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Measuring Sparkle

AGS’s cut grade system advances to fancy and proprietary cuts.

By Ettagale Blauer
The more symmetrically perfect the diamond cut, the more dazzling the display of light and sparkle. “Essentially what happens within a diamond comes from the relation between the light source, the observer and movement,” says Peter Yantzer, executive director of the American Gem Society (AGS) Laboratories. “You see areas of the diamonds that are illuminated or that go dark.” Thousands of “virtual” facets can be seen because the diamond acts as a compound mirror.
   Light enters and exits the diamond through the crown, breaking up into tiny pieces. The size and placement of the facets dictates not only the number of sparkles available to the viewer but also the size of those sparkles. AGS has turned this seemingly random, but dazzling, display into a measurable element. With its performance-based cut grade system, introduced in 2005, AGS can demonstrate exactly how altering the arrangement of the facets changes the way light acts within the diamond, which, in turn, changes the visual appeal of the diamond to the viewer. That system initially focused on round diamonds, which comprise the vast majority of stones sold in the industry.
   Having conquered this basic shape, AGS moved on to fancy shapes. These are more challenging because they don’t follow the traditional 58-facet pattern of rounds. Newer performance grading systems encompass the oval, emerald and square emerald cuts. Now, AGS has taken the cut grade system into a highly specialized area of diamond shapes: proprietary cuts.


Cutting for Maximum Sparkle
   AGS’s proprietary cut grade system can help a cutter decide not only how to get the most weight from the rough but how to achieve the most sparkling cut. Jason Quick, Yantzer’s lab partner, a Massachusetts Institute of Technology (MIT)–trained mathematician, brings that math background to the process and enthusiastically describes the work on proprietary cuts as “a really cool thing.” Quick, known as “Q” around the lab, explains “our ability to consider a new arrangement of facets using a 3-D model can save a diamond cutter considerable money. We help him choose the most profitable cut and reduce the hours he would spend evaluating cut alternatives.”
   Manufacturers applying for a patent based on a specific arrangement of facets want to know if that arrangement will produce a more beautiful diamond. They want to know how well it will perform. Even the smallest change in the pattern of facets can spell the difference between a highly desirable new cut and one that is just different, but not beautiful. Getting to that point in the design process can be both tedious and expensive when the trial-and-error process is worked out in real diamonds.
   Using the patented technology from its performance-based cut grade system, AGS can do enormous amounts of modeling within its computer systems to determine which arrangement is the one most likely to result in a new, and beautiful, facet design. The computer modeling system predicts how bright a diamond will appear through a system of ray tracing. By analyzing how the light will bounce around in the diamond, it can determine, in advance, the light return of a particular pattern of facets.
   Quick says that, based on the facet arrangement proposed by the manufacturer, “We can create a 3-D model; we can simulate hundreds of thousands of simulations, with different angles. We can pull out the angles and then pull them back in,” seeking the ideal combination and arrangement of facets. The lab also can work with different types of input from the cutter. “We have begun the process without ever seeing a real stone; we can begin with the drawing. Sometimes there are prototypes” to work from.

Computer Confirmation
   Initially, the manufacturer may have an idea of where the best light performance will be but the lab can verify that through computerized 3-D trial and error. To date, AGS has helped manufacturers bring some 40 proprietary cuts to the marketplace. The lab has worked with Asscher, with Hearts on Fire and with the Leo cut, among other well-known brands in the industry.
   When a cutter sends in an actual stone, the AGS lab will analyze it with its computerized system and make recommendations about adjusting the arrangement of facets. This results in a diamond with what Quick describes as “a personality difference” that makes one diamond cut stand out from others, an important distinction in marketing. Manufacturers don’t have the laboratory tools, the computers that AGS has invested in, to do this kind of analysis on their own. For the manufacturers, it’s a win-win situation.
   AGS performs this kind of analysis on a pro bono basis. Ruth Batson, chief executive officer (CEO) of AGS, says, “By offering this technology to manufacturers, we elevate the cutting in our industry. Our mission is to serve the industry.” Of the AGS lab team, Yantzer says, “We are just two guys. By developing performance standards for proprietary cuts, we are building a body of work. Diamonds are cut to a greater level of precision. Diamonds are prettier. While there are differences in taste, our metrics prove that over time, most people who look at these diamonds will say ‘it is beautiful.’ We always have to consider taste. Regarding sparkles, some want many, smaller sparkles; some want a few, larger sparkles. We can measure it, but we don’t dictate.” AGS provides the charts for manufacturers to follow. Ultimately, it’s up to the cutter to decide the direction to take.

Consensus on Beauty
   As Yantzer says, “There are cultural and geographical preferences around the world,” but there is agreement on what makes a diamond beautiful. “It has to be bright, it has to return a lot of light.” For a cutter to succeed, “you need brightness, contrast and dispersion; leakage is the negative.”
   Before deciding on any of the parameters of cut, the lab starts by establishing a standard viewing distance between the viewer and the diamond. Individuals’ ability to view diamonds changes with age. Those at younger ages can look at things closer, Yantzer says. AGS has adopted the military standard for close observation, which is set at a distance of 9.84 inches between viewer and object. AGS takes both that standard and the eyesight of the average human being into consideration when it looks at light return. “We built the effects of human beings into our metrics,” Yantzer adds.
   Working with the elusive element of light return, AGS has succeeded in bringing science to the forefront of diamond design, and in the process, helping cutters and ultimately retailers offer customers the most dazzling diamonds possible — and in the most varied and unique cuts possible.

Article from the Rapaport Magazine - December 2013. To subscribe click here.

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