Benefits of Concave Faceting

How does concave faceting create so much more brilliance than regular flat faceting? Imagine a typical flat, square mirror, Now push the top and bottom closer together so that the reflective side curves toward you. Than take the left and right edges and curve them away from you so that the whole thing is slightly cylindrical.

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By Suzanne WadeMore from this author

When Douglas Hoffman founded PolyMetric Instruments Inc. in Clayton, Washington, and produced the first commercial concave faceting machine in 1990, he threw the gem cutting trade a curve.

Concave faceting involves cutting pavilion facets to curve inward, usually in conjunction with some flat facets on the crown. The curved facets scatter more light into the interior of the stone than traditional flat facets, resulting in a more brilliant gem. The difference is noticeable even to the untrained eye, say gem cutters.

"The optics of the finished gems are remarkable far and away superior to traditional faceting," says Richard Homer, who has won 15 American Gem Trade Association Cutting Edge Awards with his concavefaceted designs. "One of the advantages of concave cutting is that it distributes light much more evenly through the length and breadth of the stone, giving the whole gem an interior glow that is very homogenous."

"[Retailers are] definitely amazed at the brilliance they see in the stone," says Eric Braunwart of Columbia Gem House, which has begun distributing concavefaceted stones under the name Radial Cuts". While most concave faceted stones on the market are cut individually by professional gem artists, Braunwart is working to produce concavecut gems in volume for jewelry manufacturers.

Consumers are impressed, say retailers. "Our customer reaction has been fabulous," says Wayne Light, a custom jeweler in Sedona, Arizona, who offers his customers oneofakind stones by Arizona gem cutter Larry McCoy. "They're enthralled with the look of the concave faceting. It's probably been one of the hottest new looks we've had."

In addition to its sparkle, concave faceting improves body color in lighttoned stones, helps hide inclusions, and reduces or even eliminates windowing effects resulting in a more salable gemstone.

"The most important thing [to consumers] is the color," says Troy Steckenrider of upscale retailer Molina in Phoenix ' Arizona . "We've always found that [to be true], whether it's tanzanite or Kashmir sapphire or Burmese ruby. When you have the addition of this increased sparkle [through concave faceting], we see a much higher acceptance, and price has never been a question."

Yet despite their advantages, concavefaceted gemstones aren't likely to push traditionally flat faceted stones off center stage any time soon.

For one thing, only certain types of gems benefit from concave faceting: Larger gems demonstrate greater brilliance with this technique than smaller ones, and light to medium toned stones are more dramatically improved than highly saturated gems, which may even look darker and less attractive when concave faceted.

Concave faceting also results in approximately 10 percent greater material loss than traditional faceting techniques, making it most appropriate for less expensive gem materials that are readily available in larger sizes. The gems most commonly being used in concave faceting are aquamarine, citrine, amethyst, tourmaline, peridot, spinel, and golden beryl.

The higher weight loss in concave faceting also increases the price of these gems, as does the additional labor required to cut a gem using this technique. "There's a lot more labor to do this than standard cutting, so as a result stones are more expensive," says McCoy. McCoy's oneofakind works of art range from $150 to $40,000 per gem, while Homer's concavefaceted gems typically cost $200 to $500 more than a comparable, traditionally faceted gem.

That additional cost does limit the market, notes cutter Mark Gronlund of Enterprise, Florida . "This type of cutting is not for everyone," he says. "There are people out there looking for price per carat," and concave faceted stones are not competitive when compared strictly on price.

Price also tends to determine the materials gem cutters work in. "A larger stone shows off the cutting better than a smaller stone, and by working in [quartzes, beryls, and tourmalines], it's still somewhat affordable," says Gronlund. "If we did that work on, say, sapphire, with a 15 or 20carat stone, [the price would be extremely high, and] there's just such a small market for a stone of that price range."

The market may be limited, but current demand remains greater than supply. "We've been sold out for months," says Braunwart. "Right now we've put a cap on sales, and only people currently buying from us can get [Radial Cut gemstones].

We're not offering [them] to new manufacturers, because it appears that the few manufacturers we are selling to are growing their sales as rapidly as we can grow production."

Despite rising demand, the skill and time required to cut gemstones using concave faceting has so far discouraged large, overseas cutting factories from venturing into the arena.

"To mass produce [concavefaceted gems], you would have to train cutters overseas to extreme subtleties," observes Homer. "I don't know that's possible, given all the variables.

Concave faceting is not something you can easily write out a recipe for. It's a handson artist kind of thing, not a thing you can crank out on an automated machine."

"In hindsight, I would never have done it if I knew how much work it would take," admits Braunwart candidly. "It's not a simple thing to do in production. It's hard, it's slow, and you have to convince cutters used to working piecework that they're going to make more not working piecework if they only produce three or four stones a day. Then there's the different varieties of machines that had to be built and rebuilt [to get the results we wanted]. I think most people would abandon [the effort] long before they got into production."

As a result, concavefaceted gems are not readily available in large quantities, and will probably never put in an appearance on television shopping channels or the counters of volume retailers. Yet that very scarcity is proving to be a selling point.

"There's a great need and interest for jewelers to set themselves apart from other large, massproduction operations, such as the Internet and television [retailers]," says Homer.

"Concave faceting is ideal for independent designers and independent jewelers looking to bring people into stores with merchandise that is different from the things that can be obtained from the Internet or their TV set."

"In this industry, everyone is looking for something new and different to offer customers," observes McCoy. "We work with custom jewelers more than anyone else, because they want to offer more unique pieces to their customers. The jeweler running a 50percentoff sale is not likely to be our customer [concavecut gems are] really designed more for people who want unique things."

But even if concave faceting turns out to be an item for the connoisseur rather than the masses, it appears to be here to stay. "This increases the brilliance of a gemstone significantly, and for people willing to pay for it, I don't think it's a fad," says Braunwart. "De Beers has driven sparkle into everybody's mind. Everybody wants stones that sparkle more, and these do."

"My dad was told it was a fad that would disappear," observes Zane Hoffman, Douglas Hoffman's son and current president of PolyMetric Instruments. "I don't see that happening. I believe it's here to stay, and I think it's going to grow. There are so many different things that you can do with it, that it's just endless the designs you can create with it."
How it Works
How does concave faceting create so much more brilliance than regular flat faceting? Imagine a typical flat, square mirror, Now push the top and bottom closer together so that the reflective side curves toward you. Than take the left and right edges and curve them away from you so that the whole thing is slightly cylindrical.
The result would be shaped like a single pavilion facet in a concave faceted gem.
If you were to shine a light on the curved mirror's surface, it would act more like a mirrorball than a flat mirror, scattering light away from it in all directions rather than a single beam. In a faceted stone, that reflected light in turn bounces off other facets, and the scattering effect is magnified.
Because the reflected light is diffused rather than concentrated in a single beam, the body color of a pastel gem doesn't get washed out. Conversely, in a gem with a dark color, the reflected light isn't strong enough to illuminate the interior of the gem, and the stone appears darker than it would with flat faceting

By Suzanne Wade
© Colored Stone – 2000
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Suzanne Wade

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