Trying to understand light performance in colored diamonds

[Lexa]

Hi,

I am in the process of evaluating 2 blue synthetic diamonds. I like some feature of each, and if a third stone could "have it all", I would even be happier. However, if I didn't have a choice between the 2, I would probably not know that differences existed. But I do. There have been at least 3 or 4 other posters that have listed their past similar dilemmas on the MMD forum, and who have also gone through the similar steps of pre-purchase and post-purchase evaluations.

I've also figured out a way to define color that makes some sense to me and allows for comparison. First of all - determining "base" color in a round brilliant colored diamond was difficult with areas of color-contrast and sparkle, but shading the diamond from light on all sides, visually "averaging out" its color, and comparing it next to a Benjamin Moore paint sample cards, seemed like the best choice, and it could potentially allow someone else to compare. Otherwise, mid-range colors of diamonds such as Fancy, Intense, and Vivid fall into range between Aquamarines and Sapphires, and do not allow for a direct comparison to another stone. Topazes are in-between for saturation, however in hue are too greenish to directly compare to the grayish blue of the diamonds.

I've also run their measurements through HCA online. I did not have a better alternative to evaluate their light return pre-purchase, as no colored diamond version of HCA is available.

I'm also not trying to ask which one should I choose - as from the previous posts questions and answers, it boils down to make a decision what is most attractive to you (or in this case me). What I'm trying to do, is understand why each appears the way it does. Any educated guesses or explanations are most welcome. I will post their stats, but not photos - I doubt that my amateurish photos would be able to show any differences. The seller did provide me with videos of the diamonds, in sun and in fluorescent lighting, and other than obvious saturation and size differences, I could not differentiate their light performance from those. I would not be able to create better photos or videos, but I can describe what I see.

Anyway,

Candidate # 1
Fancy Blue (my color grade Benjamin Moore SW6505 Atmospheric)
VVS2 5.44x5.41x3.21 0.58ct
Depth: 59.2% Table: 58.0% Crown: 13.3% 32.8° Pavilion: 42.4% 40.3°
Polish: Very Good, Symmetry: Very Good, Girdle: Thin, Culet: None, Fluorescence: None
HCA 1.3, brilliance very good, fire excellent, scintillation excellent, spread excellent

Candidate #2
Fancy Intense Blue (my color grade Benjamin Moore in-between SW6514 Respite and SW 6515 Leisure Blue)
VS2 5.34x5.30x3.19 0.56 ct
Depth: 60.0% Table: 57.0% Crown: 13.9% 33.9° Pavilion: 41.9% 40.0°
Polish: Very Good, Symmetry: Very Good, Girdle: Medium, Culet: None, Fluorescence: None
HCA 1.6, brilliance very good, fire excellent, scintillation excellent, spread excellent

Now, the way I see them.

Against my skin, #2 has more "presence" even though it is smaller by 0.1 mm diameter of the two. The color makes it look larger or more defined. It could look good in a prong solitaire setting (and not need a halo). I would not consider #1 as a candidate for a prong solitaire settings - it would not have enough presence against my skin. I have minimally tanned Caucasian color skin, skin type II, but I do have a little more yellowish hue than an average person, in case that's helpful information.

In their boxes - which are cut outs in black boxes (inner square black, and all outer sides of the box black) and stones are between two sheets of transparent plastic in the middle, the #1 has better light performance - definitely more brilliance and more fire, as I can judge with my eyes - either within arms distance or from a couple of feet away. Scintillation appears comparable, to my eyes.

Placed in a costume jewelry white metal closed tip full bezel setting (full bezel is how I want the stone set, whether open tip or not, is yet to be determined), #1 still has same light performance with more brilliance and fire. As an additional bonus here, its "presence" is improved, by what I've started to refer to as "halo effect" - this is when a lighter shade colored center stone is surrounded by colorless material (whether a halo of small colorless diamonds, or a half bezel or full bezel) - it creates a basis for comparison, showing off the color of the center stone. This effect appears appealing to me in lower and mid saturations, and not at all at higher saturations (think Kate Middleton ering). Anyway, so the planned setting gives back more "presence" to #1. But #2 is still a more saturated color.

The questions are:
1) Is the better light performance for #1 due to its lighter saturation (Fancy vs. Intense)?
2) Or is it due to HCA 1.3 instead of the #2's HCA 1.6?
3) Would a first time diamond buyer even be capable of visually distinguishing HCA 1.3 from 1.6 if other parameters (symmetry, size, and color) were comparable?
4) Does 0.1 mm size difference affect light performance #1 is larger)?
5) Since HCA was not designed for colored diamonds, does it completely NOT predict the light performance in colored?
6) Or does it still predict it but not as well as for colorless?
7) Is its utility correlated to saturation?

I do know that HCA is also a screening rule-out tool, not a rule-in tool, and other things such as DiamCalc and Ideal Scope were mentioned as more of a rule-in tools.

Can DiamCalc or Ideal Scope be used for colored diamonds?
9) Does anyone know of an online computerized tool that can be used for evaluation of colored diamond's cut and light performance?

I've read old posts - back from June 2008, from Diagem, Karl K (aka strmrdr), and Alexei Zarakhani - about optimization of the cut for blue diamonds, based on differences in blue light refractive index vs. averaged-out wavelength white light refractive index.

10) Has anyone done anything with these ideas? I imagine much would be market-driven... Depending on the market share of blue synthetics, and customer preferences about the cut. If it's just a very small percent, then financially it may not make sense to spend time and money on research and development, if it would only be helpful to a small number of customers...

Thank you in advance for your advice and opinions!

 

[periwinklegirl]

Re: Trying to understand light performance in colored diamon

Hi Lexa,
Thanks for your thoughtful post and good luck with your decision.
Eric has a post somewhere in reply to one of my questions about why the more saturated hues don't refract as much. In fact, he explained, they do, it's just that some of the colour isn't as visible because of the body colour of the diamond. There was more to it than that, but that's more or less what I understood. It should be on here somewhere if you want to dig for it. Or you could just ask him!
I know he's posted on why HCA doesn't work on fcds.

I know you didn't ask for opinions, but here is point to bear in mind. You've already noticed that our general advice to get whichever one you like best.
So I'm curious to know why you want a blue diamond? The fabulous rarity of it? The stunning combination of colour and diamond refraction? There must be a reason, given that you're going to all this time and expense.
So here's my opinion: given that you wanted a blue diamond, get the FIB one. At least you'll be able to see that's blue! Fancy blue is just so barely blue that you can't really tell. Look at it compared to the white background in the videos. The fancy blue stone only looks blue when the background also looks blue. At least, IMHO.

As for the bezel, you know the tinfoil trick? It's on the Coloured Stones forum. You wrap a strip of tinfoil around the stone to see what it will look like bezeled.
Finally, I think you'll enjoy a halo. The clear stones really set off the blue.
I like mine so much I'm going to keep it when I upgrade to a three stone.

Good luck and please keep us posted!

 

[EEFranklin]

Re: Trying to understand light performance in colored diamon

All else being equal, a less-saturated blue will return more white light (and as a result, less blue) than a more-saturated blue. As an elimination metric, I would consider HCA results of 1.3 and 1.6 to be essentially equal, and 0.1mm diameter difference insignificant for light performance differences.

"Ideal" cut and light performance are ultimately evaluating ambient (white) light return (e.g. leakage, etc.). As an easy visualization, if you think of light return as a smooth color gradient with white on one end and black on the other end (independent from the diamond's color), when buying a white diamond it makes the most sense to be as far on the white (ideal) end as practical. With fancy colors, that gradient has white on one end and a certain amount of fancy color (blue in this case) at the other end. The more you move toward white, the further you move away from blue. The difficulty is that the saturation level on the fancy side varies with each diamond. It is perfectly possible to have a poor-cut less saturated diamond with more white light return ("performance") than an "ideal-cut" diamond with higher saturation.

HCA, and every other cut tool, system and chart out there, are designed around return of ambient white light in white diamonds. Their results can be relied on for what they are made to measure, but do not take into account saturation in any way, which is a major factor in fancy colors.

To the best of my knowledge, no chart or formula exists and no study has been done that takes saturation into account when evaluating white light return in fancy colored diamonds. We generally recommend focusing first on the specific color grade you like best. Within that grade, by all means, pick the one with the best white light performance, if that is what you want, but don't pick a saturation you like less just because it scores better on systems built to evaluate white diamonds.

Periwinklegirl is probably referring to this post.

Setting a fancy color in a bezel or halo will give the color a little more contrast ("presence") against the white diamonds or metal around it, making it appear a little more blue than if set in a pronged solitaire. This is certainly something to consider if you are tempted more by #1.

FYI, I tried looking up those Benjamin Moore colors on their website, but didn't find them. Did you find those swatches in a store or app?

 

[Lexa]

Re: Trying to understand light performance in colored diamon

hi Periwinklegirl,

the blue synthetic diamond has both qualities that I wanted from the stone: color+spakliness - i had difficulty deciding between a gemstone and a traditional diamond for the Ering, and colored mined diamonds in hues that are appealing to me (blue and on either color spectrum sides of it - green and violet) are cost-prohibitive, other gems are not sparkly enough and not durable enough. i can't help, but be different also. and my dad used to work in a lab that grew sapphires for industrial purposes, so i always found that fascinating.

the Fancy Blue and Fancy Intense both fulfill my needs and wants - of color+sparkliness. but both have each quality to a different extent. Fancy Blue had more sparkle and a little less color, and Fancy Intense had more color and a little less sparkle. however, even the Fancy Intense is capable of producing orange light sparkles and rainbows, just not as frequently as the Fancy Blue.

in the end I'm 99% sure that I am keeping the Intense. one other characteristic that I additionally enjoy about it - is how much the blue color changes when going from light to dark. Fancy Blue does it also, but the amount of change in Intense is amplified. it's like: this is your diamond (Blue), and this is your diamond on crack (Intense).

thanks for tinfoil info - that was actually the first thing we tried. I consider myself to have good manual dexterity, but was not able to do it with the ~0.5ct stone neatly enough to get the idea. maybe it would have worked easier with a larger size. I bought some bezel things from Michaels - no idea what they are meant to be used for, maybe bracelets or necklaces - they got hoops on either side and some on just one side (i didn't need the hoops), only the bezels. both stones looked fine within the simulated bezel settings. no local jewelers had empty bezels for me to play with, so I had to improvise.

thanks for the halo setting suggestion - but somehow I've reserved it in my mind for a pale-ish champagne-colored or brownish diamond, if I ever get to have one down the road. somehow I like the slightly warm or more neutral colors with white halo better than cool colors. somehow I end up with strong visual pattern preferences, without any logical explanation for it... somehow in my mind halo + champagne = match, and blue or bluish-green + bezel = match, and 1ct colorless + prong solitaire = match. i must have seen many styles/ designs and something about those combinations made them stand out the most for me.

for this ring, I am thinking of having 1mm or 1.5mm colorless diamond accents gypsy-set in the band though. I'll post photos once everything is done. it took me probably 2-3 months to this point, and truly the blue synthetic diamond is a very logical conclusion and combination of most of the ideas my BF and I had about what we wanted our Ering stone to be, as well as the progression of what we thought the setting should look like. as someone who has not worn a ring almost ever, and in general does not wear much jewelry, this was a huge learning experience, as far as learning what's available, and what qualities I wanted my ring and stone to have in the end.

it is late, and i need to stop rambling. i would love to see your new 3stone ring! (that was one idea that i had at some point - maybe even the first one, larger blue or violetish center, with lighter smaller stones on the sides, and the metal band in white gold, even lighter still).

 

[Lexa]

Re: Trying to understand light performance in colored diamon

hi Eric,

thanks for the info on light and color! i also think i've figured out what works best for me.

i got a bunch (and I mean about 50-70) color cards from in-store at Benjamin Moore paint store. each has specific hue color and 7 shades from light to dark of that hue. i took everything they had in greenish, pinkish, purplish, violetish, and bluish colors - so about 10-14 of each color-in various hues, and then each has 7 shades. i figured that would get me covered for most possibilities. i did not take the most intense cards (wasn't shopping for rubies or emeralds at that time), nor any browns either. the cards are not meant for people with OCD (like myself) who are gem-shopping. the cards' intended purpose is to help people match wallpaint color to their existing decor. my sister was using them to match some grays - wall color, bedspread, accent pillows, headboard, carpet, etc - trust me, you don't know the pain of matching colors, till you have to match some grays. anyway, at the store, i was just glad the sales people were busy with other customers to see how many of these i was taking. even i may have gotten embarrassed if they said something to me about that, or just looked at me funny.

originally my BF and i were purchasing an unheated Montana green sapphire and looking at some other gemstones, and the website we used, described their gemstone colors in Pantone color cards (they did emphasize to use physical paper cards, not online color blocks - as computer monitors vary). by mistake, i thought Benjamin Moore and Pantone were the same. not sure where Pantone's can be obtained... for the sapphire, we ended up looking up online Pantone's (on my BF's fancy Mac, not my aging Toshiba), and the one we got was right on, as far as its color description.

i've considered asking you when making the diamond videos to include some common object, like a blue M+M or Bic pen color cap, for reference. but then decided against it, as comparison of opaque candy to a transparent refractive gemstone may not have been of much use. are you considering using color card descriptions on your website?

 

[Garry H (Cut Nut)]

Re: Trying to understand light performance in colored diamon

All else being equal, a less-saturated blue will return more white light (and as a result, less blue) than a more-saturated blue. As an elimination metric, I would consider HCA results of 1.3 and 1.6 to be essentially equal, and 0.1mm diameter difference insignificant for light performance differences.

"Ideal" cut and light performance are ultimately evaluating ambient (white) light return (e.g. leakage, etc.). As an easy visualization, if you think of light return as a smooth color gradient with white on one end and black on the other end (independent from the diamond's color), when buying a white diamond it makes the most sense to be as far on the white (ideal) end as practical. With fancy colors, that gradient has white on one end and a certain amount of fancy color (blue in this case) at the other end. The more you move toward white, the further you move away from blue. The difficulty is that the saturation level on the fancy side varies with each diamond. It is perfectly possible to have a poor-cut less saturated diamond with more white light return ("performance") than an "ideal-cut" diamond with higher saturation.

HCA, and every other cut tool, system and chart out there, are designed around return of ambient white light in white diamonds. Their results can be relied on for what they are made to measure, but do not take into account saturation in any way, which is a major factor in fancy colors.

To the best of my knowledge, no chart or formula exists and no study has been done that takes saturation into account when evaluating white light return in fancy colored diamonds. We generally recommend focusing first on the specific color grade you like best. Within that grade, by all means, pick the one with the best white light performance, if that is what you want, but don't pick a saturation you like less just because it scores better on systems built to evaluate white diamonds.

Periwinklegirl is probably referring to this post.

Setting a fancy color in a bezel or halo will give the color a little more contrast ("presence") against the white diamonds or metal around it, making it appear a little more blue than if set in a pronged solitaire. This is certainly something to consider if you are tempted more by #1.

FYI, I tried looking up those Benjamin Moore colors on their website, but didn't find them. Did you find those swatches in a store or app?

Confirming Eric's comments on HCA as its inventor - for colored diamonds the thing is to keep light bouncing around inside the stone as long as possible - average ray paths of 7x diameter get great results. The brightest round brilliant colourless stones average about 2.5x.

ASET is useful though - as much green as possible, as little red and in a perfect world no blue at all. Any amount of evenly dispersed leakage (white) with small spots of green gets a great result. The blue will cause dark zones and thats bad. Big leakage zones can also cause dark zones.

 

[EEFranklin]

Re: Trying to understand light performance in colored diamon

i got a bunch (and I mean about 50-70) color cards from in-store at Benjamin Moore paint store.

I was visualizing you in the paint store holding up diamonds to the swatches to find a match.

my sister was using them to match some grays - wall color, bedspread, accent pillows, headboard, carpet, etc - trust me, you don't know the pain of matching colors, till you have to match some grays.

I attempted to match white paint for a small home repair. After trying dozens of swatches and a couple of the sample cans, I ended up repainting the whole wall.

by mistake, i thought Benjamin Moore and Pantone were the same. not sure where Pantone's can be obtained...

Pantone is an established and well-defined set of colors used mainly in the printing industry. Full swatches start a little over $100, so isn't the most available or cost-effective approach for consumers trying to find a specific color, though is certainly a defined standard that can be used. Their Color Bridge series has PMS (specific ink), CMYK (most printers) and RGB (monitors) all together, so would probably be the most useful set for a consumer to choose. Diamonds will look slightly different colors in different environments though, so color matching is kind of a moving target, and gems are not flat uniform colors either.

i've considered asking you when making the diamond videos to include some common object, like a blue M+M or Bic pen color cap, for reference. but then decided against it, as comparison of opaque candy to a transparent refractive gemstone may not have been of much use. are you considering using color card descriptions on your website?

It would be useful, at least as a starting point, to put together an assortment of common items (M&M, Bic pen cap, etc.) as a benchmark against the diamond colors. In gemstones, there is a big gap between aquamarine and sapphire, so there isn't much there to compare against. We'll have to go shopping and see what universal colors we can find.

 

[periwinklegirl]

Re: Trying to understand light performance in colored diamon

Hi Lexa,
Congratulations on choosing a FIB created diamond! Excellent choice and I'm sure you'll love it! Of course, I may be slightly biased.
I still love to see mine in all the different types of light. Just wait until yours is set, you'll be trying it all over the place! My favorite is daylight, with no sun. It looks powder blue.

I think it's so cool that your dad used to work in sapphire factory!!! Imagine playing with them as a kid! I have several now, including a lovely Ceylon blue asscher I had cut. I don't have a purple one yet though.

I went with a halo because I have such long fingers that I wanted to give my stone some hand presence. It's just less than 3/4 carat. And I like the contrast between the blue and the white.
Your bezel will look fabulous! Are you doing milgrain or plain?
I like the gypsy set stones idea too.

Thanks for the Michaels tip. I did the tin foil thing with my square sapphire, which helped me decide not to bezel it, but it's quite a bit bigger.

And hey, keep the three-stone idea in mind for the future. DNEA conveniently sells matched blues pairs!
I have a thread on mine somewhere, it's going from a simple halo to three stone halo with blue pear sides (and those aren 't easy to come by, believe me!). But while I've assembled all zof the stones, I stopped to get other things set, so it's on hold for the moment.

Thanks Eric and Gary for enlightening the rest of us. Always informative!

Can't wait to see pics!

 

[Lexa]

Re: Trying to understand light performance in colored diamon

ha! i wish my dad brought home sapphires to play with. never saw them. i don't even know if they bothered to cut them nicely. they were supposed to be somehow used with LED lights and optical technologies.

for my ring, i want something very simple, i'm not very girly and don't own any rings, and other jewelry that i have, i typically forget to wear. anyway, so anything on my hand would already be a big adjustment. maybe i'll add other blue things to the ring in the future, to have more of a matched set (for some reason i like having matched sets of jewelry, yet that still doesn't facilitate me wearing them...)

for your three-stone halo, are you planning something like this (except with blue)?:

 

[Lexa]

Re: Trying to understand light performance in colored diamon

yeah, i didn't take the diamonds to the paint store, i took the paint cards home instead. maybe when my to-do list is shorter at some time in the future, the ones that didn't get scribbled on would get taken back.

i had once successfully avoided having to repaint the ceiling by mixing my own color to match. my walls were some sort of beige, and the ceiling was allegedly a 1/4 or 1/2 mixture of that beige plus whatever white color they use for "base" dilution color. i actually had the paint number from the previous owner. and neither 1/4 nor 1/2 dilutions were matching the ceiling spots that i needed to touch up. so i ended up getting a sample of the white base and mixing it little by little with the beige, smearing a little on the ceiling each time. it was a pain, 12-foot ceiling, tall ladder needed, mixing, climbing up and down, looking up, and painting. but not as much of a pain as to repaint the whole 300 square feet of that room.

i'd imagine wall color matching would be more challenging - as people are more likely to inspect it closely, compared to the ceiling... and sometimes even the brushstrokes, or extra layer of paint would be visible, even if color was same.

 

[periwinklegirl]

Re: Trying to understand light performance in colored diamon

ha! i wish my dad brought home sapphires to play with. never saw them. i don't even know if they bothered to cut them nicely. they were supposed to be somehow used with LED lights and optical technologies.

for your three-stone halo, are you planning something like this (except with blue)?:

Yes, that the general idea, but my centre stone is much smaller (under 3/4 carat).
Here are some of my inspiration pics.
The second one is a three stone with irradiated blue diamonds. Mine are much paler blue, well, except for the deep blue one. Here they are!

 

[periwinklegirl]

Re: Trying to understand light performance in colored diamon

the Fancy Blue and Fancy Intense both fulfill my needs and wants - of color+sparkliness. but both have each quality to a different extent. Fancy Blue had more sparkle and a little less color, and Fancy Intense had more color and a little less sparkle. however, even the Fancy Intense is capable of producing orange light sparkles and rainbows, just not as frequently as the Fancy Blue.

in the end I'm 99% sure that I am keeping the Intense. one other characteristic that I additionally enjoy about it - is how much the blue color changes when going from light to dark. Fancy Blue does it also, but the amount of change in Intense is amplified. it's like: this is your diamond (Blue), and this is your diamond on crack (Intense).

for this ring, I am thinking of having 1mm or 1.5mm colorless diamond accents gypsy-set in the band though. I'll post photos once everything is done. it took me probably 2-3 months to this point, and truly the blue synthetic diamond is a very logical conclusion and combination of most of the ideas my BF and I had about what we wanted our Ering stone to be, as well as the progression of what we thought the setting should look like. as someone who has not worn a ring almost ever, and in general does not wear much jewelry, this was a huge learning experience, as far as learning what's available, and what qualities I wanted my ring and stone to have in the end.

it is late, and i need to stop rambling. i would love to see your new 3stone ring! (that was one idea that i had at some point - maybe even the first one, larger blue or violetish center, with lighter smaller stones on the sides, and the metal band in white gold, even lighter still).

I love the whole "this is your ring on crack" thing! Hilarious!!!
Do you have pics of your design idea?