Scientific Examination of Shang-Dynasty Bronzes From

Home , Changwu County, Chenggu County, Hanzhong, Lintong District, Shaanxi, Wugong County

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Journal of Archaeological Science xxx (2009) 1–11

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Scientiﬁc examination of Shang-dynasty bronzes from Hanzhong, Shaanxi Province, China

Jianjun Mei a, Kunlong Chen a,*, Wei Cao b a Institute of Historical Metallurgy and Materials, University of Science and Technology Beijing, 30 Xueyuan Road, 100083 Beijing, China b Museum of the Terra-cotta Warriors and Horses of Qin Shihuang, Lintong District, Xi’an, 710600 Shaanxi, China article info abstract

Article history: Shang-dynasty bronzes recovered in the Hanzhong region, Shaanxi province have been receiving Received 9 December 2008 considerable research interest since the 1950s due to their strong regional characteristics. This paper Received in revised form presents preliminary analytical results of 16 samples taken from 13 Hanzhong bronze objects, which, for 9 April 2009 the first time, have revealed their diversity in chemical composition and casting quality. In particular, the Accepted 16 April 2009 finding that some correspondence probably exists between the types of artefact and their materials has significant implications for identifying regional technical characteristics of the Hanzhong bronzes, as well Keywords: as for exploring the interaction between the metropolitan areas of the Shang Kingdom with the areas Shang bronze technology Hanzhong bronze beyond its southwestern frontiers. Scientific analysis of bronzes Ó 2009 Elsevier Ltd. All rights reserved. Regional bronze culture

1. Introduction In July 2006, Professor Jessica Rawson of Oxford University and the authors of this paper travelled to Hanzhong to undertake a field Numerous Shang-dynasty bronzes have been recovered in the investigation of the Shang bronzes recovered there. During the Hanzhong region, Shaanxi province (Fig. 1), since the 1950s, investigation, with gracious assistance of local museums in including ritual vessels, weapons, implements and ornaments. Chenggu and Yangxian counties, we obtained 16 samples for These bronzes occur not only in large numbers, but also present laboratory examination taken from 13 bronze artefacts. This paper a rich range of forms and decorations. Some of them are typical of reports the results of the examination of these 16 samples. The the Shang bronzes from the Central Plains of China, while others purpose of this analytical work is to gain a preliminary under- show clear indigenous characteristics (Fig. 2). Since the 1980s, standing of the materials and manufacturing technologies of the considerable research on Hanzhong bronzes has been carried out Hanzhong bronzes. by many scholars, with a focus on their regional origins or associ- ations, dating and local features, as well as their position con- 2. Sampling and analytical methods necting the metropolitan area of the Shang Kingdom with the areas beyond its southwestern frontiers. Two comprehensive mono- Samples were taken only from objects with damages, casting graphs (Cao, 2006; Zhao, 2006) detail previous research on the lines or repairs that were suitable for sampling, not from complete Hanzhong bronzes. However, little scientific analysis has so far objects in a good state of preservation. For some repaired objects, been undertaken on these bronzes. To our knowledge, the only two samples were taken, one from the object itself and one from published scientific analysis of them is the work carried out by Jin the repair. Attention was paid to taking very small samples Zhengyao and his collaborators, which, for the first time, provides (c. 10 mm3) in order to minimize any damage to the objects. The 13 us with a set of measurements of lead isotope ratios of 31 Hanzhong bronzes, from which the 16 samples were taken, are in the collec- bronzes. Jin’s paper, however, does not present any analytical data tions of two local county museums in Chenggu and Yangxian. These concerning their chemical composition or manufacturing technol- objects include ten vessels (bu, zun, ding and li) and three imple- ogies (Jin et al., 2006). Therefore, to date, their technical charac- ments (two sickle-shaped objects and one yang disc). Information teristics remain poorly understood. about their identification and origins is provided in Table 1. The samples were mounted, ground and polished according to standard metallographic procedures. The polished sections of the * Corresponding author. Tel.: þ86 1062334901; þ86 1062334901. samples were etched with a FeCl3 þ HCl þ alcohol ferric solution E-mail address: [email protected] (K. Chen). (3% FeCl3) to reveal their microstructures. They were examined and

Please cite this article in press as: Mei, J., et al., Scientiﬁc examination of Shang-dynasty bronzes from Hanzhong, Shaanxi Province, China, J. Archaeol. Sci. (2009), doi:10.1016/j.jas.2009.04.017 ARTICLE IN PRESS

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Fig. 1. Map showing the position of the Hanzhong region as well as the sites yielding Shang-dynasty bronzes. photographed with both an optical microscope and a scanning taken as a general indication of the overall composition of the electron microscope (SEM). The aim of metallographic examination samples, due to their small sizes and possible heterogeneity in the was to reveal the microstructures of the samples, providing direct object’s composition. insight into the techniques employed in their manufacture. Elemental analysis was conducted on the polished and un-etched 3. Analysis results sections in the SEM by using an energy-dispersive spectrometer (EDS) for quantitative analysis. This analysis provides essential 3.1. Metallographic examination micro-compositional information, which is vital in understanding the metallurgical processes involved. It should be noted that while The 16 samples were examined and photographed with two the EDS gives an accurate measurement of the composition of the types of optical microscope, namely Jiangnan XJP-100 and Leica small area analyzed in the SEM, this measurement can only be DM4000 M. The examination results are summarized in Table 2.

Fig. 2. Drawings of some bronze objects recovered in Hanzhong (after Cao, 2006 and Zhao, 2006; in different scales, see Table 1 for more information). 1, 4: ding vessels; 2: li vessel; 3: yan vessel; 5–7: zun vessels; 8, 9: bu vessels; 10: yang disk; 11, 12: sickle-shaped objects.

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Table 1 Information concerning bronze samples from Yangxian and Chenggu County museums.a

Objects Origins Original nos. Lab. nos. Sampling point Size (cm) Figures Page nos. bu vessel Anjiacun, Machang, Yangxian AON2 HZ001 casting line, bottom height Fig. 1: 8 152 23.8 bu vessel Anjiacun, Machang, Yangxian AON5 HZ002 broken part height Fig. 1: 9 155 20.5 zun vessel Liulingdu, Xiecun, Yangxian AON10 HZ003 broken part height Fig. 1: 7 062 20.5 ding vessel Longtoucun, Longtou, Chenggu Cu 295 (T699: 1) HZ004 rim height Fig. 1: 1 017 42.3 sickle-shaped object Longtoucun, Longtou, Chenggu Cu 74-5 (T337) HZ005 casting line height Fig. 1: 11 170 43.3 li vessel Longtoucun, Longtou, Chenggu Cu 294 (T698) HZ006 casting line, leg height Fig. 1: 2 028 HZ007 upper part, broken 48 sickle-shaped object Longtoucun, Longtou, Chenggu Cu 281-6 (T356) HZ008 casting line height Fig. 1: 12 176 22 zun vessel (broken) Sucun, Baoshan, Chenggu Cu 18-1 (CH27) HZ009 broken part, foot height Fig. 1: 5 052 HZ010 broken part, foot 43.5 zun vessel Sucun, Baoshan, Chenggu Cu 18-5 (CH18:5) HZ012 repair, foot height Fig. 1: 6 060 HZ013 upper part, broken 35.9 yang disc Sucun, Baoshan, Chenggu Cu 37 (?) HZ014 middle part, broken diameter Fig. 1: 10 (T66) 11.7 yan vessel Longtoucun, Longtou, Chenggu Cu 296 (T700) HZ015 broken part height Fig. 1: 3 038 28.2 guan vessel Wulangcun, Wulang, Chenggu Cu 55 HZ016 middle part, broken height 611 22.2 ding vessel Wulang, Chenggu Cu 22-5 (63) HZ018 casting line, leg height Fig. 1: 4 024 35.2

a Notes: The information given in Table 1, including page nos., comes from Cao (2006). It should be noted that some of this information is different from that given in Zhao (2006).

According to these examination results, the microstructure of inclusions and other phases, the same approach is adopted, taking the 16 samples can be generally divided into three categories: as- multiple measurements on several different regions or particles. In cast bronze, as-cast bronze with heat treatment, and copper. As- the present research, a JEOL JSM-6480 SEM with Noran System6 cast bronzes account for the largest proportion with nine out of the EDS of American Thermo was employed to perform the examina- 16 samples. They show an a solid solution matrix of clear dendritic tion, the accelerating voltage being 20.0 kV and acquisition time segregation, with differing amounts of (a þ d) phases, which reﬂect over 50 s. Tables 3 and 4 give the results of the compositional the different tin content of the samples. Four samples have analysis of these 16 samples as well as their inclusions. It should be a microstructure of cast bronze with heat treatment: the casting noted that in Table 3, the material characterisation follows segregation disappeared in the whole or part of each sample, while a terminology that has been adopted widely among scholars: tin the matrix mainly consists of incompletely homogenized a solid bronze refers to a copper-based alloy containing 2% tin or over, solution and the remaining (a þ d) phases. Slip lines have been a Cu–Sn–Pb ternary alloy contains both tin and lead at the level of observed in the microstructure of the bu vessel (HZ002), which 2% or more; where the tin and lead contents are both less than 2%, suggests the objects have been hot-worked. The remaining three the material concerned is regarded as ‘impure’ copper. samples, two sickle-shaped objects (HZ005 and HZ008) and one The results given in Table 3 are the ﬁrst published group of ding vessel (HZ018) have a microstructure of a copper þ (a þ Cu2O) compositional data for Hanzhong bronzes. Although the results are eutectic. The microstructure of the sickle-shaped object (HZ005) rather limited in terms of sample number, they still provide us with shows that Cu2O aggregated into large particles at the boundaries some remarkable information. Among the 13 objects under of a-Cu, indicating annealed copper. Lead phases exist in nine out of discussion, except for the guan vessel (HZ016), which most likely the 16 samples, mostly present as discrete particles; and some dates to a later period (Cao, 2006, p. 611), the remaining twelve can samples have a high lead content, reaching 30–40 wt%. Further- all be dated to the Shang dynasty. Their compositional character- more, blue–grey inclusions are visible in most of the samples in the istics may be summarized as follows: form of small particles or granules, some co-existing with lead or (a þ d) phases. (1) They are made of three materials: namely Cu–Sn–Pb ternary alloy (six items), tin bronze (Cu–Sn) (three items) and copper 3.2. Chemical composition analysis (three items). (2) Among these twelve objects, nine are vessels and three are The compositional analysis of the 16 samples was carried out in weapons (ornaments?) or ceremonial objects, namely a yang a scanning electron microscope (SEM) by using an energy-disper- disc with central hole (HZ014) and two sickle-shaped objects sive spectrometer (EDS). In principle, the EDS analysis can only (HZ005 and HZ008). It is notable that the two sickle-shaped offer micro-compositional information, which may show some objects are both made of copper, while the yang disc with difference from the actual composition of the sample. In order to central hole, the only weapon-related object under examina- obtain more representative data, several measurements were tion, is made of Cu–Sn bronze with a tin content of nearly 18%, normally taken in different regions of the sample, and the mean the highest among all the samples analyzed. Six of the nine value of these measurements can then be taken as the overall vessels are made of Cu–Sn–Pb ternary alloys, including three composition of the sample. To analyse the composition of the zun with animal face or bird patterns, one bu with dragon

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Table 2 Metallographic examination of the Hanzhong samples.

Lab. nos. Objects Microstructure Technology Figs. HZ001 bu vessel The matrix is a solid solution with indistinct dendritic segregation. Some (a þ d) phases are corroded, cast 3 with a phase being corroded ﬁrst.

HZ002 bu vessel The matrix is re-crystallized a solid solution. Many (a þ d) phases are visible and a large number of lead cast, then heat phases (particles) are scattered evenly. Slip-bands exist in some grains. treatment

HZ003 zun vessel The matrix is a solid solution with dendritic segregation, with a few equiaxial grains observed in limited parts. cast, then heat 4 Many (a þ d) phases are visible. Lead phases are distributed unevenly in dendrites and particles. treatment

HZ004 ding vessel The sample is almost completely corroded. The microstructure of the corrosion products shows the remains cast of segregation and (a þ d) phases, demonstrating it was originally a cast structure.

HZ005 sickle-shaped object The microstructure consists of a solid solution equiaxial grains and (Cu þ Cu2O) eutectic structure. cast 5

HZ006 li vessel The matrix is a solid solution interdendritic segregation associated with some ﬁne (a þ d) phases. Equiaxial cast and 6 and twinned grains are observed in some areas. hot-worked HZ007 The matrix is a solid solution with some segregation and a small amount of (a þ d) phases visible. Many lead cast, then heat 7 particles are distributed evenly across the matrix. treatment

HZ008 sickle-shaped object The matrix has a typical (Cu þ Cu2O) eutectic structure. A few small blue–grey inclusions as well as casting cast 8 porosity are visible.

HZ009 zun vessel The microstructure consists of a solid solution with clear interdendritic segregation. A small amount of (a þ d) cast phases is visible. Many lead particles are distributed unevenly. HZ010 The matrix is a solid solution with interdendritic segregation. A small amount of (a þ d) phases and many cast 9 lead particles are visible.

HZ012 zun vessel The matrix shows a solid solution of clearly dendritic segregation in a ﬁne microstructure. A small quantity cast 10 of (a þ d) phase is visible. HZ013 The matrix shows a clear dendritic segregation of a solid solution. A small quantity of (a þ d) phase is visible. cast There are also particles, some in a ‘dendritic’ form. Many inclusions are present as blue–grey particles.

HZ014 yang disc The microstructure is a solid solution with some segregation. A large number of (a þ d) phase is visible, cast 11 in which d phase predominates.

HZ015 yan vessel The matrix is a solid solution with obvious dendritic segregation. Many small lead particles are scattered cast evenly across the matrix.

HZ016 guan vessel The matrix is a solid solution with clear dendritic segregation. A small number of (a þ d) phase is visible. cast Lead occurs as round or dendritic inclusions, which are mostly corroded and scattered unevenly.

HZ018 ding vessel The matrix shows a hypoeutectic microstructure of Cuþ(Cu þ Cu2O). The eutectic phases exist along cast 12 the grain boundaries, some of them are corroded.

patterns, one li and one yan; two vessels (bu and ding) are Cu– typically copper oxide, which is in stark contrast to those identified Sn bronze. The only vessel made of copper is the ding with in the bronze objects. a line pattern, which deserves further investigation. (3) The tin content of the Cu–Sn bronze objects ranges from 4% to 18%; Cu–Sn–Pb ternary alloys have tin content of between 3.7% 4. Discussion and 12.4%, while their lead content, except for one of 6.3%, is 20 % or more, the highest even reaching 38%. 4.1. The relation between artefact categories and materials (4) Two vessels (li and zun) were sampled from both the vessel body and re-cast or repaired parts respectively. Analysis of the This preliminary analysis of Hanzhong bronzes suggests that four samples from these two vessels reveals two different some correspondence probably exists between the types of artefact circumstances: for the li vessel, its body (HZ007) is made of Cu– and their materials. The two sickle-shaped artefacts, which exhibit Sn–Pb alloy, differing from the patching material on its leg a strong local flavour, are both made of copper; the yang disc with (HZ006), which is of Cu–Sn bronze. In the case of the zun vessel, central hole that also shows such local characteristic is made of Cu– its body and the repaired part on its base are both made of Cu– Sn bronze with a very high tin content (18%). Six of nine vessels Sn–Pb alloys, which, however, show a significant difference in examined are made of Cu–Sn–Pb ternary alloys with relatively high their lead content, with the body (HZ013) reaching as high as lead contents, while the other three include two vessels of Cu–Sn 38% and the repaired part (HZ012), containing only 6.3%. and one vessel of copper. Further analysis should be undertaken to test whether such an apparent correspondence is purely accidental The presence of blue–grey inclusions in most of the samples has or occurs regularly. already been noted in the above metallographic examination. Table According to Zhao Congcang’s summary, among the more than 4 shows that most of these inclusions are copper sulphide with 700 Shang bronzes recovered in the Hanzhong region, there are 79 a weight ratio of 4:1 between copper and sulphur, suggesting their sickle-shaped objects, the fourth largest group among all cate- chemical formula is Cu2S (cuprous sulphide). Inclusions of slightly gories, after yang discs with pyramid projection (193), yang discs different chemical compositions exist in three samples, and they with central hole (90) and the triangular ge with straight handle are copper sulphide containing some iron at a level of 1.8–14.1%. In (85) (Zhao, 2006, p. 218, Table 5). Many of the sickle-shaped objects the sickle-shaped objects made of copper, the inclusions are are of rather poor casting quality with many porosities, mostly

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Fig. 3. As-cast dendritic microstructure of the bu (HZ001) with considerable (a þ d) Fig. 5. Copper annealing microstructure of the sickle-shaped object (HZ005). Cu O and phases present. The black phases are mostly corrosion products, see also Fig. 13. 2 sulphide inclusions assemble at the grain boundaries, see also Fig. 14. caused by the absorption of oxygen (referred to as ‘‘copper leaking’’ of Cu–Sn–Pb ternary alloys with relatively high lead content, by Zhao Congcang) (Zhao, 2006, pp. 16–26), as illustrated in Cao a feature deserving special attention. These six vessels include (2006) by the pictures of Cu 74-3 (p. 168), Cu 74-5 (p. 170), Cu 281-5 three zun,abu,ali and a yan. The three zun contain tin at a level of (p. 175), Cu 281-6 (p. 176) and Cu 69-3 (p. 180), etc. Compared to 3–9%, but lead at an unusually high level of 27–38%. Lead content bronze, copper is more apt to give rise to defects because of its has a strong impact on the cast-ability of Cu–Sn–Pb ternary alloys. higher melting point and the absorption of oxygen during casting In general, the addition of lead leads to significant improvements in procedure. Therefore, it is reasonable to suppose that these coarse the fluidity and mould-filling capability of Cu–Sn bronze. Experi- and porous sickle-shaped objects were probably all made of copper. ments show that the fluidity of bronze reaches a peak when the Further analytical work is ongoing to validate this supposition lead content is about 10–15%, but declines sharply when lead is (Chen et al., 2009). more than 15%; mould-filling capability will initially be improved As we can see from dozens of published photographs in Cao when lead is added to the bronze, but will decline when lead (2006, pp. 407–510), most of the yang discs, no matter whether content is more than 15% and reaches 20% (Wu and Li, 1988). The they are with central hole or pyramid projection, exhibit good three zun vessels, especially the zun with animal face patterns (Cu casting quality without obvious defects. Although it is difficult to 18-5, HZ013), are crudely cast with illegible external patterns. Their say whether all of the yang discs are made of tin bronze, like the low quality is obviously due to the reduced casting capability sample HZ014, the high level of their casting quality is in sharp caused by the high lead content (38%). By contrast, the bu vessel contrast to that of the sickle-shaped objects. Further examination made of tin bronze, containing 16% Sn (AON2, HZ001), exhibits should help clarify whether tin bronze is the main material for a high level of casting quality, as demonstrated by its fine patterns fabricating the yang discs. of decoration, white shiny texture and well preserved condition. The composition of vessels is obviously more complicated. As Obviously, the material used was of much better quality. Similar to mentioned earlier, among the nine vessels analyzed, six are made the two sickle-shaped objects, the ding vessel made of copper

Fig. 4. Microstructure of partly annealed casting bronze of the zun (HZ003) with the Fig. 6. Fine dendrite segregation of the patched part of the li (HZ006). Deformation of remaining (a þ d) phases and inclusion particles on grain boundaries. The black phases some grains can be observed, indicating that the hot-working process was applied are lead particles, see also Fig. 17. below the re-crystallization temperature.

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Fig. 7. Incompletely homogenized microstructure of the sample from the body of the li Fig. 9. Microstructure of a solid solution of the sample from the body of the zun (HZ007). Cast segregation and the remaining (a þ d) phases are still visible. (HZ010). This view shows clear dendritic segregation of the matrix with a few (a þ d) phases. (Cu 22-5, HZ018) is also of poor casting quality, with many small holes on the surface, due to the absorption of oxygen and filling others were rather poorly executed, leading to not only illegible defects during the casting process. surface patterns, but also ubiquitous casting defects as well as the The co-existence of various materials among the Hanzhong subsequent necessity for repairs. Such diversity in manufacturing Shang bronzes implies that they probably came from several techniques reflects the complexity of provenance and date. They different production centres, or were made at different workshops. must have come from various sources, some were produced locally, This is undoubtedly an important issue that should be explored in others transported into Hangzhong from other regions, while they detail through further scientific and stylistic analysis of more span from the early Shang period (the lower Erligang culture) to the Hanzhong bronzes. late Shang period (the phase IV of Yinxu culture). Second, most of the functional weapons, such as ge, mao and 4.2. Technological characteristics of Hanzhong Shang bronzes yue, are of good casting quality with few defects. However, the sickle-shaped objects, which may have been used in ceremonial With regard to the technological characteristics of the Hanz- activities, are often of poor quality. Whether such a quality differ- hong bronzes, the first noticeable phenomenon is that these objects ence indicates an intentional selection of materials and technolo- are clearly not all of the same manufacturing quality. For instance, gies or just reflects the various origins of the objects is at present the casting quality of the vessels exhibits a wide range of difference, unknown. Further research needs to be conducted in order to although they were all produced using the technique of piece- answer this question. mould casting. Some vessels are finely cast, with excellent texture Third, it is notable that many objects, including vessels, masks and vivid patterns, demonstrating a high level of manufacturing and sickle-shaped objects show signs of re-casting. Such work was skill comparable to the high-quality bronze vessels found in the carried out on the legs of the li (Cu 294, HZ007) and yan (Cu 296, metropolitan region of the Shang Kingdom. By contrast, some HZ015) vessels, both of which are three-legged containers. Casting

Fig. 8. Cu þ Cu2O eutectic microstructure of the sickle-shaped object (HZ008). The Fig. 10. Fine dendrite segregation microstructure of the sample from the base of the black holes are contraction cavities, see also Fig. 15. zun (HZ012). A small quantity of (a þ d) phases are present between the dendrites.

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The last feature is the production of the small holes on the yang discs. It is obvious that these were made by grinding through the objects rather than by casting out. Clear traces of the use of grinding are illustrated by the yang disc numbered Cu 57-119 (Cao, 2006, pp. 449–450). It is worth considering why the Hanzhong people used such a time-consuming and laborious technique rather than casting the holes directly in objects. Was there any relationship between the grinding techniques and the use of the yang discs?

4.3. A preliminary technological comparison with bronzes from other Shang period sites

From the above preliminary analysis, we can note that the Hanzhong bronzes exhibit two remarkable technological charac- ters. First, the vessels are mostly made of Cu–Sn–Pb ternary alloy, and their lead content is generally higher than 20%; Second, some items, especially the sickle-shaped objects, possibly used for ceremonial or religious activities, were made of copper. According to typological analysis, the dates of the Hanzhong bronzes embrace Fig. 11. As-cast microstructure of the yang disc with central hole (HZ014). The matrix is a long period, ranging from the Lower Erligang Culture (early Shang pure and many high tin phases are observed to be d phases. period, about 15th century BC) to the Yinxu Culture (Phase IV, late Shang period, about 12th century BC). Therefore, it is reasonable to seams and traces of overflowed metal are visible on the re-cast compare the analytic results of the Hanzhong bronzes with the parts of the two vessels, suggesting the employment of a rough re- bronzes from other Shang period sites, such as Panlongcheng in cast/cast-joint technology that involved fixing the clay mould on Hubei Province, Yinxu in Anyang city, Henan Province, Dayangzhou the legs first and then pouring the liquid metal directly into the in Xin’gan, Jiangxi Province and the pre-Zhou sites in the Guanz- mould. Another example is a small piece of re-casting on the hong region, Shaanxi Province, etc. shoulder of the bu (AON2, HZ002) vessel. There is no liquid metal Hao Xin and Sun Shuyun analyzed 27 vessels, four weapons and overflow around the re-cast location, and the decoration pattern on one implement object unearthed from the Panlongcheng site in the re-cast piece fits very well to the patterns on the main body of Hubei Province. They found that all the samples were Cu–Sn–Pb the vessel, displaying excellent skill (Zhao, 2006, plate 43). It may ternary alloy, except for a vessel sample of Cu–Sn bronze. No copper be inferred that the casting of the main body and the re-cast section objects were found. 15 samples, all from vessels, had a lead content was probably undertaken at the same workshop. The re-casting above 20%, up to 31%. They compared Panlongcheng bronzes with process may have been carried out just after the main body was those from the Erligang site in Zhengzhou and other early Shang produced. By contrast, it is difficult to judge when the re-casting sites, and pointed out differences and similarities between these work on the li (Cu 294, HZ007) and yan (Cu 296, HZ105) vessels was two groups. The major difference is that Panlongcheng has more carried out, especially as compositional analysis has revealed high-lead-content (Pb > 10%) bronzes than Erligang and other early obvious differences in their materials: the main body of the li vessel Shang sites, while the similarities are: (1) No copper objects were is Cu–Sn–Pb ternary alloy, while the patch on the leg is Cu–Sn found in either group. (2) Cu–Sn–Pb ternary alloys are more bronze. Similarly, for the zun (Cu 18-5) vessel, the lead content of common than Cu–Sn bronzes, suggesting that the use of Cu–Sn–Pb the main body is different from the re-cast patch, although they are ternary alloys for casting objects was the predominant technique. both Cu–Sn–Pb ternary alloys. (3) The tin content in the tools and weapons is higher than that in the vessels and ritual objects, while the lead content is lower. Moreover, they noted a compositional difference between the bronzes from Panlongcheng and Yinxu, the latter, which came from both large royal cemeteries and small tombs, having lower lead content. Cu–Sn bronze was found to be the predominant alloy in the objects from large royal cemeteries. They believe that the compositional differences may have been related to a shortage of tin at that time. As capital sites, Erligang and Yinxu both had a preferential access to the supply of tin by comparison with Pan- longcheng, a regional city (Hao and Sun, 2001). Li Minsheng et al. analyzed more than 100 bronze objects excavated from the royal tomb of Fu Hao (concubine of the Shang king, Wu Ding) and from the commoners’ tombs in the western part of the Yinxu site. They discovered that among the bronzes from Fu Hao’s tomb, the major alloy type was Cu–Sn bronze (73% of the analyzed objects), the remaining being Cu–Sn–Pb ternary alloy. By contrast, the objects from commoners’ tombs were mainly made of lead–copper binary alloy (44%), then Cu–Sn–Pb ternary alloy (26%), with only four copper items identified (9% of the examined objects). The researchers suggested that because of the production of numerous high tin bronzes, copper and tin became scarce and Fig. 12. Hypoeutectic microstructure of copper of the ding (HZ018). The eutectics of

Cu þ Cu2O exist at the grain boundaries, and the dark areas are porosity formed by the expensive from phase III of the Yinxu culture onwards, which corrosion of the eutectic. promoted the smelting and use of lead. This seems to be

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Table 3 Results of bulk compositional analysis of the Hanzhong samples.a

Objects Lab Nos. Composition (wt %) Notes Material (Figures)

Cu Sn Pb bu vessel HZ001 84.2 15.8 – micro-area Cu–Sn (Fig. 13) 83.2 16.8 – micro-area 83.7 16.3 – average bu vessel HZ002 59.6 13.3 27.2 micro-area Cu–Sn–Pb 67.3 11.5 21.2 micro-area 63.4 12.4 24.2 average zun vessel HZ003 57.9 9.0 33.1 full area acquisition Cu–Sn–Pb ding vessel HZ004 91.5 8.5 – micro-area Cu–Sn 89.5 10.5 – micro-area 93.6 6.4 – micro-area 91.5 8.5 – average sickle-shaped object HZ005 100 – – micro-area Cu (Fig. 14) 100 – – micro-area 100 – – average li vessel HZ006 96.4 3.6 – micro-area Cu–Sn 95.8 4.2 – micro-area 95.4 4.7 – micro-area 95.9 4.1 – average HZ007 72.0 8.1 19.9 micro-area Cu–Sn–Pb 68.3 7.8 23.9 micro-area 70.2 8.0 21.9 average sickle-shaped object HZ008 100 – – micro-area Cu (Fig. 15) 100 – – micro-area 100 – – average zun vessel (damaged) HZ009 68.4 8.0 23.5 micro-area Cu–Sn–Pb 64.5 8.2 27.4 micro-area 66.5 8.1 25.4 average HZ010 64.2 7.9 27.9 full area acquisition Cu–Sn–Pb zun vessel HZ012 86.3 7.4 6.3 full area acquisition Cu–Sn–Pb HZ013 58.1 3.7 38.2 full area acquisition Cu–Sn–Pb (Fig. 16) yang disc HZ014 81.8 18.2 – micro-area Cu–Sn 82.5 17.5 – micro-area 82.2 17.8 – average yan vessel HZ015 72.1 8.9 19.1 full area acquisition Cu–Sn–Pb guan vessel HZ016 77.1 6.9 16.0 micro-area Cu–Sn–Pb 79.1 7.4 13.6 micro-area 78.1 7.1 14.8 average ding vessel HZ018 100 – – micro-area Cu 100 – – micro-area 100 – – average

a Note: In this and the following tables, the overall compositional data have been normalized to 100 wt%. Most of the samples were examined at two or three different micro- areas (about 1 w 3mm2) in order to minimize the measurement errors. The average composition is the mean value of different micro-area compositions. ‘‘–’’ stands for ‘‘undetected’’.

demonstrated not only by the increase in leaded copper vessels Table 4 over time, but also by the emergence of lead weapons (Laboratory Results of compositional analysis of the inclusions in some Hanzhong samples. of the Institute of Archaeology, 1982; Li et al., 1984). Zhao Chunyan carried out compositional analysis of about 200 Objects Lab Nos. Inclusions (wt %) Figures bronze items excavated from the Yinxu site. She found that, from Cu S Fe Others phase I to phase IV of the Yinxu culture, the tin content in the bu vessel HZ002 76.1 22.1 1.8 vessels declined significantly, while the lead content increased. Of zun vessel HZ003 65.8 23.0 11.3 Fig. 17 eight objects dating to phase I, one is copper, one Cu–Sn bronze, sickle-shaped object HZ005 92.5 7.6 – Fig. 14 li vessel HZ006 83.5 16.6 – one lead–copper alloy and five Cu–Sn–Pb ternary alloy (three HZ007 77.9 22.1 – vessels and two ge knifes). All contain less than 6% lead, except for sickle-shaped object HZ008 45.7 – 37.0 O-17.3 Fig. 15 one item that reached nearly 20%. The phase II objects are mainly zun vessel (damaged) HZ009 77.0 23.0 – made of Cu–Sn bronzes, with a relatively high tin content. Cu–Sn– HZ010 77.3 20.6 – Sn-2.1 zun vessel HZ012 76.7 23.3 – Pb ternary alloy items are next in number, all with lead content HZ013 79.9 20.2 – Fig. 16 lower than 15%. Only two items were identified as copper. The yang disc HZ014 68.4 8.0 14.1 Sn-9.6 phase III bronzes are characterized by the predominance of Cu–Sn– yan vessel HZ015 77.7 22.3 – Fig. 18 Pb ternary alloys, and some items contained a rather higher lead guan vessel HZ016 78.1 21.9 – content, up to about 26%. Weapons of a lead–copper binary alloy

J. Mei et al. / Journal of Archaeological Science xxx (2009) 1–11 9

Fig. 13. BSE image of the bu (HZ001). No lead is detected in the matrix, and the dark Fig. 15. BSE image of the copper eutectic microstructure (HZ008). Some relatively big phases are mostly corrosion production. particles of Cu2O have been found at the grain boundaries. occurred in large quantities, with some containing lead as high as five Cu–Sn bronze, three lead–copper binary alloys and 14 Cu–Sn– 40%. Only two copper vessels were identified. Cu–Sn–Pb ternary Pb ternary alloys. The four copper items include two ding vessels alloys are also the main material in the phase IV bronzes, though unearthed from Nianzipo in Changwu County, which can be dated the number of lead–copper binary vessels increased markedly. to phase II of the Yinxu culture. The two ding vessels are cast Some vessels contain quite high lead content, the highest up to roughly with the presence of many shrinkage cavities. There are about 29%. One copper and two lead containers were also identi- four ritual vessels, seven weapons and three ornaments of Cu–Sn– fied. Among about 200 analyzed samples, including weapons and Pb ternary alloy, all of which have lead content lower than 20%, vessels, only six copper items have been found, mostly vessels except for one gui vessel that reached 32.4%. Three items were (Zhao, 2004). made of lead–copper binary alloy, one ding vessel from Zhengjiapo Pieter Meyers et al. (1987) examined 104 samples from 99 Shang in Wugong County contains only 2.7% lead; one ge knife from bronze vessels, showing that most of them are Cu–Sn–Pb ternary a Zhou people’s cemetery in Beilu¨ in Fufeng County had lead as high alloy, while a few are Cu–Sn bronze and none are copper. Twelve as 28.6%, and another ge knife from the Hejiacun site in Qishan samples contain a lead content higher than 20%, the highest being County contained 4.2% lead (Yang, 2002). 32%. Fan and Su (1997) analyzed 18 samples from Xin’gan Shang According to typological comparison, the Hanzhong bronzes cemetery in Jiangxi Province using quantitative chemical methods. show close relationships not only with Shang culture of the China’s They discovered that the Xin’gan objects mostly consist of Cu–Sn– Central Plains across whole of the Shang period, but also with Pb ternary alloy, with a tin content of up to 20% and a lead content bronze cultures in western Sichuan and in the middle and lower under 10%. Again, no copper items were found. parts of the Yangzi River valley, as well as the pre-Zhou and Shang Yang Junchang analyzed the composition of 26 pre-Zhou items cultures in the Guanzhong area (Shaanxi province) (Zhao, 2006). from Guanzhong area of Shaanxi Province, revealing four copper, On the other hand, the Hanzhong bronzes demonstrate significant

Fig. 14. BSE image of the sickle-shaped object (HZ005). Cu2O is concentrated at the Fig. 16. BSE image of the sample the upper body of the zun (HZ013). Many bright white grain boundaries and forms numerous dark particles. lead particles and some co-existing sulphide inclusion granules in black are visible.

10 J. Mei et al. / Journal of Archaeological Science xxx (2009) 1–11

copper. As has been mentioned above, well-known Shang sites such as Erligang, Panglongcheng and Xin’gan have not yielded any copper items. At Yinxu, phase I produced one copper item, phases II and III two items and phase IV one. Xin’gan has not yielded any. However, the pre-Zhou sites in the Guanzhong region seem to have a higher rate. Here, four copper objects have been identified among 26 items, in particular the two copper ding vessels unearthed from Nianzipo in Changwu County, which seem to echo the copper ding from Hanzhong. It is worth mentioning that one copper ding was unearthed at a Shang cemetery in the Jingjie village, Lingshi County, Shanxi Province, which, just like the Hanzhong piece, belonged to the peripheral regions of Shang culture. These two copper ding vessels are similar to each other in size and shape (Chen and Mei, 2006). Another notable point is that the high lead content of the Hanzhong bronzes seems to be more comparable with the bronzes from Panlongcheng and Yinxu phases III and IV than those from Erligang, Xin’gan, Yinxu phases I and II, Jingjie and pre-Zhou sites in the Guanzhong region. Certainly, this is only a preliminary inter- Fig. 17. BSE image of the zun (HZ003). Many bright white lead particles are present, pretation and further analytical data are needed to support or while the sulphide inclusions are dark particles or bands, most of them co-existing with lead. supplement it. The high lead content is a notable technological characteristic of many Hanzhong bronzes, and the preliminary local character as well, as exemplified by the sickle-shaped objects, recognition of this characteristic is of significance for the under- zhang-shaped objects and numerous yang discs with central hole or standing of the relationship between the central Shang area and its pyramid projection. periphery, especially concerning contacts between the Shang With regard to alloy composition, the Hanzhong bronzes show culture in the Central Plains and the Sanxingdui culture in Sichuan. some difference as well as similarities to Shang bronzes from other regions. The major similarity is attested by the adoption of Cu–Sn– 5. Conclusions Pb ternary alloy as the predominant material in many Shang sites, such as Panlongcheng, Yinxu (phase III and phase IV) and Xin’gan. From the above analysis and discussion, the major results can be The differences are best demonstrated by the high proportion of summarized as follows: copper items among the Hanzhong bronzes. Three copper objects have been identified among the 13 items examined, including two 1. The twelve Shang bronzes include six Cu–Sn–Pb ternary alloy, sickle-shaped objects and one ding vessel. The two sickle-shaped three Cu–Sn bronze and three copper objects. The lead content objects display a marked local flavour, while the poor casting of the Cu–Sn–Pb is generally higher than 20%. Copper was quality of the ding vessel seems to suggest that it may have been employed to cast one ding vessel and two ceremonial sickle- cast locally as an imitation of metropolitan products. Copper has shaped objects. The guan vessel (HZ016), assumed to date to a relative high melting point (1083 C) and poor fluidity. It is prone the Han Dynasty, is made of Cu–Sn–Pb ternary alloy. to absorb oxygen during the casting process, and thus to form 2. The high lead content seems to be a notable technological numerous shrinkage cavities of varying sizes during cooling. characteristic of many Hanzhong bronze vessels, suggesting Therefore, copper would not normally be used to cast artefacts, that the Hanzhong bronzes are more comparable with the especially vessels. As far as the analytical data available to date is bronzes from Panlongcheng and Yinxu phases III and IV than concerned, few ding vessel or other containers were cast from with those from Erligang, Xin’gan, Yinxu phases I and II, Jingjie and pre-Zhou sites in the Guanzhong region. Further analysis is needed to confirm this preliminary observation. 3. The Hanzhong bronzes display a diversity of casting quality, which may have resulted from the variations in their sources of material and manufacturing workshops.

The results presented in this paper are obviously preliminary, as the types and numbers of objects under examination are still very limited. They, however, mark a good start to the technical study of the Hanzhong bronzes. Considering their strong local or regional characteristics as well as Hanzhong’s geographic position in linking the Central plains to southwest China, further analytical research will be of signiﬁcance to the exploration of the interaction between the Shang Kingdom and its peripheral regions, especially the remote areas in the southwest, and thereby to advancing our understanding of Shang civilization.

Acknowledgements

The authors would like to thank the Shaanxi Institute of Fig. 18. BSE image of the yan vessel (HZ015). Many bright white lead phases, some Archaeology, the Chenggu County Museum, the Yangxian County associated with dark particles of inclusions. Museum and the Hanzhong City Museum for their kind support of

J. Mei et al. / Journal of Archaeological Science xxx (2009) 1–11 11 this research. They are also grateful to Professors Rubin Han and Chen, K., Rehren, Th., Mei, J., Zhao, C., 2009. Special alloys from remote frontiers of Shuyun Sun, Associate Professor Xiuhui Li, of the Institute of the Shang Kingdom: scientific study of the Hanzhong Bronzes from southwestern Shaanxi, China. Journal of Archaeological Science 36. Historical Metallurgy and Materials, University of Science and Fan, X., Su, R., 1997. Composition of the bronzes from Shang Cemetery in Xin’gan. In: Technology Beijing, for their valuable suggestion at the beginning Jiangxi Provincial Institute of Archaeology and Cultural Relics (Ed.), Shang of this research and discussion on the analytical results. Professor Cemetery in Xin’gan. The Cultural Relics Press, Beijing, pp. 241–244 (in Chinese). Thilo Rehren of the UCL Institute of Archaeology deserves our Hao, X., Sun, S., 2001. The analysis and preliminary research on the Shang Dynasty appreciation for his huge help with this research. Grateful thanks Bronze from the Panlongcheng site. In: Hubei Provincial Institute of Archae- are also due to Professor Jessica Rawson of the University of Oxford, ology and Cultural Relics (Ed.), PanlongchengdReport of the Excavation from 1963 to 1994. The Cultural Relics Press, Beijing, pp. 517–538 (in Chiese). Mr. John Moffett of the Needham Research Institute and Dr. Marcos Jin, Z., et al., 2006. Lead isotope analysis of the bronzes from the Baoshan Site and Martinon-Torres of the UCL Institute of Archaeology, for their great Cheng-Yang Bronze group and its relevant issues. In: Zhao, C. (Ed.), The Cheng- help with revising this manuscript. Any errors in this paper are, of Yang Bronze. Science Press, Beijing, pp. 250–259 (in Chinese). Laboratory in the Institute of Archaeology, Chinese Academy of Social Sciences, course, our own. 1982. Report on the compositional analysis of the metal artefacts from Yinxu This research was funded by the Chinese State Administration (I): the bronzes from Fuhao Tomb. Kaoguxue Jikan (Collected Papers on for Cultural Heritage under a Research Programme for Conservation Archaeology) 2, 181–193 (in Chinese). Science and Technology. Some laboratory work was undertaken at Li, M., Huang, S., Ji, L., 1984. Report on the compositional analysis of the metal artefacts from Yinxu (II): the bronzes and lead objects from Western Yinxu Site. the Wolfson Archaeological Science Laboratories at the UCL Insti- Kaoguxue Jikan (Collected Papers on Archaeology) 4, 328–333 (in Chinese). tute of Archaeology, and was funded by the European Union under Meyers, P., Holmes, L.L., Sayre, E.V., 1987. Elemental composition. In: Bagley, R.W. contract MEST-2004-519504 for Marie Curie EST Action Science and (Ed.), Shang Ritual Bronzes in the Arthur M. Sackler Collections. The Arthur M. Sackler Foundation, Washington, pp. 553–557. Conservation in Archaeology (2007) and by the China Scholarship Wu, K. and Li, X., 1988. The impact of lead on the property of bronze drums. pp. 5–7. Council under a State Scholarship Fund (2007–2008). (Unpublished manuscript, in Chinese). Yang, J., 2002. Technological Investigation and Comparative Research on the Pre- References Zhou and Early Zhou Bronzes from the Guanzhong Area in Shaanxi Province. A PhD dissertation presented to the University of Science and Technology Beijing, Cao, W. (Ed.), 2006. Shang Bronze from Hanzhong (I–III). The Sichuan Press Group Beijing. (in Chinese). and the Bashu Press, Chengdu (in Chinese). Zhao, C., 2004. Scientific study on the bronzes unearthed from the Yinxu Site, Chen, K., Mei, J., 2006. Scientific analysis of the bronzes from the Shang cemetery in Anyang. Kaoguxue Jikan (Collected Papers on Archaeology) 15, 243–268 (in Jingjie village, Lingshi county, Shanxi Province. In: Hai, J., Han, B. (Eds.), Shang Chinese). Cemetery in Lingshi Jingjie. The Cultural Relics Press, Beijing, pp. 209–228 (in Zhao, C. (Ed.), 2006. The Cheng-Yang Bronzes. The Science Press, Beijing Chinese). (in Chinese).

Please cite this article in press as: Mei, J., et al., Scientiﬁc examination of Shang-dynasty bronzes from Hanzhong, Shaanxi Province, China, J. Archaeol. Sci. (2009), doi:10.1016/j.jas.2009.04.017