Treatment of Guanyin, Bodhisattva of Compassion, Chinese, Jin dynasty, about 1200:
The first step of the conservation process involves taking a series of X-radiographs to understand the sculpture’s construction. X-radiographs are images (graphs) taken with x-rays, like photographs are images taken with light (photo). As with human bodies, X-rays can penetrate wood, looking all the way through an object to see the internal structure (or bones) of the sculpture. Conservators are checking whether the figure is hollow or solid, how many pieces of wood were used in the construction, and how the various sections are joined. It is also possible that there are hidden compartments inside the figure that might house sutras or relics.
It can be difficult to take radiographs of a large and complicated object, especially one such as Guanyin with its delicate surfaces. Each image plate is 14 by 17 inches, so no one image shows the whole sculpture. Here one of the conservators is aligning the X-ray plate behind Guanyin’s head.
Most prominent in the following X-radiograph of the head is the dozens of nails used to attach the decorations of the crown. The nails are metal (hand-forged iron), which is denser than wood and appear bright white in the image because the X-rays cannot pass through them. Even without X-rays, the heads of the nails can be seen projecting from the crown, but the X-radiograph shows how deeply they go into the head.
The wood grain is also clearly visible in this image. The rings of the wood are quite wide, represented as alternating dark and light vertical lines throughout the X-radiograph.
Some of the jewelry and the body of the small Buddha figure in the center of the crown are not wood, but are formed with different material. They have not been identified yet, but look to be papier-mâché or fibrous putty.
Perhaps the most interesting thing about the X-ray below is what it reveals about the Guanyin’s eyes, which are made from small glass beads. The black beads appear lighter than the wood in the radiograph because the glass contains lead. The darker vertical lines in the center of the pupils, which look like cat’s eyes, are the threading holes in the beads.
Dozens of X-radiographs are taken for a complete look at the construction. The sculpture is solid (no hollows or hidden compartments are found) and had been carved in five main sections (more on this to come). The main section includes the head and torso, while the arms and legs are added on and attached with dowels. It is interesting that there is not one type of dowel used at the join. Some dowels have usual features such as stepped ends. In the image below, the red arrows point to two dowels at the join in the sculpture’s left thigh that also include wedges, which serve to make them fit tightly. The familiar outlines of modern nails are also evident in this image; these are from modern repairs made in the twentieth century.