New casting method to make 5th official state seal

The Public Administration and Security Ministry said Thursday that a new casting method will be used for the fifth state seal in making public the handle and letters of the seal.

The fourth seal was scrapped last year after corruption was exposed involving the head of the seal’s production. The incident proved that the traditional wax casting method that had allegedly been around for hundreds of years was non-existent.

Lee Soo-gil, senior deputy director of the ministry, said the design of the new seal will be selected through competition and its casting method will be chosen to suit gold.

Experts say lost wax casting can replace the method using wax. Lost wax casting has developed from wax casting and is mainly used in making jewelry. While the latter uses wax to make a model and soil to make a mold, the former uses artificial wax and gypsum.

Under the lost wax casting, a model made of wax is wrapped in gypsum and baked. Gypsum then gets hardened and wax melts away. Molten iron is poured into the remaining gypsum mold, which is then destroyed when iron cools.

Doh Jeong-man, a senior researcher at Korea Institute of Science and Technology who headed production of the third state seal, said, “The new seal is likely to be made using lost wax casting,” adding, “It is conventional because it inherited a traditional method.”

Ordinary casting methods allow mass production by repeatedly using the same molds but cannot create fine and sophisticated items.

Hong Joon-pyo, a material sciences and engineering professor at Yonsei University, said, “Unlike ordinary casting, lost wax casting makes customized molds to create delicate sculptures,” adding, “The method suits the artistic value of the state seal.”

Under lost wax casting, however, the volume of an artwork changes when molten iron cools down. The change in volume creates empty space inside the artwork and reduces its strength, requiring technology that gives consistent pressure until molten iron cools completely.

wonc@donga.com