Professional Jeweler Archive: Gemstone Flashdance

July 2001

Gemstones & Pearls/News

Gemstone Flashdance

Signity introduces matched cabochons, some of which are foil-backed

Signity’s decision to add a line of precisely matched cabochon-cut gemstones comes as welcome news for gem setters and designers. That’s because calibrated goods are not always perfectly calibrated. They often have irregular girdle outlines, different heights, irregular cabochon domes and varying colors or qualities of gem material. In practical gem setting, getting a piece of jewelry to look uniform becomes a challenge, with the gem setter having to search though many stones to find a perfect match.

Signity, of Horgen, Switzerland, is out to change that with its new precision-cut lines called Flash Cabs and Regular Cabs. The gemstones complement Signity’s existing lines of precision-cut faceted goods and are available in round (2mm-4mm) and oval shapes (5mm by 3mm and 6mm by 4mm) in amethyst, citrine, peridot, rhodolite, white topaz and blue topaz.

Revisiting Foil-Back

The Flash Cabs are foil-backed, a process in which their flat bottoms are coated with a proprietary substance designed to increase their brilliance. Foil-backing creates a reflective surface and results in the reflecting and refracting of light and color back to the viewer. “It is important to note we have applied this back to our lighter colors only,” says Harald Winzer, managing director of Signity in New York City. “Our darker shades do not have the foil backing.”

Most faceted gems don’t require this enhancement because they return light and color so effectively through the crown and table facets. Cabochon-cut gemstones, with smooth rounded tops and flat bottoms, are naturals for the process. All of Signity’s printed literature fully describes the enhancement and its effects so jewelers can properly disclose the technique to customers.

Flash Cabs’ “new look” is designed to dazzle. But the technique of foil backing gems dates back hundreds of years, though it hasn’t been used much recently. Italian metalsmith Benvenuto Cellini described the laying of a reflective surface beneath a flat-bottomed diamond as early as 1568.

Care Considerations

Signity’s suggestions for jewelers working with Flash Cabs are as follows:

  • While working with the stone, temperatures should not exceed 180&Mac251; C.
  • Ultrasonic cleaners’ wavelength should be set higher than 40kHz.
  • No acids or solvents should be used in the ultrasonic cleaners. It’s preferable to clean these gems using a soft cloth and soapy water.

Signity New York Ltd., New York City; (866) 221-8234,

– by Robert Weldon, G.G.

Calibrated cabochons by Signity provide jewelers with a new standard in precision cuts. This photo shows the Regular Cabs line of amethyst, citrine, peridot, rhodolite, white topaz and blue topaz. Photo by Robert Weldon
Flash Cabs are foil-backed cabochons. The foil backing enhances brilliance and color and is reserved for the lightest gems. Flash Cabs make up a smaller portion of the entire cabochon program at Signity. Photo by Robert Weldon

Copyright © 2001 by Bond Communications