Cloisonné, an ancient metalworking technique, is a multi-step enamel process used to produce jewelry, vases, and other decorative items. (The resulting objects can also be called cloisonné.)

History

Cloisonné first developed in the Near East. It spread to the Byzantine Empire and from there along the Silk Road to China. Chinese cloisonné is arguably the most well known of all the varieties of cloisonne and enamel making. Russian cloisonné from the Tsarist era is also highly prized by collectors. Chinese cloisonné is sometimes confused with Canton enamel, a similar type of enamel work that is painted on freehand and does not utilize partitions to hold the colors separate.

Cloisonné process

1. Body-making. the artist forms metal (such as copper, bronze, or silver) into the shape of the finished object. The material usually used for making the body is copper, since it is easily hammered and stretched.
2. Filigree-soldering. which is pure silver wire usually about .010 x .040 inches in cross section, is bent into shapes that define the colored areas. The bends are all done at right angles, so that wire does not curve up. This is done with small pliers, tweezers, and custom-made jigs. The cloisonné wire pattern may consist of several intricately constructed wire patterns that fit together into a larger design. Solder can be used to join the wires, but it causes the enamel to discolor and form bubbles later on. Instead, the base metal is fired with a thin layer of clear enamel. The cloisonné wire is glued to the enamel surface with gum Tragacanth. When the gum Tragacanth has dried, the piece is fired again to fuse the cloisonné wire to the clear enamel. The gum Tragacanth burns off, leaving no residue.
3. Enamel-filling. The basic elements of enamel are boric acid, saltpetre and alkaline. Due to the difference in the minerals added, the colour differs accordingly. Usually one with much iron will turn grey, with uranium, yellow, with chromium, green, with zinc, white, with bronze, blue, with gold or iodine, red. In time of filling, all the colours, ground beforehand into minute powder and contained in plates, are placed in front of the workers and are then applied to the little compartments separated by filigree.
4. Enamel-firing. This is done by putting the article, with its enamel fillings, to the crucible. The enamel in the little compartment will sink down a bit after firing. That will require a refilling. This process will go on repeatedly until the little compartments are finally filled.
5. Polishing. Some pieces of hard carbon are used for polishing to produce some lustre on the surface of the article.
6. Gilding. The article is placed in fluid of gold or silver. The exposed parts of the filigree and the metal fringes of the article will be smoothly and evenly gilded. Alternatively, the exposed metal is electroplated with a thin film of gold to prevent corrosion and to give a pleasing appearance.