Bronze casting technique (clay mold bronze), a traditional technique item in the fourth batch of representative items of municipal intangible cultural heritage. Since the late Neolithic period, my country has entered the era of using both copper and stone. The early bronzes unearthed in Hebei and other places are either forged or cast, indicating that the casting technique has a long history in my country and has been developed very early. According to recent archaeological excavations, bronze was already cast in the Xia Dynasty. The initial casting molds used stone molds. Since the stone is not easy to process and is not resistant to high temperatures, with the development of pottery making, clay molds were soon used. For more than three thousand years, before the rise of modern machine manufacturing and the use of sand casting, clay molds have always been the main casting method. In the early Shang Dynasty, with the Erlitou site in Yanshi, Henan as a symbol, clay molds were used to cast small production tools such as copper adzes and copper chisels, as well as daily utensils such as copper bells and copper jugs. Later, with Erligang in Zhengzhou as a symbol, the bronze smelting industry began to develop. The two large square tripods unearthed in Zhangzhai, Zhengzhou, show that the bronze casting technology in the middle of the Shang Dynasty had reached a considerable level. From single-sided and double-sided mold casting, it developed to the ability to use multiple molds and cores to form a composite casting mold to cast large castings weighing more than 100 kilograms. For the drying, roasting, assembly of the mold core, uniform wall thickness so that it can solidify at the same time, and preheating the mold so that it can be poured smoothly, the Shang and Zhou dynasties had already explored a complete set of mature processes. my country had mud mold casting in the early Shang Dynasty, and it reached its heyday in the middle of the Shang Dynasty. Using this method, ancient craftsmen created such rare treasures as the Simuwu Ding and the Four Sheep Square Zun. However, for more than a thousand years thereafter, mud mold casting basically remained at the stage of one-time mold. It was not until the Spring and Autumn Period that multiple molds (semi-permanent mud molds) were used to cast copper tools (hoes). The use of mud molds to cast large and extra-large castings has made great progress since the Tang and Song Dynasties. The iron lion in Cangzhou during the Five Dynasties, the iron tower in Dangyang during the Northern Song Dynasty, and the big bell in Beijing Dazhong Temple during the Ming Dynasty are all world-famous huge castings. Volume 8 of Song Yingxing's "The Exploitation of the Works of Nature" describes two methods of casting large objects: one is to use multiple furnaces to pour successively (bells under a thousand pounds), and the other is to use multiple furnace troughs to pour (bells weighing tens of thousands of pounds). Under the technical conditions of ancient handicraft production, this should be said to be an ingenious process that requires skilled techniques and good organization and coordination. The steps of the mud mold casting process are divided into: mold making, turning over the outer mold, making the inner mold, combining the mold, and casting. Information source: Jiangsu Provincial Intangible Cultural Heritage Protection Center Information source: Jiangsu Provincial Intangible Cultural Heritage Protection Center