☆Jumul refers to a mold made by melting metal and injecting it into a mold. The Gyeonggi-do designated jumuljang is a craftsman with the technique of melting iron and weaving molds to make cauldrons. Anseong Jumul is run by Kim Jong-hoon, a foundry owner. It began in 1910 when his grandfather Kim Dae-sun filled the cauldron, and in 1924, his grandfather Kim Soon-sung established a factory in Mulmun Street, Bongsan-dong, Anseong. When his grandfather became ill in 1953 and unable to operate the factory, Kim Jong-hoon, the current owner of the foundry, took over the family business; and now his son and successor Kim Sung-tae has been in charge of the operation for four generations.
The process of making a cauldron is largely divided into making an egg frame and an outer frame, and pouring iron.
Put in the finest castings first for the inner shape of the cauldron. Then, when separated from the frame, a round-shaped frame is completed. The made egg frame is dried to one side and then finely trimmed to prevent air from entering between rough surfaces, and graphite powder are applied continuously for about an hour on top of it to polish the egg frame.
The outer frame, which is responsible for the appearance of the cauldron, is made by applying soil water and using a traditional tool called "Dore." The finished frame goes through a process of heating it up to get rid of moisture. If there is any moisture left in the frame, it can explode in contact with the iron water, and the soot on the frame during the heating process is effective in making the solids hot.
Jumuljang uses iron with a carbon content of 1.7 percent or more, and a solid fuel coke is used as a fuel to melt iron. Fuel and iron work is carried out in traditional waterways, with holes for iron ingress on the first floor and a fireball putting materials on the second floor. If you put in 25 kilograms of coke, 80 kilograms of iron, and the remaining 20 kilograms (4:1 ratio), the iron will pool on the first floor. Separate impurities by adding limestone, which is the main ingredient of calcium carbonate, during seasonal work.
Put an egg frame on the finished outer frame, cover it with a lid, and prepare to inject iron. When the iron from the furnace is poured into the mold, the metal enters the gap between the frame and the inner frame and becomes a cauldron. When pouring iron, the metal stream is used to fill the inlet.
The density increases and the thickness becomes constant only when it is filled. Three minutes after pouring the iron, if the temperature of the iron drops below 800°C, separate the molds and remove the iron and casting yarn from the cast iron pot. After taming with sesame oil, the surface becomes spicy and smooth. The method of making cauldron caps is no different from the method of making cauldrons, but regardless of the size of cauldrons, cauldron lids are made at a quarter of the weight of cauldrons.
If you look at the thickness of the cauldron cross-section made like this, the thickness of the sides is about 4 to 5mm thinner than the thickness of the floor is about 9mm. Regardless of the size of the cauldron, the thickness difference between the floor and the sides is made in half. The first part that the fire touches is thick, and the last part that touches it is thin so that it is evenly delivered inside when heat is transferred. Recently, using this traditional casting technology, modern products such as frying pans and takoyaki pans have been introduced as well as cauldrons.