The Buddha Statue Model Making and Casting
The model making and casting of the Buddha statue are classified in Thailand’s Chang Sip Mu (Ten art and craft categories). It belongs to the casting category, and it also involves model making--which is classified in the sculpture category. The two processes are related because a model or a sculpture must be made before the casting process can begin.
The Thai traditional methods of model making and lost-wax casting of the Buddha statue are as follows:
Model making - The model making starts from making the core of the model, which is made of sand and clay mixture. The next step is to make V-shaped channels - the main one with its branches - for pouring in the molten metal to replace the wax. A layer of Din Mom or clay mix - a mixture of ash, clay, and water - is then applied to coat the core and strengthen it. This is followed by the Tha Thueak process whereby a coat of viscous liquid - viscous liquid - a mixture of beeswax and thick rubber oil is applied. Finally, wax is applied in the Khao Khi Phueng or wax coat process, which involves forming the wax coat that will serve as the original model and will look exactly like the desired cast. This wax sculpture is modeled in fine details and chased. It will become the mold cavity to be filled with the molten metal.
Mold making - The process begins with the application of Din Nuan (clay mixed with cow dung and water) on the wax figure. Three coats are required and each time the coat must be left to dry thoroughly before applying the next coat. Metal pins are then inserted through to the core model in order to stabilize the mold cavity. Vents are attached for wax removal. Din On - Din Nuan mixed with fine-grained sand and water - is applied to coat the figure which has been fixed with pins and vents for wax to pour out. This forms the first layer, which is coated over with a slightly thicker layer of Din Kae - a mixture of clay, fine grained sand and water to form the second layer of coat. Metal wires are then strapped in a mesh-like fashion to protect the mold from the pressure that will build up inside when the mold is heated, which might crack and break the mold. The second layer of Din Kae is then applied to cover the wire strapping and the mold is left to dry for four to seven days. Then Pak Chok (pouring cups or pouring basins) and Ru Phut (vents for gas generated during the pour) are made.
Lost Wax or Investment Casting - The process begins Lost Wax or Investment Casting - The process begins with Lom Hun or moving the mold to the area where metal pouring will take place and followed by Khuen Thon or flipping the mold. Scaffolding is constructed and a channel for receiving the melting wax is fixed in place. The mold is then heated to remove the wax. The metal is melted in a crucible and poured into the mold cavity. When the metal cools down and solidifies, the mold is destroyed and the wire strapping is removed. The metal figure is chased and blackened or applied with lacquer coat and gilded.
The Thai traditional method of model making and casting of the Buddha statue reflects the folk know-how in appropriately selecting the local materials and the unique method of casting hollow sculptures with fine, thin shell. The Buddha statue model making and casting is therefore considered a highly valued religious art and craft and has contributed to perpetuation of Buddhism in Thailand.