Cloisonne, can be broadly defined as a vitreous, glass like coating fused on to a metallic base. The technique originated in Egypt prior to 1800 B.C. when gold ornaments were inlaid with small pieces of turquoise, lapis lazuli, carnelian, garnet, and held in position by ribs soldered to the gold base. This decorative technique reached its pinnacle as a result of the efforts of Chinese artisans. Chinese cloisonn? is now the standard by which the quality and beauty of cloisonne is measured worldwide.
Cloisonne is a French word meaning to be compartmentalized, to feel cut off, or shut out; referencing the wires used in construction. Thin strips of metal are bent to form the outline of a design and fastened to the surface of a metal object, either by soldering or a coat of enamel. The resulting compartments, known as cloisons, are then filled with enamel.
The roll of cloisons as a means of keeping molten enamels separate is overstated. With the glass and firing methods available, early craftsmen actually had difficulty getting enamels to gloss out. These early enamels would only begin to fuse at temperatures exceeding 1500 degrees F. The primary function of the wires was to counter the low expansion of the early enamels, which must be less than the expansion of the metal keeping the enamel under constant compression. If the degree of difference is too great, the enameled piece will warp during the cooling process, causing the enamel to fracture.
Silver has the highest expansion rate between the three most common metals used as a base for enameling including gold and copper. The result, there is little mention of silver enameling during the early years. Gold, having the lowest expansion of the three metals and high ductility was the only possible medium for early enamellers.
Success for early enamellers was achievable only in fragments, which gives us insight as to the primary purpose of cloisons, to divide the object into a number of small enameled fragments joined by un-enameled metal. Furthermore, the cloisons reinforced the artists design, helping to reduce warping due to excessive heating and cooling, which in turn helped eliminate cracking enamel.