Gilt-bronze Buddhist sculptures are first cast in bronze and then coated with a thin film of gold. They have been produced since the first century A.D. across all areas of Asia, including the countries of Central Asia and Southeast Asia, India, China,...
Gilt-bronze Buddhist sculptures are first cast in bronze and then coated with a thin film of gold. They have been produced since the first century A.D. across all areas of Asia, including the countries of Central Asia and Southeast Asia, India, China, Korea, and Japan, where Buddhism flourished. One can, therefore, better understand the spatial and temporal characteristics of these Buddhist sculptures when their materials and production methods are carefully analyzed through employing scientific methods and identifying the stylistic conventions with the naked eye. The gilt-bronze pensive bodhisattva, also an example of a gilt-bronze Buddhist sculpture, was also produced by means of the conventional method, yet it required a more complex and elaborate method due to its unique posture. Two pensive bodhisattva images, respectively designated as National Treasures no. 78 and 83, are the finest examples of gilt-bronze Buddhist sculptures in Korea. They have been examined with nondestructive XRF, γ-ray imaging, and 3-D scanning, and revealed the specific production method, identifying their primary features.
Two primary methods of bronze casting were used in ancient times: “piece-mold casting,” which originated in China and was used mainly in East Asia; and the “lost-wax casting,” which was developed in the Anatolian Plateau, Turkey, or in the Middle East, and spread across regions in North Africa, Europe, and Asia.
National Treasures no. 78 and no. 83 were cast with the lost-wax casting method using core pins. However, the two demonstrate distinction in terms of the method of making the core, covering wax, and carving the surface.
For National Treasure no. 78, a separate clay core was made for the head and body, and each was covered with a layer of wax, roughly carved to give the statue its basic form. The head and body were then joined into a single assemblage. Wax was additionally applied where necessary and details were carved to complete the wax mold. Two metal cores that have been hammered through the shell of the head and body indicate that they were separately made, and molten bronze permeated into the crevice of the neck created a rough protrusion on the inner neck. The use of a thin wax reduced the volume of the body of the drapery folds and ornamentation, thereby yielding an overall flat impression.
For National Treasure no. 83, a clay core was formed in a single assemblage for the head and body. The core was covered with a thick wax layer, which was carved away little by little to complete the wax mold. A single metal core extends from the head to the body. The bronze shell of the statue is fairly thick and the drapery and ornamentation are voluminous.
Extremely fine clay was used to construct the core for National Treasure no. 78, and thus the air trapped inside the wax was not effectively released when the molten bronze was poured in. This consequently resulted in a thin bronze shell, low liquidity of the molten bronze, and ultimately a number of cast defects. These flaws were remedied through an advanced technique that involved re-casting the flawed parts and attaching them to the body, or by pouring additional molten bronze to the defected area. Accordingly, National Treasure no. 78 appears to be impeccable on the surface. On the other hand, National Treasure no. 83 eliminated, from the beginning, the factors that could have led to cast defects, including securing a consistent thickness in its wax model so that the molten bronze could be poured in easily and using coarse clay for the core that allows for the efficient release of air. Although bronze alloy with less than five percent tin content was used for both statues, National Treasure no. 83 may thus be considered superior in terms of casting technique, given the efficient elimination of trapped air, the enhanced flow of molten metal, and the judicious placement of the core pins to securely stabilize the clay core.