Manufacturing Process of
Bangjja Yugi

Bangjja Yugi requires many steps to manufacture, unlike the mold casting process, and in many cases those steps require teamwork, not just an individual craftsman. Mold casting can be done by one person who mixes the selected alloy (copper, tin, zinc, nickel, iron, gold, silver, etc.) melts it and casts it by himself. This makes mass production easier.

However, Banja Yugi requires the standard alloy ratio of 78% copper to 22% tin. Other alloys, or impurities in the alloy, will prevent proper hammering to flatten and shape the item, or will give the item other undesirable characteristics. It may break easily or thicken in the wrong places. There are 9 steps to follow to correctly complete the Bangjja process.
An apprentice or junior craftsman weighs the correct ratio of copper and tin and melts it in a melting pot. He then pours the molten alloy into an open steel mold (a Badookpan) that shapes the metal into something like a round pancake (a Badook). To prevent possible air bubbles on the surface, sawdust is sprinkled on top. For centuries craftsmen have used the sawdust, but it is scientifically proven now that sawdust decreases air bubbles which cause little holes or scars on the exterior of the final product.
If there are any holes or scars, one of the craftsmen carefully prepares the initial piece and a soldering plate to paste and solder them and repair the hole or scar. The soldering plate is a square 30 mm on each side and 12 mm thick. Charcoal powder is placed on the soldering plate, and the damaged parts are placed on top of the charcoal powder. Then the plate is heated and more charcoal powder is used as necessary so that the abnormal part becomes smooth. This is a very delicate process because timing is so important in allowing the repair to create a normal shape.
The 1st flattening evens out and partially flattens the molded alloy by hammering, and then a craftsman uses a cutter to make the piece round rather than irregular. This makes the next processes easier.
The 2d flattening widens the bronze by hammering. A second piece is placed on top of the already hammered bronze, and it is hammered. This is continued until there are 10 pieces (Badook) in one set. It takes around 4 hours to make 1 set of Badook. The purpose of putting them together is to enhance productivity. For example, one piece of bronze cools more quickly than multiple pieces, so the craftsman may have to reheat pieces in order to increase or change the shapes by hammering and clamping. Normally, 2 to 11 pieces (Badook) are worked together, depending on the product.
Separating. After flattening, a U shape is made out of the Badook set. Then the individual pieces are separated from the others.
Round shaping is the process when 7 craftsmen work together to shape the bronze into 3 dimensional round shapes (such as bowls). The master craftsman leads the other 6 craftsmen and directs when to hammer and when to heat the Badook on the fire to properly shape it. All of the workers hammer the inside of the piece. At this stage, the design of the final goods are roughly completed.
After round shaping, salt water is used to soften the surface of the Badook so that cutting is easier. Putting the product in cold water softens it for Shaping in Detail.
Final tuning is used to strengthen or straighten any twisted part, and in the case of musical instruments such as gongs or bells, to improve the sound. The craftsman hammers the bronze to adjust the sound, and the process takes long experience. Some sound experts say that by playing the gong, they can hear how difficult it was to give it that sound. And it is said that the sound reveals the craftsmans heart or spirit.
Peeling is the final stage to reveal the Bangjja color. The dark colored metal on the exterior is peeled off so that the color is pleasing and sophisticated. A turning wheel and iron are used to reveal the distinctive whitish yellow Bangjja color.