Granulation is the art of creating a surface pattern on jewelry with tiny balls, and dates back to the third millennium BC. The technique was invented in the Eastern Mediterranean and Egypt and later refined by Etruscan goldsmiths.
The process begins when wire is cut into short lengths and melted into round granules that are placed on the jewelry in the desired pattern. They’re held in place with a temporary glue made from plant sap. In the best examples, the balls are attached permanently with heating (which evaporates the glue), not soldering.
However, granulation is a tricky and difficult process because the temperature has to be hot enough to fuse the ball to the surface, but not enough to melt the ball into an amorphous puddle. It only works with pure silver or 22k gold, which doesn’t oxidize when heated. Oxidation would interfere with the fusing process. Granulation or fusing involves raising the temperature of both the back sheet and the granules and wires to be fused, to the point at which they melt just enough so that they will adhere permanently to one another.
It is done using a small kiln to heat the bottom of the piece while heating the top of the piece with a torch. It’s a very delicate operation. If the correct temperature is not reached, the items to be fused will not hold properly, making it necessary to reheat the whole piece and try again. If the temperature gets too high, too fast, meltdown can occur, which is irreversible.
Needless to say, much skill is needed to bring both the back sheet and the object to be fused to the appropriate temperature very slowly. The artist will see a quick “flash” in the metal, which occurs for just an instant. Granulation is a technique one must learn simply by doing. Most granulated pieces get a quick brushing with a brass brush to give them a nice buffed finish rather than a high shine.
Here’s a very interesting article that delves further into the art of granulation: http://www.jckonline.com/2015/10/21/granulation-reviving-ancient-technique*