1 Introduction

Bronze vessel casting technology in Shang dynasty China has been a topic of interest for archaeologists throughout history. Their interest and fascination with the bronze vessels include use (Loehr 1953; Reinhardt 2015; Uchida 2013), type (Yue et al. 2008), production (Bagley 1990, 2009; Uchida and Yoshiyuki 2017; Yi 2013), motif (Li 2008; Yue 2003), and social factors (Chang 1983; Franklin 1999). Bronze vessels of the Shang dynasty were a symbol of prestige and power (Chang 1983). These vessels were used for ancestral worship by the elites and symbolized their connection to power and their king (Bagley 1980, 1987; Chang 1980, 1983). While the bronze vessels were the elites’ property, the casting moulds were the artisans’ tools. By focusing our research on the bronze vessel casting moulds, we put the artisans and their knowledge into focus. Thus, bringing new discussion on the Shang society through another societal group not depicted in historical writings.

Bronze vessel casting moulds or also known as piece moulds is a group of artifacts made specifically for casting bronze vessels (Bagley 1990, 1999; Chase 1991). The use of these artifacts for the production of bronze vessels began during the Erlitou period (Bagley 1990) and became the most prominent during the Shang and Zhou dynasties (Bagley 1980, 1999). The piece moulds were foundry ceramics made to produce the bronze vessels by retaining the molten bronze in its cavity to form the vessel’s shape and design as it cools. The artisans produced these moulds in sections and pieced together to form the exterior (in the form of moulds) and interior portion (cores) of the bronze vessel (Bagley 1990; Barnard 1961; Chase 1991).

Bronze vessel casting mould research has gained some interest from their production method (Bagley 2009; Liu 2019; Nickel 2006), production distribution (Li 2007), and raw material (Cheng and Shen 2019; Freestone et al. 1989; Stoltman et al. 2018). These studies on bronze casting moulds incorporate another facet to our comprehension of bronze casting technology. This research will build upon this to add the artisans into the discussion.

Liu (2019) compiled the most comprehensive research on the Anyang site’s bronze casting technology, and this involves the entire production of the casting moulds and the bronze vessels uncovered in the Anyang site. Her research allows for a comprehensive overview of the bronze casting technology at the late Anyang capital. Thus, it lacks the intricacies in analyzing the production sequence from the same moulds. This research will expand on Liu’s (2019) discussion to connect the different production steps separated by mould types to comprehend the artisan’s actions and thought process throughout the production method. Without the correlation between the multiple steps involved, we cannot further discuss and comprehend the artisans as individuals who lived and worked in the Shang dynasty capital of Anyang.

Past researchers tend to focus on one aspect of the casting moulds, such as the raw material and its processing method (Freestone et al. 1989; Stoltman et al. 2009; Zhao et al. 2010), forming method (Bagley 1990; Yue et al. 2012; Zhao and Guo 2009), firing (Jin et al. 2015; Tan 1999), and use (Liu et al. 2009). These are fundamental aspects of our bronze casting mould knowledge and understanding. Still, these studies are fragmentary in understanding the casting moulds as objects involving the interconnection of all of the steps of production, knowledge, and artisans’ organization. By breaking down the casting moulds and analyzing them according to their separate steps, we cannot see the entire picture in which the artisans carried out their craft. There is a direct influence in every step selected in a sequence of production, and often the decision made for one step may limit other steps within the series in material and technological abilities of the artifacts. These decisions ultimately lie in the artisans’ access to the raw material and knowledge.

By looking at the entire production sequence of the Anyang casting moulds, we see the material’s transition from the beginning to the end and how the artisans made the casting moulds. The raw material’s transformation to the final product directly reflects the artisan’s solution to their assigned task. In the bronze casting artisans, their goal was to produce a mould that can form molten bronze, but this research will highlight the steps they took, and the knowledge required to solve their issues in creating the bronze vessel casting moulds. Thus, this article will discuss human involvement with the material and technology by looking at the casting mould’s sequence of production to the Anyang site’s artifacts through the casting moulds housed in the Royal Ontario Museum.

2 Background: Anyang and the bronze foundry sites

Huanbei Shang city, found in the Northeast corner of the general Anyang site, is not part of the analysis in this article. The Anyang site discussed in this research focused on the late Shang city found south of the Huanbei river. Anyang, also known as the Yinxu site (1300 − 1046), is a late Shang dynasty capital located in present Anyang city, Henan Province. This site was where archaeologists discovered the inscribed oracle bones, the late Shang dynasty kings’ burials, and their capital complex. This invaluable find gave us further insight into the people, political structure, and their use of the landscape.

Much current research has focused on the various workshops uncovered during Anyang’s excavations. These workshops include bronze vessel foundries, pottery workshops, bone carving workshops, and jade workshops (He 2019; Li 2007). These workshops expand our understanding of the capital’s spatial management and the types of artisans present in support of the elites and the population to supply the goods they need (Franklin 1999; Li 2007). These workshops show that the capital employed various skilled individuals who produced the artifacts uncovered today.

Five bronze foundry regions (Fig. 1), distributed throughout the Anyang site, produced bronze vessels, chariot hardware, and weapons in various degrees (Li 2007). Bronze was an essential commodity to the elites of Anyang, and this is evident with the locations of these foundry sites. Despite the importance of bronze objects, all foundry sites were beyond the temple/palace complex except the Xiaotun foundry region (Fig. 1). The degree of spatial specialization in production is material-based, with bronze casting as the workshops’ sole purpose (Li 2007). However, the foundries lack further differentiation in the bronze artifact types made in the foundries or variations in the step of production (Li 2007).

Fig. 1
figure 1

Anyang (Yinxu) site boundary (map after Stotman et al. 2008), with the five foundry regions circled in blue and specific foundry sites indicated by orange circles (Li 2007; Anyang Municipal Institute of Cultural Relics and Archaeology 2018)

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3 Theoretic considerations on sequence of production

Andre Leroi-Gorham first developed the sequence of production to analyze artisan’s choices in producing the artifacts (Dobres 2010; Killick 2004; Leroi-Gourhan 1964; André Leroi-Gourhan 1964). This theory observes the transitions of the raw material to the final product to determine technological and thoughts of production of the artisans through the artifact’s life cycle (Lemonnier 1986; Schlanger 2005). By using this theory, we can link the artisan’s interaction spheres to the artifacts.

This research defines the bronze vessel mould artisans as those who produced and used the casting moulds. Thus, this article will focus on the choices and steps made by a group of artisans who produced the casting moulds using the same methods and were involved in the casting moulds’ final product. Influences in the production may result from the elite consumer’s preferences and the artisans’ specializations, but this is beyond the scope of this research. Here, the organization is defined by how the artisans separated the various steps to produce the artifacts observable today.

The choices made by the artisans fall into five specific levels: raw materials, tools, energy source, techniques, and the sequence (Sillar and Tite 2000). All of these are linked within the production to produce the intended artifact. The raw material selected by the artisan must meet the requirements of the other levels. If the artisans lack sufficient tools, energy, techniques, or the sequence, the production will fail. The silt-rich material selected by the artisans (Freestone et al. 1989; Liu et al. 2008; Stoltman et al. 2009) must match the bronze alloys (Uchida and Yoshiyuki 2017; Yi 2013) to ensure the successful production of the bronze vessels.

The selected raw material must match the tools available to the artisans, which can be the artisans’ hands (Liu et al. 2008), the sculpting chisels to form the motifs (Bagley 2009) the kilns used to fire the casting moulds. Examples of energy involve the artisan’s energy to move the raw material in processing and forming and the fuels used to fire the moulds. Knowledge or know-how ties the mentioned levels together in the sequence to produce the artifact (Sillar and Tite 2000). All of these levels must occur for the artifacts to exist the way we see them today. If there were a lack of any of the mentioned levels, the artifact would not exist. If there were any alterations to these levels, the artifacts would vary (Sillar and Tite 2000).

The variations and similarities in these choices are what is discernable as the sequence of production. The above levels focused on the first portion of the artifact’s life cycle. The artifact’s full life cycle involves its production, acquisition, use, and discard (Lemonnier 1986; Sillar and Tite 2000). These steps are directly linked to each other. Although discard had the least amount of influence on the production, this part of the artifact’s life cycle is directly involved in how archaeologists understand and perceive the artifacts.

Although the artisans were involved in producing the artifacts and the master of the five levels, external influences may also dictate the artifact’s production. Acquisition or transportation and use of the artifacts may determine the form or assembly of the finished product. The intended users may also alter the production, principally when the producer and user were likely different individuals. Artisans receive feedback from the consumers through the popularity of goods and adapt to increase their income and output (Sillar and Tite 2000).

The bronze vessels’ production goes beyond the producer and consumer relationship but involves the entire Shang society (Franklin 1999). The bronze vessels’ manufacture requires miners, smelters, artisans, and the elites for a successful production. The miners were individuals who collected the ores for the bronze made up of lead, tin, and copper. Smelters must refine the ores to extract these metals, while another artisan group combines them to produce the desirable alloys. The artisans also created the casting moulds while casting the bronze vessel forms. The elites were both the consumers of the bronze vessels and overseers to ensure access to the required raw materials, safe transportation routes for the raw materials, and commissioning the artisans for their work (Franklin 1999).

As Franklin (1999) focused on the more extensive bronze vessel production sequence, the casting moulds are a portion of the more extensive production sequence. However, studying the casting moulds focuse on one group within the larger society. The technological requirement and the artisan’s solutions become apparent by focusing on the artisans’ skills and how they solved the challenges of producing the bronze casting moulds.

There are two types of casting moulds uncovered from Anyang. ROM has these casting moulds in their collection, brought into the museum between 1935 and 1960 by Bishop White and donated to the museum by James Melon Menzies’s family after his death under Charles Trick Currelly’s direction (Shen 2015). According to the typological variations in both the casting mould types, vessel forms, and motif, Bishop White and James Menzies collected these casting moulds from the Anyang site (Nanba 2004).

This article will combine these concepts of the sequence of production and relate them to major spheres that the artisan bridges to produce the casting moulds. As the artisans produced the artifacts they must connect their geography, technological abilities, and consumer’s preferences (Fig. 2). Thus, connecting these spheres with the artisan in the center, while relating the different activities in the sequence of production to the three main spheres. Steps such as raw material is directly related to the geography and technological requirements, therefore intersecting these two spheres (Fig. 2). Forming of the mould to the type of vessels and motif is an indication of the converging technological and consumer spheres, in which the technological ability of the artisans and the preference of the consumers must meet in order to produce the artifacts (Fig. 2). The distribution of the artifacts and where the artisans were in association to the consumers in turn relates to geographical and consumer spheres. All of these activities occurred with the artisans in its center. The artisans must function within these spheres to ensure the production of the casting moulds.

Fig. 2
figure 2

The three main interactive spheres the bronze vessel artisans connect through the sequence of production. Mould production is dependent on the technological availabilities of the artisans such as kilns, other tools, and the production method. However, the bronze vessel form and the motif in this scenario is dictated by the consumers’ preferences and the technology available to the artisans. While the distribution of the moulds and bronze vessels are dependent on the artisan’s proximity to their consumers and whether they were controlled by the elites, therefore tying geography and consumer together

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4 Bronze vessel casting moulds from Anyang and the ROM

Li (2003) and Liu (2019) separated the casting moulds into two types (Type 1 and Type 2). These distinctions were significant based on these moulds, specifically the moulds’ exterior surfaces, thickness, and edges. Type 1 moulds are thin (Fig. 3B) with smooth exterior surfaces and some with protruding ribbings (Fig. 3 A). The ribbings made on the exterior surface were ovular, rectangular, and triangular in shapes. All of these casting moulds were produced with very fine fabric and fired in a reducing atmosphere.

Fig. 3
figure 3

Type 1 casting mould (ROM sample 960.238.414) (A) exterior surface – smooth and ribbed exterior surface, (B) edge - flat and thin, (C) interior surface – the location of the negative of the vessel form and motif when cast in direct contact with the molten bronze; Type 2 casting mould (ROM sample 949 × 143.111) (D) exterior surface – uneven with coarse material in this sample, (E) interior surface – location of the vessel form and motif

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There are two subgroups within the Type 1 casting moulds, motif and vessel form subtypes (Li 2007). The moulds categorized as motif moulds are banded moulds that only consist of the vessel’s motif section. The vessel’s shape and the undecorated portion are not present within the area the mould covers. Vessel form moulds incorporate both the motif and blank parts of the casting mould, making it easier to identify the types of vessels these casting moulds produced.

Type 2 casting moulds were far thicker than the Type 1 moulds, with a very irregular exterior surface (Fig. 3D) and mortise and tenons built into the moulds’ edges (Fig. 3E). There were two subtypes in this mould type as well according to the finish of the external surface. One subtype is less regular with indentations of tool or finger marks. In contrast, the second subtype indicates some crude attempt to smooth the casting moulds’ exterior surface and apply protrusions on the outer surface. Unlike the Type 1 moulds’ ribbings, these protrusions were near the exterior mould edges. Li (2007) suggested that the artisans made these protrusions as stabilizers during casting instead of aiding with the moulds’ alignment when assembled.

Type 2 moulds were also much thicker than the Type 1 casting moulds, with visible layers of silt material making up these casting moulds (Fig. 2E). There was coarser fabric on some of the exterior surfaces, while the artisans consistently used the fine fabric on the casting surface. Another vital attribute for Type 2 casting moulds is the mortise and tenons built on the edges. The mortise and tenons ensure a better alignment of the casting moulds when assembled (Liu 2019) and increase their durability during casting.

5 Two sequences of production for the two mould types

Studying these steps of the bronze casting moulds allow for further comprehension of the individuals involved and how they saw the task at hand. Each step selected has direct consequences and influences on how they will process these steps and how the following steps will begin. Although the individual steps are essential, how they relate to one another is crucial to comprehending the craft and the artisan’s thoughts.

Previous research on the bronze casting moulds was fragmentary and focused on specific steps without linking each step to one another. The combination of these steps is the key to production, not their parts. By focusing on one step within the sequence of production, the research loses the influences of this step to another. Although individual steps are essential, it is far more powerful when studied within the production chain between the two different mould types. As mentioned previously, the Anyang casting moulds represents two distinct mould types with some variation to the raw material, forming methods, and method of assemblage (Fig. 4).

Fig. 4
figure 4

Flow chart of the production method comparison between Mould Type 1 and 2 separated according to the different production steps discussed in this article

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This research will compare the two sequences of production, from its production to use, with portable microscope analysis, petrographic analysis, and scanning electron microscope analysis. This investigation focuses on the samples housed at the Royal Ontario Museum and combining this with various research conducted on the Anyang moulds to understand how the artisans met the requirements to produce a bronze vessel through the invention of piece moulds.

5.1 Procuring and processing raw materials

The beginning of the production sequence, often seen as the type of raw materials used to produce the artifacts, involves the artisans’ technological and geographical choices. The preferred raw material must meet the various criteria required throughout the production stages and the artisan’s accessibility to the raw material. Thus, to comprehend the artisan’s knowledge, we must see how the artisans bridge the technological to the geographical spheres in their choice of raw material and availability.

According to Freestone et al. (1989), Stoltman et al. (2018), and Yue et al. (2015), the casting moulds’ raw material was loess based on the minerals’ grain size and shape under microscopic analysis. Castain’s (2019) research on the Zhou dynasty casting moulds determined that the bronze casting mould raw materials were silt materials present in the loess deposits and the artisans likely used the paleosol. However, there is a lack of discussion on the geographical sphere in their analysis. Both Stoltman et al.‘s (2018) and Yue et al.’s (2015) analysis discussed the artisans using loess from local soil, but loess was not a deposit readily available in the Anyang landscape (Jeong et al. 2008; Liu 1985, 1988; You et al. 2013). Loess is also a vast expanse of aerosol deposit in Northern China, covering 6.35 × 105 km2 of land, north of 34–35° N latitude (You et al.2013). According to soil charts of the area (You et al. 2013) and loess research (Jeong et al. 2008; Liu 1988), the closest loess deposit was 300 km west beyond the Taihuang mountain (Fig. 5) (You et al. 2013). Thus, we have to revisit whether the artisans used loess for the raw material for the bronze casting in correlation to loess geographical distributions.

Fig. 5
figure 5

Anyang’s location in association to the loess plains (purple), Taihang Mountain and Beijing (Base map from google map, loess deposit according to You et al. 2013)

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Another issue with their discussion is the presence of two fabric types used to produce the casting moulds (Fig. 6). Petrographically, fabric is the combined materials making up the moulds such as clay, inclusions/temper, and voids. Fabric 1 is the fine well sorted fabric in silt sized grains (Fig. 6A) with very high quartz content. This is different from Fabric 2 (Fig. 6B), where larger inclusions with sand sized grains were also present in the silt sized grains.

Fig. 6
figure 6

Sample 960.238.426 taken in cross polarized light at 100x magnification. (A) Fabric 1 – fine well sorted fabric, (B) Fabric 2 – coarse and poorly sorted fabric

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Although Stoltman et al. (2018) and Yue et al. (2015) mentioned the coarse and fine fabrics on the casting moulds and the coarse material was due to the addition of temper, the alluvial deposition readily available around the Anyang site has natural sand grains mixed in with the silt deposited from the Yellow River (You et al.2013). However, the grainsize distribution of the coarse grains indicate natural sand inclusions instead of tempering (Fig. 7) due to the lack of bimodal distribution between the sand-sized particles compared to the rest of the samples. It is beyond this research to discuss the provenance of the raw material, but comparison beyond the grainsize is crucial in furthering our comprehension of the artisan’s choice in the raw material.

Fig. 7
figure 7

Grainsize and mineral comparison between Fabric 1 (graph on the left) and Fabric 2 (graph on the right) within ROM sample 960.238.426. Middle graph indicate the removal of coarse minerals from Fabric 2, indicating that the artisans may have removed the coarse minerals from the Fabric 2 but the artisans may have used another method to remove the softer minerals

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According to the grainsize comparison chart for Type 2 casting moulds between Fabrics 1 and 2, there is a direct correlation to their mineral composition and grainsize (Fig. 7). These similarities suggest that the artisans derived Fabric 1 from Fabric 2 through raw material refinement. The refinement involves the removal of the coarse grains from the raw material and removing denser materials such as carbonates. The artisans prefer the high silt material (Fabric 1) for the moulds’ casting surface. Fabric 2 was an uncommon raw material, only present on Type 2 moulds, and the artisans only used them as support material on the exterior surface of the Type 2 moulds.

The artisans selected the alluvial deposit and refined it with the purpose of the casting moulds in mind. The fine and uniformed grains with the high quartz content of Fabric 1 have many benefits for casting bronze vessels. First, the fine grains allow for retaining the motif’s fine details on the casting moulds either copied from the model or incised directly onto the mould surface (Liu 2019; Yue et al. 2016). However, this attribute is also available when working with leather hard clay. The advantage of using moulds with high quartz content is their high heat resistance (Tan 1999; Yue et al. 2016) and low warping tendencies (Freestone et al. 1989; Zhao et al. 2010). Silt-sized quartz is a significant advantage for the bronze casting mould because it has to withstand the direct contact of the molten bronze without changing form. If that were to happen, then the motif and the vessel form cannot be retained. The silt size material also allows for greater porosity (Zhao et al. 2010), allowing the gas to escape during casting. If the air cannot escape the mould during casting, the end product will result in holes in the bronze vessel’s walls, missing motifs, and scaling.

5.2 Shaping the casting moulds

The artisan’s choice in the raw material directly affects how they can form the moulds. The advantages of high silt-sized particles for The advantages of using high silt-sized particles were the greater ease in copying and retaining the fine motifs on the casting surface when producing the moulds and casting, while artisans added the coarse materials on the exterior to support the thin casting surface (Yue et al. 2016). This material is very different from the clay that most potters prefer to work with, requiring a different production method and knowledge to ensure the successful forming of the casting moulds and effective firing and use.

Due to the smooth exterior surface of Type 1 mould, the artisans cannot apply the force from the exterior surface towards the casting surface. The lack of orientation or direction of the grains and voids further supports the absence of pressure placed onto the Type 1 moulds (Fig. 8 A). Type 2 casting moulds with the distinct and definite orientation of the grains and voids parallel to the casting surface indicate compressional force by the artisans from the exterior towards the casting surface (Fig. 8B). This direction is the most evident from the layering of the samples’ fabric material (Fig. 8B). The lack of pressure in Type 1 moulds indicates the artisan’s preference to produce the motifs through incisions (Liu 2019).

Fig. 8
figure 8

Petrographic image taken at 100x magnification in cross polarized light Left: Type 1 mould (ROM Acc#949 × 143.112) lacking parallel orientation to casting surface (casting surface on right of picture, lack of vertical orientation); Right: Type 2 (ROM Acc#935.5.12) parallel orientation to casting surface (casting surface on bottom right of picture, distinct orientation of fabric and voids parallel to casting surface)

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Thus, the artisans had to invent different methods to create the same motifs based on the casting moulds’ overall forming method. The artisans invented two different methods to produce the same motif according to the casting mould types. The artisans also employed two different methods to assemble the casting moulds. Type 1 moulds consist of exterior ribbing that required an external material for alignment (not present in the analyzed samples), while the Type 2 mould artisans used mortise and tenons built on the edge to ensure proper alignment of the casting moulds (Liu 2019; Yue et al. 2016). These two alignment and assemblage methods reflect the artisans’ preferred forming method. Type 1 mould artisans formed the moulds through removal and smoothing, and Type 2 mould artisans used compression to form the mould and the mortise and tenons.

For Type 1 mould production, the artisans used stamping from the casting surface for Type 1 moulds to produce the swirl motifs, while compression of the mould material onto the model is sufficient in producing the swirl indentations on the Type 2 casting moulds. Despite the variation in production methods, the same motifs were present, indicating that the artisans may not be the ones to decide on the design, primarily when the artisans employed two different methods of production to produce the same motifs and vessel forms.

The variations in production did not overlap temporally during the latter half of Anyang’s occupation (Yue et al. 2016). The lack of a transitional stage of mould production between Type 1 and Type 2 moulds indicate two distinct artisan groups employed to form the moulds. Although the production method may vary between the two mould Types, the motif and vessel forms were consistent. The similarities in motifs between the two artisan groups can occur through close collaboration or the consumers’ preference. The identical motifs with different production methods suggest that the elites had more control or power over the type of vessels and motifs they intend to commission (Chang 1983; Franklin 1999), while the artisans were free to produce the casting moulds in different ways as long as they can achieve the same results. Thus, linking the geographical, technological, and cultural spheres.

5.3 Drying

Although forming and copying the motifs may be ideal with the right amount of water in the silt material, it also involves using the leather hard silt state. The leather hard state consists of less water in the silt material to make it less malleable. Although this state is much more challenging to form the mould, it is ideal for carving the motifs. The carving is less likely to smudge and better retain the crisp and detailed motifs in this state.

Interestingly, the artisans dried the moulds as a combined casting set for Type 2 moulds. Meaning the artisans assembled the piece moulds with the core for drying. This method is especially evident for Type 2 moulds due to the rope impressions on some of the mould’s exterior surfaces. Whether this was the same with Type 1 moulds is not discernable because the moulds’ outer material is no longer present. The cord marks on the exterior portions of some Type 2 moulds (Liu 2019) indicate cord marks. The moulds can only retain these cord impressions if the moulds were tied together when still wet. If they were tied together after the moulds were dry, the cords would not leave imprints on them. Thus, the artisans must have applied the cord onto the mould set before the mould was completely dry. Tying the piece moulds together during the drying step can ensure that the piece moulds dry together and reduce individual warping, and the piece moulds can still assemble flawlessly after drying.

Drying did occur, and the artisans must master and take advantage of the various states of drying to production the artifact. It is challenging to detect this step of production within the sequence since pottery and silt material dries naturally. This step may not require additional tools or infrastructures to assist this process. The artisans may encourage uniform drying by placing the moulds in a shaded area or under full sun, but this is not detectable archaeologically. However, the artisans were masters at controlling the different drying stages of forming and decrease warping.

5.4 Firing

The goal of firing the casting moulds was to ensure a successful casting. This must-have occurred in order for the casting moulds to stay intact after casting. This research analyzed two aspects of firing, the firing temperature and the atmosphere of firing. Both are essential factors to the casting moulds firing process and indicate the artisan’s comprehension and control of the firing technique. According to the mineralogical analysis, the artisans controlled both the firing atmosphere and temperature.

The artisans preferred firing the casting mould in a reducing atmosphere, evident from the grey colouration throughout. The reducing atmosphere results from sufficient carbon around the casting moulds during the firing with complete carbon penetration throughout the thickness of both mould Types 1 and 2. The atmosphere indicates a very controlled firing in which the artisans encouraged smoke around the moulds while having enough oxygen around the fire to warrant burning. To ensure this firing method, the artisans most likely employed kilns. Kilns allow for the separation of the atmospheres between the mould and the fire and better control of the firing atmosphere.

Based on micas, carbonates, and shells’ characteristics, the firing temperature occurred between 850 and 950 °C range. This identified range was according to mineralogical characteristics and their reaction to firing temperatures. Micas begin to lose hydroxyls between 600 and 800 °C, visible in the crystal layers’ splitting under the petrographic microscope (Fig. 9). If the fire exceeds 900–1000 °C, the crystal structures will completely separate and lose their birefringence (Quinn 2013). The lack of crystalized structure of carbonates further suggests the firing temperature was above 800 °C (Kompan ́ıkova ́ et al. 2014), while the scanning electron image of the shells’ microscopic porosity (Fig. 10) coincides with samples fired between 850 and 950 °C when compared to Maritan et al.‘s (2007) shell firing research. These firing attributes indicate the artisans used consistent and controlled firing methods between both of the mould types.

Fig. 9
figure 9

Split mica taken in sample 949 × 143.108 (Fabric 2) under plain polarized light at 600x magnification indicating the firing temperature occurred between 600–800 °C

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Fig. 10
figure 10

Shell microstructure in sample 949 × 143.66 (Fabric 2) taken under SEM at 500x magnification the porosity coincides with firing temperatures between 850–950 °C (Martian et al. 2007)

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5.5 Using the moulds for casting

Not all of the casting moulds resemble completely reduced firing. However, this is the result of the mould casting process instead of firing. Through experimental archaeology done by the author in bronze casting, the moulds must be fired at a consistent temperature to ensure successful casting of simple bivalved bronze casting tool mould. Thus, if the casting occurred without external heat on the casting moulds, the bronze will solidify too quickly, resulting in failed casting of the vessel forms or the motifs.

The presence of a uniformed reducing atmosphere on the casting surface combined with the mixed firing atmosphere on the moulds’ exterior surface is a sign for bronze casting. This phenomenon is present in both Type 1 and 2 moulds. Type 2 mould had more dramatic oxidization than those found in Type 1 due to the lack of the original exterior mould material for Type 1 moulds. The molten bronze in contact with the mould resulted in a thin layer of reducing atmosphere is left behind on the casting surface. Mottling of the firing atmosphere indicates little control of the atmosphere during the second firing and likely occurred in an open fire pit instead of a kiln for casting ease.

6 Discussion

These two moulds were employed to produce the same vessel forms (jue, Jia, gu, ding, gui, zhi, yi, you) and the motifs too overlapped between the two different moulds (Li 2007; Liu 2019). However, there are some preferences for smaller vessels for Type 1 moulds compared to Type 2 moulds (Yue et al. 2016). The similar vessel forms and motifs on the casting moulds indicate that the artisans could produce the same objects with different production methods. Although the choices made by the artisans may pertain to the production method, the elite consumers likely dictated the form and the preferred motif on the bronze vessels.

According to the sequence of production, it is clear that there are convergence and divergence of techniques within the bronze casting mould production. It indicates some shared knowledge and resources between the bronze casting mould artisans. Although there were two distinct mould types with different forming methods, which suggests two groups of artisans for this step, they shared similar attributes to specific production steps in the raw material and firing method.

Due to the two forming methods, these two production methods were distinct methods employed by two artisan groups. However, it is unclear whether the separation continued in the raw material processing, firing, and casting. The artisans in both groups had access to Fabric 1, the highly refined casting mould material. This access indicates shared resources, either in the knowledge of raw material refinement or access to the material made by artisans who specialized in raw material refinement was passed down from the artisans who made the Type 1 moulds to the artisans who made the Type 2 moulds.

The lack of overlapping method in forming between the two mould types temporally (Yue et al. 2016) suggests that the artisans who formed the Type 2 moulds replaced the Type 1 mould artisans by the end of Anyang Phase II with no indication of a transitional phase between Type 1 and Type 2. If the same artisans who produced the Type 1 moulds invented the Type 2 moulds, some transitional forms should be visible within the archaeological assemblage, but this is not visible in the archaeological assemblage found to date.

In contrast, the raw material refinement and firing method were consistent throughout the Anyang occupation. The consistency of these two production methods suggest that different artisan groups likely managed the raw material preparation and firing. Thus, the artisans of these two groups used the same methods over time, while the mould-forming artisans did not.

The shared resources such as raw material and kilns indeed indicate sharing of knowledge and resources. Thus, the separation of casting mould production may be more complicated than having two artisan groups indicated by the mould types. Within the sequence of production, there was a division of labour between raw material refinement, forming, and firing.

7 Conclusion

By mapping out the casting moulds’ sequence, the artisans behind the artifacts become visible. The artisans were masters in making the bronze casting moulds and the technological advantages to the materials they have selected, formed, and used. These artisans, who produced the elites’ artifacts, had their specialties and contribution to the ancient Shang society. The sequence of production indicated very specialized production with some division of labour.

To be a bronze casting mould artisan in late Shang dynasty Anyang, they must know the right material for the moulds and have access to or refine the fine silt material. The forming method is specialized, and they must learn to work with the fine silt material to produce the ideal vessel form and motif. Then it must be assembled well to ensure proper fitting for casting. Thus, bronze casting mould making is a very skilled production requiring extensive knowledge from the raw material to the final casting.

Although the artisans left no trace in the written records, their legacy lies in the elites’ awe-inspiring bronze vessels and the casting moulds’ technological marvel. Without the artisans’ knowledge and their social interactions, the Shang dynasty’s symbol of prestige and an object that symbolizes China would not have come into being. The artisans’ knowledge and specialization are present in every line on the mould and the production choices. Their identity is not the power they wield over the masses like the elites, but their ingenuity and ability to bridge the geography, technology, and culture into physical objects.