Early Gemstone Cutting Techniques
During the middle ages the most common cut was the cabochon, with a convex upper surface, these stones were far from anything technical in the art of gemstone cutting. These stones were usually coloured stones, such as garnet, amethyst, or more scarcely, sapphire or ruby. It was during the fourteenth century that more complicated techniques of lapidary came to materialise in the form of facets.
Firstly, in order to create facets on a gemstone a flat surface is required - a simple rectangular shaped gemstone is needed. Most often, an existing cabochon stone would be re-cut, or an unaltered diamond in its natural state (termed a ‘point cut’), would be first flattened by the simple expedient of cleaving off the top ‘dome’ or ‘point’ to create the flat surface, then with additional planes cut into the surface of the stone - the ‘table cut’ was formed.
Benvenuto Cellini’s disquisition on goldsmithing and sculpture (first published in 1568) imparts on stone enhancement techniques; such as metal foiling and the allusion of ‘lamp-black’ varnishing, a practice that long continued into the 17th century, evidenced in contemporary portraits, with the subject adorned in jewels, adduced by Cellini as the table, the pointed and the faceted cut gemstone. The last to be noted, the rose-cut; often a diamond, usually an irregular shaped cabochon with a puzzle of triangular facets covering the surface, this particular cut, together with the 17th century brilliant-cut, has, with proclaimed modifications, remained increasingly popular today.
- Lamp-black: The underside of a diamond receives a coat of pure carbon pigment, the residual soot from burning oil - coined from the practice of making it with oil lamps
- Foil back: Layering a thin piece of metallic foil onto the back of a stone
- written by Sammy