Cloisonné wire is made from pure silver or gold and is usually about .010 x .040 inches in cross section; brass and occasionally copper can also be used. It is bent into shapes that define the colored areas. The bends are all done at right angles, so that the 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 this causes the enamel to discolor and form bubbles later on.
Most existing Byzantine enamels have soldered cloisons, however the use of solder to adhere the cloison wires has fallen out of favor due to its difficulty, with the exception of some "purist contemporary enamellists" who create fine watch faces and high quality very expensive jewelry. Instead of soldering the cloisons to the base metal, 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 has dried, the piece is fired again to fuse the cloisonné wire to the clear enamel. The gum burns off, leaving no residue.
Vitreous enamels in the different colors are ground to fine powders in an agate or porcelain mortar and pestle, then washed to remove the impurities that would discolor the fired enamel. Each color of enamel is prepared this way before it is used and then mixed with a very dilute solution of gum tragacanth.
The vitreous compound consists of silica nitre and lead oxide to which metallic oxide is added for coloring. Using fine spatulas, brushes or droppers, the enameler places the fine colored powder into each cloison.
The piece is left to dry completely before firing, which is done by putting the article, with its enamel fillings, in a kiln. The enamel in the cloisons will sink down a lot after firing, due to melting and shrinkage of the granular nature of the glass powder, much as sugar melting in an oven. This process is repeated until all cloisons are filled to the top of the wire edge.
Three styles of cloisonné are most often seen: concave, convex, and flat. The finishing method determines this final appearance.[18] With concave cloisonné the cloisons are not completely filled. Capillary action causes the enamel surface to curve up against the cloisonné wire when the enamel is molten, producing a concave appearance. Convex cloissoné is produced by overfilling each cloison, at the last firing. This gives each color area the appearance of slightly rounded mounds.
Flat cloisonné is the most common. After all the cloisons are filled the enamel is ground down to a smooth surface with lapidary equipment, using the same techniques as are used for polishing cabochon stones. The top of the cloisonné wire is polished so it is flush with the enamel and has a bright lustre. Some cloisonné enamel is electroplated with a thin film of gold, which will not tarnish as silver does.
