minor facets in our proposition.



Visible implications

The performance characteristics have been consistently described here so I'll leave that to the community. I would just add that our goals for fire deliberately extend to low-lighting conditions where the observers’ pupils become more dilated. The reason I bring that up is because it's where you'll find the 3D compound mirror proposition notably outpaces 2D crown height in bringing fire.

Summary

Basic brightness continues to be numbers-predictable in round diamonds. It’s why the HCA is so simple but effective.

But as it relates to the question here, especially in such a narrow proportions range, achieving 3D symbiosis between collective facet groups can transcend some of the old rules of thumb.

That was a long read. I hope it's interesting and stimulating.

Thanks so much John! As a normal shopper of diamond without any expert knowledge about it, your explanation on the captioned topic is extremely helpful. For me personally, this has cleared some of my worries while I am purchasing only the 2nd diamond for my wife (the first Ideal one).

Besides, I think your share is equally useful even for more experienced shoppers. Thank you LightBright for creating this thread also

 

[cottoncandy]

Bravo! I learned a lot from this comment. Looking forward to owning a CBI stone with many wide rainbow fans one day

Hi @cflutist and all. Sorry for the delay. I'm happy to answer and wanted to be thorough, as I’ve seen this question in a few places now.

The short story: Crafted by Infinity’s fire proposition is the same, diamond to diamond.

The long story: We have a specific vision for each performance component. We also have the luxury of producing every diamond ourselves. To that end we're achieving 3D cutting goals where symbiosis between the collective facet groups can transcend some of the old rules of thumb.

This is a popular topic among our jewelers, and I’m going to share some of my training material here.

First…

What is fire?

Many people refer to dispersion and fire interchangeably. But in our lexicon they are not the same.

• Dispersion is caused by diamond material. It’s white light split into fans of rainbow colors and exiting the diamond.
• Fire is physiological. If a portion of a dispersive fan enters your pupil your brain sees a colored flash, or ‘fire.’ But if the whole fan enters your pupil you see a white flash, or possibly nothing…

So dispersion is not fire. Dispersion creates potential to perceive fire. But whether you see fire depends on the lighting, how the diamond was crafted and your own physiology.

To elaborate: If a strong dispersive fan passes over your eye and is wider than your pupil diameter you see a colored flash. If that dispersive fan is smaller than your pupil diameter the light is recombined and you see a white flash. If it's too small or weak you see nothing. In optimal cases, a single wide fan passing across your pupil may cause you to see a full suite of shifting chromatic colors, as on the left.



So again: Dispersion happens in all diamonds. But what you see as colored flashes depends on lighting (are there numerous direct light sources?) the cut of the diamond (are its dispersive fans large enough?) and your physiology (are your pupils constricted enough?).

Diamond fire origins

Beautiful antique diamonds are known for producing large, fluid colored flashes (usually at the expense of brightness). This cutting style evolved in an age when one rough diamond octahedron would be shaped into a single polished diamond. The most economical way of making that crystal attractive was to ‘brute’ the rough into a roundish shape – initially done by rubbing two diamonds cemented on sticks against one another. Once girdled, thick pavilion mains were polished on the bottom and extremely high crowns were fashioned on top. This let dispersive fans grow large as they passed through generous diamond material. Fire was the primary attribute and appeal of those cuts. In fact, the descriptor ‘fire’ comes from cutters in those days, who were maximizing the reflections of fire from the gas lamps under which they worked.

Economics and lighting changes

That all changed around 1900. The rotary saw allowed factories to get two diamonds from one rough crystal. Mechanical girdling evolved and jewelry store lighting shifted from gas lamps to incandescent, halogen and LED. Diamond industry economics and lighting advances saw crowns getting lower and lower & pavilion mains getting thinner and thinner. By 1980 the tables had turned - pun intended. From gas lamps and fire-priority to spotlighting schemes and brightness/fire/scint.


The proliferation of bright halogens and LEDs even stimulated a parade of cuts with additional facets, marketed as having ‘extra sparkle.’ True enough, those cuts sizzled like crazy when blasted with spotlights, but most had such reduced performance qualities in normal lighting that they didn’t survive for long. The Leo diamond is a notable exception.

Does higher crown = better fire?

This rule of thumb has been passed down for over a century, and for good reason; All things equal, with complimentary pavilions, a diamond with a high crown and small table should produce more visible fire than a diamond with low crown and large table. It’s simple physics: More crown means more room in the diamond for dispersive fans to grow. Viola…

So it’s a good old rule. But it comes from a world of 2D proportions.

Crafted by Infinity approach

We don’t rely on crown height for primary fire. Our proposition is fueled by 3D compound mirrors. It’s part of the consistent vision I mentioned; marrying brightness-intensity with fire-efficiency.

To be clear; brightness intensity is easy. Any factory can produce bright diamonds if they choose optimal angles and polish with even nominal consistency. Any production can also increase fire using leaps in 2D crown height.

But marrying top brightness intensity with fire-efficiency involves stepping into another world. It requires planning and 3D focus to keep internal reflections unbroken and of specific size. It also requires extra time, expense of weight and fine-tuning of diamond material. This is not graded by labs or mentioned on reports. But successfully applied, the result is larger internal mirror surfaces, and larger, more intense dispersive fans your pupils will see as colored flashes.


So there’s your answer. Any minute differences in 2D proportions are negligible.

The results come from all facets working together, which permits some variance as long as the greater goal is achieved. In fact - and this shocks many of the jewelers I train - the classically considered ‘fire-facets’ actually take a backseat to some key minor facets in our proposition.



Visible implications

The performance characteristics have been consistently described here so I'll leave that to the community. I would just add that our goals for fire deliberately extend to low-lighting conditions where the observers’ pupils become more dilated. The reason I bring that up is because it's where you'll find the 3D compound mirror proposition notably outpaces 2D crown height in bringing fire.

Summary

Basic brightness continues to be numbers-predictable in round diamonds. It’s why the HCA is so simple but effective.

But as it relates to the question here, especially in such a narrow proportions range, achieving 3D symbiosis between collective facet groups can transcend some of the old rules of thumb.

That was a long read. I hope it's interesting and stimulating.

 

[sledge]

You know @John Pollard, the thing I worry about is my pupil may not meet your other controlled factors so well. The girls at the eye doc like to tease me and tell me I have squinty eyes. I tell them it's because I can't take in all their beauty.

For the sake of confirming my pupils are within tolerance of CBI's strict tolerances I think HPD/CBI should send me an D/E colored 0.90ct VS2+ stone to make sure. Dimensions need to be 6.18x6.21. Would help my girl with her "tint" issues of an H stone too. Let me know if you need my address.

Seriously, great response. Thank you for sharing and helping shed light on the matter.