Jingtai blue commonly refers to copper-bodied cloisonne enamel. Craftspeople shape metal wires into design boundaries, fill the compartments with enamel, and fire and finish the piece. The name is traditionally associated with the Ming Jingtai reign, but the craft's history and later development span several periods. Its colors are not confined to blue.
Historical background
Cloisonné is an ancient technique for decorating metalwork objects with colored material held in place or separated by metal strips or wire, normally of gold. In recent centuries, vitreous enamel has been used, but inlays of cut gemstones, glass and other materials were also used during older periods. Cloisonné enamel was probably developed as an easier imitation of cloisonné work using gems. The resulting objects can also be called cloisonné.
The decoration is formed by first adding compartments (cloisons in French) to the metal object by soldering or affixing silver or gold as wires or thin strips placed on their edges. These remain visible in the finished piece, separating the different compartments of the enamel or inlays, which are often of several colors. Cloisonné enamel objects are worked on with enamel powder made into a paste. The objects are fired in a kiln for finishing. If gemstones or colored glass are used, the pieces need to be cut or ground into the shape of each cloison.
Ancient world
Cloisonné first developed in the jewellery of the ancient Near East, and the earliest works with enamel all used the cloisonné technique, placing the enamel within small cells with gold walls. This had been used as a technique to hold pieces of stone and gems tightly in place since the 3rd millennium BC, for example in Mesopotamia, and later in Egypt. Enamel seems likely to have developed as a cheaper method of achieving similar results.
The earliest surviving undisputed objects known to use enamel are a group of Mycenaean rings from a tomb in Cyprus, dated to the 12th century BC, which used very thin wire.
In the jewellery of ancient Egypt, including the pectoral jewels of the pharaohs, thicker strips form the cloisons, which remain small. In Egypt gemstones and enamel-like materials (sometimes called "glass-paste") were both used. Although Egyptian pieces, including jewellery from the Tomb of Tutankhamun of c. 1325 BC, are frequently described as using "enamel", many scholars doubt that the glass paste was sufficiently melted to be properly so described, and use terms such as "glass-paste".
China
From Byzantium or the Islamic world the technique reached China in the 13–14th centuries; the first written reference is in a book of 1388, where it is called "Dashi ware". No Chinese pieces clearly from the 14th century are known, the earliest datable pieces being from the reign of the Xuande Emperor (1425–35), which however show a full use of Chinese styles suggesting considerable experience in the technique. It was initially regarded with suspicion by Chinese connoisseurs, firstly as being foreign, and secondly as appealing to feminine taste. However, by the beginning of the 18th century the Kangxi Emperor had a cloisonné workshop among the many Imperial factories.
The most elaborate and highly valued Chinese pieces are from the early Ming Dynasty, especially the reigns of the Xuande Emperor and Jingtai Emperor (1450–57), although 19th century or modern pieces are far more common. The Chinese industry seems to have benefited from a number of skilled Byzantine refugees fleeing the Fall of Constantinople in 1453, although based on the name alone, it is far more likely China obtained knowledge of the technique from the middle east. In much Chinese cloisonné blue is usually the predominant colour, and the Chinese name for the technique, jingtailan ("Jingtai blue ware"), refers to this, and the Jingtai Emperor. Quality began to decline in the 19th century.
Modern process
First the object to be decorated is made or obtained; this will normally be made by different craftspeople. The metal usually used for making the body is copper, since it is cheap, light and easily hammered and stretched, but gold, silver or other metals may be used. Cloisonné wire is made from fine silver or fine gold and is usually about.010 x.040 inches (1⁄4 by 1 mm) in cross section. 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.