Gold on Gold: Techniques in Granulation

Estate Citrine Drop Earrings with Granulation. Photo ©2014 EraGem Jewelry. These inspired earrings are evocative of the Etruscan period of jewelry, with their exquisite square-cut natural citrine center stones, their brushed gold finish, and especially with their decorative granulation in 18k gold. Artisans working between 700-500 BC resurrected many of the ancient techniques in jewelry and art, including filigree, milgrain, and granulation. Granulation is a beautiful technique which is used to create mosaic-like patterns out of tiny spheres (granules) of gold. Granulation takes a tremendous amount of time and effort, especially when an entire surface is covered. Each tiny bead of gold is individually formed and individually placed and affixed to the surface of the jewel. In this case, the pattern is fairly simple, an edging of the raised bezel surrounding the stone with equally spaced flourishes along the center and corners of the sides. However, many of the most popular antique pieces featuring granulation are completely covered in tiny beads, representing hours of intense labor. This work is done by hand using a number of adhesion techniques. One such technique is hard soldering, where a hand-soldering tool is used to warm the point of contact between each granule and the surface of the jewel. This is the most laborious and least often used method in fashioning granulated jewelry. A variation of this technique is more often used, in which a portion of gold is filed into powder and mixed with a flux agent (tragacanth gum). By itself, the flux agent is also used to paint the surface of the piece, leaving a thin layer into which the jeweler can embed the tiny beads of gold. After the beads are set in place, the flux-solder mixture is then sprinkled over the entire surface and heated to its melting point. This process does leave a residual puddling of metal around each bead, which is unavoidable. A second method is called fusing. In this technique, metals of the same alloy are fused together by heat alone. A thin sheet of metal the approximate thickness of the granules is painted with a thin layer of diluted flux. The granules are carefully placed in the intended pattern, and then the whole segment is placed in a reducing oven (little or no oxygen present). Once the metal reaches its melting point, the granules and the sheet metal fuse together at their points of contact. The reductive atmosphere eliminates all excess flux and solder, preventing the puddle effect seen in hard soldering. Once the piece has cooled, it can be formed into the desired shape for the finished jewel. Some believe this is the method the Etruscans used to perfect their practice; however, others believe the Etruscans used another method, colloidal (eutectic) soldering. With colloidal soldering, a carefully prepared mixture of tracaganth gum (or possibly fish paste or cowhide glue in the case of antiquity) and copper salts is applied to the sheet of metal in order to reduce the required temperature for melting the base and the granules. The thin metal sheet is painted with the colloidal solder, and a fine paint brush is used to position the granules. After the surface dries completely, the piece is fired in a reducing oven until the flux agent burns off completely. As it burns, it releases the copper salts into the points of contact. Once the oven reaches 890 degrees Celsius, the copper diffuses into the granule and the base, forging a powerful metallic bond between the two. Regardless of which method is used, granulation requires a tremendous amount of skill, precision, and patience. It's no wonder that the results are dazzling.