In the casting history of China, clay mold casting appeared early. By the two clay mold together, casting solid, relatively simple small tools, developed by the casting technology of multiple outer mold and one core mold, the casting of cavity container, cavity container casting success, is a key leap in casting technology. From simple gadgets to large containers, it took about 400 years. Let's still take the round ding as an example, look at its casting process changes.

Why did the early three-legged round tripod cast into conical feet? This is because only when the three feet are made into a tapered shape can the three outer feet be removed. In this period, the outsole of the ding had a "Y" shaped line, and the Angle between the three lines was 120°. Later, when craftsmen invented the method of adding one piece of the bottom and three pieces of the belly, the conical foot became the cylindrical foot. The column shape can be raised, and the shape of the tripod is more majestic and beautiful. Most of the round tripod of the late Shang Dynasty and the early Western Zhou Dynasty were products of this technique. It is characterized by a △ line on the outside of the bottom of the tripod.
Another kind of progress is from muddy casting to split casting. The so-called muddy casting is made by the whole machine in one casting. It has high requirements for technical operation, difficult to make and remove the mold, time-consuming and laborious, and low efficiency, which is suitable for the objects with simple casting structure. The casting method is to cast a certain part of the casting tool first, and then fix the first cast part to a certain part of the outer mold, and cast it as a whole by secondary casting. Or more than two parts, respectively after single casting, and then riveted, socket or welding method into a unit. Improved efficiency, more convenient casting structure more complex and mass production. Although the split casting method existed in the Shang and Zhou Dynasties, it was widely used in the Spring and Autumn period, and the muddy casting method was basically no longer used in the spring and Autumn period and after that. The two ears of the ding changed from the original straight ears to appendage ears, and the columnar feet became more powerful and beautiful animal hooves.

In addition, from the beginning of Spring and Autumn, gaskets were used extensively in the casting of tripod, and the thickness of the vessel wall was more skillfully controlled, resulting in many thin and uniform bronze vessels with walls. This phenomenon is not only on the tripod, in many containers are visible on the use of gasket traces. In the Warring States Period, the popular new techniques of metal-setting, metal-setting, gilding and chisel reflect the progress of bronze casting technology and processing technology. The appearance of the gilt process shows that human beings have completed the technology of mercury production, because the gilt process must have mercury as a carrier. The process of misplacing gold and silver has a direct relationship with the appearance of steel tools. Steel tools can be used to carve slots on bronze ware. The extensive use of this kind of steel gadgets happened in the Warring States Period. The progress of various techniques and casting techniques will inevitably leave traces on the bronze ware, which is consistent with the progress of handicraft technology in the corresponding times. The lines and gaskets we talk about are the marks left on the bronze ware when the clay mold is cast. Later, after the use of wax mold casting, the use of multiple fan, also do not need gasket, so, the trace of the fan line, gasket will naturally disappear.

So is there a fan line must be genuine? A friend once brought a bronze round tripod of the Western Zhou Dynasty to be identified. The diameter of the tripod is about 25 centimeters and the decoration is rich. There was no obvious fault to be found in the molding and ornamentation, and although I did not like the red and green rust on the surface, it was not convincing. At this time, he reminded me, "You see how clear the line is, how much to open the door." When I looked, the problem was the line. There was a line of "△" on the outside of the bottom of the tripod. The triangular pattern is not only clear, but also has the same width and width, and is straight and even, which shows that the forger is casting with wax mold, deliberately making the pattern of "△", passing it off as clay mold casting. The "△" pattern line is caused by the lax connection of several pieces of external pattern. The width and width are different and the lines are not uniform. The pattern line is intentionally cast by the wax mold method, but it has become convincing antique evidence. In addition, there is another possibility that the author of the antique ware intentionally left a little flaw, once encountered the seizure of unearthed cultural relics, can immediately prove that it is antique copper artifacts, and get away with punishment.