Maximizing diamond brightness should be at the top of your list if you're buying an engagement ring. After all, few things shine bright like a diamond. Although that may be true, the majority of diamonds are not cut to deliver the highest light performance.

Black by Brian Gavin Hanna Setting

Black by Brian Gavin Diamond Brightness.

In fact, most diamonds are simply cut for maximum yield of carat weight. In that case, the diamond brightness and sparkle factor are never taken into consideration. That's because the diamond cutters think that most people aren’t aware that diamond brightness is dictated by cut quality.

And believe me, this is not a new concept, not at all. Because diamond cutters have been studying the effect of diamond proportions upon light performance since the dawn of time. By the way, light return is described as diamond brightness in Diamond Design by Marcel Tolkowsky, Circa 1919.

Consequently, I suspect that his work was based upon somebody else’s work. In that event, let’s round things off and say that diamond cutters have been studying the effect of proportions on diamond brightness since the dawn of time.

Diamond Brightness Formula by Tolkowsky:

So after a bunch of calculations, Marcel Tolkowsky determined that this is the formula maximizing diamond brightness:

Tolkowsky's Formula for Diamond Brightness.

Tolkowsky's Formula for Diamond Brightness.

  • 34.5° Crown angle.
  • 40.75° Pavilion angle.
  • 53% Table diameter.
  • 59.3% Total depth.
  • Knife-edge girdle.

Now, I know you're probably thinking that I’ve given you the Secret Sauce of the McDiamond industry. However, allow me to draw your attention to the part that references a knife-edge girdle.

Suffice to say that is a bit of a design flaw. Or, to be more accurate, it's a technical impossibility. Because you simply can't cut a round brilliant cut diamond without a measurable girdle edge.

Realistic Proportions for Maximizing Diamond Brightness:

Below is the proportions diagram from a Diamond Quality Document (DQD) from the American Gem Society Laboratory (AGSL). In this case, it's for a 1.668 carat, J-color, VS-1 clarity, round brilliant ideal cut diamond from the Brian Gavin Blue collection. As a matter of fact, those are ideal cut diamonds that exhibit blue fluorescence.

Ideal Proportions Diamond Brightness.

Ideal Proportions for Diamond Brightness.

For the purpose of this example, you want to focus on the scalloped section located between the upper and lower sections. That is the girdle edge of the diamond and it is thin to medium, faceted.

Now, do you see how the thicker areas of the girdle edge line up with the facet point junctions? Apparently Marcel Tolkowsky forgot all about this while calculating the ideal proportions for maximizing diamond brightness.

Of course, that's like a dress maker forgetting that a beautiful woman has a waistline. Whoops! What was good, old Marcel thinking?

Accounting for Girdle Thickness:

Since a measurable girdle edge is an integral part of a round brilliant cut diamond, we need to account for girdle thickness. In that case, some adjustments need to be made to Tolkowsky's Diamond Design.

That explains why the Brian Gavin Blue diamond referenced above, has a 34.7° crown angle offset by a 40.9° pavilion angle. Consequently, this combination is well-known for producing exceptional diamond brightness. In other words, it will create a high volume of light return and a virtual balance of brilliance and dispersion.

Black by Brian Gavin Diamond Fire.

Black by Brian Gavin Diamond Brightness.

Although that may be true, it also requires an adjustment of the table diameter and total depth measurements. That's because diamonds are 3-dimensional geometric models. In that case, if you change the measurements in one section, you need to adjust everything else accordingly.

Be that as it may, fifth-generation diamond cutter Brian Gavin has mastered the art of maximizing diamond brightness. As a matter of fact, he holds the only patent for maximizing light performance in the modern round brilliant cut diamond.

In other words, Brian Gavin is the King of Cut. Of course, you don't have to take my word for it. Because the photograph of a Black by Brian Gavin diamond on the left speaks for itself.

How Blue Fluorescence Affects Diamond Brightness:

The proportions diagram above is for a Brian Gavin Blue fluorescent diamond. In that case, it makes sense to talk about how blue fluorescence can improve your perception of diamond brightness. As a matter of fact, I actually had that diamond sitting on my desk when I first wrote this review on August 26, 2013.

How to Use Diamond Tweezers.

Brian Gavin Blue Fluorescent Diamond.

At that time, I was able to take it for a walk and evaluate the diamond brightness under different lighting environments. As a matter of fact, I snapped this picture with my camera phone in 2013.

Under those circumstances, you shouldn't expect too much from it in terms of demonstrating diamond brightness. In other words, the purpose of this photograph is only to show that it's in my possession.

Rest assured that this diamond has a sparkling personality like most Leo's. Of course, you get extra points if you recognize the astrological reference as it applies to this puppy.

J-color Diamond Medium Blue Fluorescence:

The medium blue fluorescence is not visible within this diamond until it is subjected to black light as can be seen from the picture of the blue fluorescence which is provided on the diamond details page.

Now I realize that this is a J-color diamond, but I selected it because I wanted to demonstrate that it is the proportions of a diamond, and not the body color which controls the brightness of a diamond... and this is where people get all sorts of confused with the terminology that we toss around between the sales floor and the backroom of the store where diamonds are graded. So before we go much further, let's agree on a few diamond grading terms:

How to Describe Diamond Brightness:

  • Brilliance is used to describe how bright our human eyes perceive diamond brightness. However it is not only the amount of light return, but also the perception of intensity created by the internal and external reflections of white light, as judged by looking at the diamond in a face-up position.
  • Dispersion, which is also known as “fire”, is the flashes of colored light that is created by the facets of a diamond. Technically these flashes of light are actually white, but our eyes break them up into colors like red, green and blue.
  • Scintillation is the contrast which is created within a diamond by the light and dark patterns created by the facet pattern; it is also the overall sparkle effect which is created when the diamond is in motion.

Diamond Brightness & Brilliance:

"Diamond Brightness" is another way to describe Brilliance. Obviously, your diamond will look brighter if it exhibits a high volume of light return.  At the same time, the balance of brilliance and dispersion will affect your perception of brightness. In that case, diamond brightness is the most prominent factor of light performance.

Brian Gavin Blue Diamond Brighness.

Brian Gavin Blue Diamond Brightness.

In other words, diamond brightness refers to how brilliant a diamond looks. Consequently, that depends on the volume of light return that is reflecting back up through the crown facets.

From that perspective, diamond brightness is the amount of light being reflected up towards the observer. In that case, the amount of diamond brightness has nothing to do with clarity or color.

For example, theBrian Gavin Blue fluorescent diamond on the left looks quite bright. As a matter of fact, it's J-color, but the high volume of light return and sparkle factor make the diamond seem whiter and brighter.

The Effect of Color on Diamond Brightness:

In the first place, it's important to realize that color and clarity have almost nothing to do with diamond brightness. As a matter of fact, the primary components of light performance are:

  • Proportions.
  • Optical Precision.

Refer to the Five Minute Diamond Buying Guide for the range of proportions we recommend. With regard to optical precision, it is simply the consistency of facet shape, size, and alignment. In other words, optical precision reflects the skill of the cutter. Because it demonstrates their ability to polish the facets of the diamond with precision.

Can J-K Color Diamonds Be Bright?

Under those circumstances, the color of the diamond does not determine the degree of diamond brightness. After all, the proportions and degree of optical precision determine the volume of light return and sparkle factor. Whereas the diamond color is only a measure of hue and saturation or the lack thereof.

F-K Color Diamond Comparison

Diamond Brightness of F-K Color Diamonds.

As an example, take a look at the F-K color Brian Gavin Signature diamonds on the left. Notice how the degree of diamond brightness is comparable despite the difference of several color grades.

As a matter of fact, the F-color diamond on the left is in the colorless range. While the K-color diamond on the right is faint yellow. At least as far as their position in the realm of diamond color grading.

Bright, White & Out of Sight!

In the example shown above, I think it's fairly obvious that the K-color diamond faces up white. Which is not to say that it is as bright as the F-color diamond because it's not in the same spectrum.

Black by Brian Gavin Diamonds Reviews.

Black by Brian Gavin Diamond Brightness.

Out of curiosity, did you notice how I wove the words white and bright into that description? In this case, I'm referring to the brightness of color. Basically, in the same way that they do in a commercial for laundry soap.

Because that is also how they tend to refer to diamond brightness at the sales counter in a jewelry store. Hah! No wonder you guys are confused!

Shall we keep things simple? Drop me a note and I'll help you select a stone that is optimized for diamond brightness. In other words, a diamond that is cut to exhibit the highest volume of light return.

While also exhibiting the type of broad-spectrum sparkle that commands attention from across the room! Like that Black by Brian Gavin puppy on the left!

Super Charge Your Diamond Buying Skills:

Follow the Steps in The Nice Ice® Diamond Buying Blueprint™ and Unlock the Secret for Maximizing Sparkle Factor and Light Performance. These are the Tips & Tricks from the back office of Nice Ice Diamonds.