Trends & Fashion
The Art of Granulation
Granulation is a complex metalworking technique created by goldsmiths to adorn or enhance jewelry or decorative objects. Unrelated to any other jewelry-making technique, granulation is based on the “joining process,” a method of applying small, usually round balls, or granules, to a base. This is a difficult process because the temperature of the metal has to be hot enough to achieve fusion; in order to achieve this successfully, high–karat gold or metal alloys are employed.
The word granulation comes from the Latin word granum meaning “grain.” Granulation was a technique first thought to be founded by the Sumerians (in what is present day Iraq), but research also has uncovered evidence of granulation as far back as the third millennium B.C. Granulation was later adopted by the Etruscans (Italy’s earliest civilization) who perfected fine powder granulation. Granulation techniques were also used in Egypt and Greece.
For many years, the art and technique of granulation almost was forgotten; however, Italian jeweler Fortunato Pio Castellani's relationship with his good friend Michelangelo Caetani, Duke of Sermoneta, and a noted archeologist, inspired Fortunato and his two sons to reproduce ancient gold metal work from archaeological discoveries of the time. The Castellanies were able to study the techniques of soldering to uncover the method of fabrication for granulation. The Castellanies kept the granulation techniques a secret within the family for many years, and then started a goldsmithing practice in order to reproduce the finest ancient jewelry adorned with granulation. Today, much of the Castellani jewelry is still traded around the world by collectors, dealers and museums.
The Granulation Process
Granulation begins with a process by which wire is cut into short-length pieces, which are then processed into tiny spherical balls of precious metal alloys. These granules are then used to create a design or pattern on a piece of metal to help enhance or decorate the designed piece.
Many different methods exist to enable goldsmiths to make granules. One way is to take a thin sheet of precious metal, cut it into 1 mm. square paillons, and then coat them with layers of charcoal to prevent the paillons from sticking together during the firing process. The paillons are fired in a casting furnace until the metal reaches the desired temperature, and the paillons form the spherical or granular shape needed for the design. The granules are then cooled and cleaned either in water or a pickling solution. At this point, the granules are ready for the next step in the process: adhesion to a piece of jewelry or metal object for decoration.
Another way is to take tiny pieces of high-karat thin gold wire (or other precious metal) and cut it into small pieces. The pieces are then heated until they ball up into gold spheres which are then used to make a design or border for a fine piece of jewelry.
A third method is to place droplets of melted metal into cold water. After the metal cools, the goldsmith then sorts the granules into groups by size. In order to create a design, goldsmiths or metal handlers use an adhesive plant sap from the Tragacanth shrub (native to the Middle East) to attach the granules to the metal design.
Ancient Soldering is the process by which the goldsmiths would make solder from the same pieces of precious metal as the objects to be joined, or from an alloy of gold and at least 40% silver to ensure that the granules would have a lower melting point than that of the metal to which the granules were going to be attached.
Separate or point granulation is the process by which there is no bonding of one granule to another; each granule is placed on a piece separately. This method is primarily used for decorating metal wires.
Linear granulation is the process by which the granules are arranged in lines and are usually set in grooves or indentations within metal. Linear granulation is rarely applied to a smooth surface directly.
Field granulation, also called Massed granulation, is the process by which granules are packed together in what appear to be sheets of granules, then joined or soldered to the metal object or piece of jewelry.
Cluster granulation, also known as Grape-like granulation, is the process in which three-dimensional clusters are assembled on the jewelry or piece of decorative metal by bonding granules together.
To affix the granules of gold or precious metal in place, different methods of soldering can be used, such as:
Hard soldering, whereby two pieces of metal are soldered together by capillary action, which is achieved by lowering the melting point between the two different metals. This becomes very difficult when the entire surface needs to be decorated with granules.
Fusing is when a goldsmith uses two metals with the same alloy to create an even heat distribution, allowing the metals to begin melting together at the same temperature. This technique requires practice in order to perfect the skill because no flux or solder remnants should remain on the artifact.
Colloidal soldering, or chemical soldering, is a technique that utilizes a mixture of tragacanth gum and copper salts to lower the melting temperature of the two metals being soldered. The copper diffuses into the two metals creating a strong metallic bond. This method is also known as Eutectic Soldering.
Fusion welding is employed through the recent invention of the Laser Welder. With this technology, goldsmiths can fuse granule designs directly on a piece of metal with hardly any preparation or effort.
As observed in the archeological evidence left behind by many ancient societies, granulation has been present in jewelry or other ornate metal since the beginning of early civilization. Presently, the art of granulation still exists and is practiced in various countries around the world. As new technology and equipment is developed, making the granulation process easier, granulation may become a skill that is more readily practiced by goldsmiths and jewelers. Indeed, while the methods and techniques of granulation have evolved over time, the ornate beauty and detail of granulation remain timeless.