Date Published: March 15, 2017
Publisher: Public Library of Science
Author(s): Yunbing Zong, Shengkun Yao, Jianfeng Lang, Xuexiang Chen, Jiadong Fan, Zhibin Sun, Xiulan Duan, Nannan Li, Hui Fang, Guangzhao Zhou, Tiqiao Xiao, Aiguo Li, Huaidong Jiang, Gayle E. Woloschak.
Casting had symbolic significance and was strictly controlled in the Shang dynasty of ancient China. Vessel casting was mainly distributed around the Shang capital, Yin Ruins, which indicates a rigorous centralization of authority. Thus, for a casting mold to be excavated far from the capital region is rare. In addition to some bronze vessel molds excavated at the Buyao Village site, another key discovery of a bronze vessel mold occurred at Daxinzhuang. The Daxinzhuang site was a core area in the east of Shang state and is an important site to study the eastward expansion of the Shang. Here, combining synchrotron X-rays and other physicochemical analysis methods, nondestructive three-dimensional structure imaging and different elemental analyses were conducted on this mold sherd. Through high penetration X-ray tomography, we obtained insights on the internal structure and discovered some pores. We infer that the generation of pores inside the casting mold sherd was used to enhance air permeability during casting. Furthermore, we suppose that the decorative patterns on the surface were carved and not pasted onto it. Considering the previous compositional studies of bronze vessels, the copper and iron elements were analyzed by different methods. Unexpectedly, a larger amount of iron than of copper was detected on the surface. According to the data analysis and archaeological context, the source of iron on the casting mold sherd could be attributed to local soil contamination. A refined compositional analysis confirms that this casting mold was fabricated locally and used for bronze casting.
The origin of the Bronze Age in China may date back to the Majiayao culture [1,2], whereas the fabrication and use of bronze vessels prevailed in the Shang dynasty . In northern China, many bronze vessels have been discovered around Yin Ruins, the capital of the later Shang dynasty [4,5]. Bronze vessel production seems to have been concentrated in the capital region and that these reported in the paper are the first vessel casting mold remains discovered outside of Anyang for the Anyang period [6,7]. In 2007, several bronze molds and vessels were excavated at the Buyao Village site [8,9]. Bronze vessels were highly significant markers of status and crucial media for ritual communication with the ancestral powers, and so the discovery of mold fragments outside of the Great Settlement Shang is highly significant.
The casting mold sherd in this study comes from the Daxinzhuang site, which is located in the eastern part of Shang state. Although large amounts of bronze wares have been excavated here, few casting molds have been found. Importantly, a piece of casting mold with fine decoration was obtained. The casting mold sherd (sample number: 2010DXZJ9T2024H900②:18) was excavated in pit H900 at Daxinzhuang site and other remains including pottery sherds and animal bones were also excavated (S1 File). We infer that it is a vessel casting mold sherd from the arc-shaped front and back (Fig 2E and 2F), because the molds used to create bronzes with a shape of cambered surface. To confirm the age of the casting mold sherd, a pig bone found in the same excavation unit was used for standard AMS-14C dating in a Beta Analytic laboratory (S1 Fig). We also collected and studied the excavated pottery pieces that were made in local styles of the Daxinzhuang site to confirm the elements that are present in the casting mold sherd (S2 Fig).
In this work, we investigated one casting mold sherd that was excavated from Daxinzhuang. The standard AMS-14C dating confirms that it is a mold from the Shang dynasty. The nondestructive X-ray structural and technological analysis shows that this casting mold was carefully designed for casting. The pores that were discovered inside indicate that the people at the time were aware of the air permeability issue for casting molds. The three-dimensional structure analysis also shows that the decorated patterns on the surface were carved into the mold. Comprehensive elemental analysis methods combined with other excavations in Daxinzhuang prove that this mold was made locally and used for bronze vessel casting. By referring to previous excavations of objects connected with the royal capital, such as bronze articles, jadeware and oracular bones, the casting mold sherd could verify that the Daxinzhuang site was an important regional center in the late Shang state. This clue helps archaeologists to understand the cultural prosperity that was downstream of the Yellow River 3,000 years ago. However, more excavations will be helpful and necessary to reveal more details about the expansion of the late Shang state.