1. INTRODUCTION
The shrine of Gyeongmogung (景慕宮), constructed in 1789, was built to enshrine the spirit tablet of Crown Prince Sado. It was built in the year that King Jeongjo was crowned. In 1899 (the third year of Gwangmu), the spirit tablet of Crown Prince Sado was removed from Gyeongmogung to Jongmyo, and the shrine lost its primary function as a memorial site. In 1908 (the second year of Yunghui), Yeonghuijeon Hall (永禧殿) was constructed. However, this building was destroyed during the Japanese colonial period or the Korean War (Korea Heritage Service, Kyujanggak Institute for Korean Studies at Seoul National University). The Korea Cultural Heritage Foundation (now known as the Korea Heritage Agency) conducted an additional excavation at the Gyeongmogung Shrine Site in Seoul in 2011. The excavation area, located on the periphery of the Jeongjeon area excavated in 2010, is divided into two sections. In Section B, including the Jeongjeon area, in which traces of Yeonghuijeon remain, four white porcelain lidded bowls (baekja hap) were discovered near Wall Site No. 2. These baekja hap are presumed to be jindangu, or protective ritual deposits associated with ceremonies performed during construction of the building (Korea Cultural Heritage Foundation, 2013).
A jindangu (鎭壇具) is a ritual deposit buried within or around the foundations of structures, including buildings, pagodas, and tombs, to ensure the safety of the construction. This phenomenon emerges from a fusion of indigenous Korean spiritual beliefs and Taoist concepts of earth deities (地神) with Buddhist rituals. Evidence of the use of protective ritual deposits dates to the Neolithic period, where rim and body fragments of ritual pottery used in foundation ceremonies appear to have been discovered at residential sites from that era (Chungnam National University Museum, 2006). Artifacts associated with the jindangu from throughout the Joseon dynasty have been excavated in various regions of Korea. Such vessels often contain materials such as lacquer, cinnabar, charcoal, glass beads, pottery, metallic objects, animal bones, grains, and nuts.
Where the vessel was found empty, it has been suggested that organic materials, particularly food offerings, might have been placed inside (Oh, 2013; Park, 2017). This practice continued into the Joseon era, with documented cases of jindangu being buried in the construction of buildings built in honor of prominent individuals or in public structures (Park, 2017).
This study investigated the composition of artifacts placed inside protective ritual deposits. This analysis focused on black residues found in white porcelain lidded bowls. These materials were discovered by the Korea Cultural Heritage Foundation during a 2011 investigation of the Yeonghuijeon Hall site in Seoul. This research enhances our understanding of architectural rituals and cultural practices in the Joseon era.
2. MATERIALS AND METHODS
2.1. Samples for analysis
As part of the restoration project for the Gyeongmogung Shrine Site in Seoul (designated Historic Site), the Korea Cultural Heritage Foundation conducted additional excavation from September 14 to November 4, 2011. The excavation focused on the peripheral areas of the Jeongjeon, and several features were identified, including the inner wall (Wall Site No. 2). White porcelain lidded bowls were located near the rear (west side) of the Iancheong Hall, with the Subokcheong located south of the main gate (Sinmun Gate), as well as a drainage system. In addition, remnants of walls and buildings constructed during the early Joseon period were uncovered (Figure 1).
The white porcelain lidded bowls were buried in a single row in a pit that was 95 cm long, 20 cm wide, and 8 cm deep, located approximately 50 cm east of the central point of the wall (Figure 2A). The bowls were partially damaged during excavation, and carbonized materials were found inside them (Figure 2B) (Korea Cultural Heritage Foundation, 2013).
In this study, residual materials (Figure 2C) were collected from the insides of four porcelain bowls excavated near Wall Site No. 2. Additionally, as an experimental group sample for fourier-transform infrared spectroscopy (FT-IR) analysis, soil from the interior of a reddish-brown earthenware jar was excavated near the southern foundation of the main gate (Sinmun Gate) was used (Figure 2D). Four white porcelain lidded bowls contained unidentified black residues that appeared carbonized (Figure 3). Such residues were extremely fragile and easily crumbled under even slight pressure. During sampling for analysis, the material rapidly fragmented into irregular and various sized pieces.
2.2. Surface microanalysis
The samples were dried to 40% relative humidity at room temperature. Surface and morphological observations were conducted without additional pretreatments, such as washing or coating, using a stereomicroscope (Stemi 2000-C, Carl Zeiss, Germany) and a tabletop scanning electron microscope (TM3000, Hitachi, Japan). The stereomicroscope was used at magnifications that ranged from ×0.65 to ×1.2. The tabletop microscope was operated in back-scattered electron image mode, at magnifications ranging from ×30 to ×800, with an accelerating voltage of 15 kV.
2.3. Elemental analysis
Scanning electron microscopy with an energy-dispersive spectrometer (SEM-EDS) was conducted to identify the composition of a metallic sample that was presumed to have been excavated from the second lidded bowl. The sample was analyzed without pretreatment, following the same procedure as that used for observations using a tabletop SEM (JSM-5910LV, JEOL, JPN) equipped with an EDS (7324, Oxford instruments, UK). Observations were performed in the secondary electron image (SEI) mode at a magnification of ×250, with an accelerating voltage of 20 kV.
2.4. Infrared spectroscopy analysis
FT-IR was used to identify the functional groups of the organic materials present in the samples. For this purpose, the samples were finely ground with an agate mortar and loaded onto a diamond crystal for analysis using attenuated total reflection (ATR) method. FT-IR ATR analysis was conducted with an infrared spectrometer (Nicolet iS5, Thermo Fisher Scientific, US). The parameters of the analysis included a spectral range of 4000–650 cm−1, a resolution of 4 cm−1, and 16 scans.
3. RESULTS
3.1. Stereomicroscopic observation
Stereomicroscopic observations showed that all samples from the white porcelain lidded bowls had a thin, layered, and plate-like structure (Figure 4). Some samples separated from the thicker layers displayed a glossy surface. However, further analyses were limited because the residues adhered to the surrounding material. In contrast, the residues from Porcelain Bowl 2 exhibited a distinct combination of smooth, flat surfaces and woven fiber patterns (Figure 4B, red arrow). Notably, a gold-colored substance was identified between these two areas (Figure 4B, yellow arrow).
3.2. Scanning electron microscope analysis
Microscopic observations using a tabletop scanning electron microscope showed that most of the residues featured a plate-like structure, which was consistent with the findings of stereomicroscopic analysis (Figure 5A). The surface of this structure appeared to be smooth and flat, and the internal fibers were densely packed, arranged in an irregular pattern. Individual fibers had diameters ranging from approximately 5 to 15 μm. No distinct nodes were observed, although the fibers displayed multiple branches that formed a complex and intertwined network. Furthermore, the characteristic features of the animal fibers, such as cuticle scales, medullas, and distinct basal and terminal structures, were absent (Figure 5B, 5C). From these morphological features, it can be inferred that the plate-like structure is plant-based and likely processed through the extraction of fibers, followed by artificial flattening.
SEM-EDS analysis was conducted on micro-areas that exhibited a metallic sheen in the residues from Porcelain Bowl 2 (Figure 6). The surface analysis by EDS identified that gold (Au) was the primary component. In contrast, elements that are commonly associated with soil (e.g., Si and Al) and organic matter (e.g., C and O) were not detected. The gold-colored residue was predominantly composed of gold, with minimal contamination from soil or organic sources.
3.3. Infrared spectroscopy analysis
To investigate the differences between samples from the porcelain bowls, FT-IR analysis was performed using the ATR method, with a diamond crystal (Figure 7). The analyses showed that both the residues inside the porcelain bowls and the experimental earthenware sample featured prominent peaks at 1000–1050 cm−1 and 900 cm−1. These peaks can be attributed to the stretching vibrations of P-O-C (Pavia et al., 2001), likely originated from the humic substances present in the soil. The observation of similar spectra in the soil of the experimental group supports the conclusion that these components are soil derived.
By contrast, spectral peaks near 1600 cm−1 and 1350– 1380 cm−1 were exclusively detected in residues from porcelain bowls and were absent from the experimental group soil. In the samples, the residues from Porcelain Bowl 2 showed characteristics that were distinct from those of the others. These peaks correspond to N-H bending vibrations (1600 cm−1) and C-N stretching vibrations (1350–1380 cm−1) (Pavia et al., 2001). However, characteristic protein-specific spectra, such as amide Ⅰ (1600–1700 cm−1), amide Ⅱ (1500 –1600 cm−1), and amide Ⅲ (1200–1300 cm−1), which are typically observed in degraded silk textiles, were not detected. Therefore, it is difficult to conclusively attribute these peaks to the amine groups.
4. DISCUSSION
The residues recovered from the white porcelain lidded bowls excavated at the Yeonghuijeon Hall showed plate-like structures composed of plant-based fibers. These fibers, which were characterized by branches, appeared to have been artificially flattened and compacted into a dense, thin form that resembled the features of paper. Although the specific plant species from which these fibers originated could not be identified, comparisons with the raw materials and paperproduction techniques used during the burial period of the protective ritual deposit may provide a scientific basis for the interpretation of these plate-like structures in future studies.
The residues in porcelain bowls 1, 3, and 4 were highly fragile, making them unsuitable for sampling and further analysis. By contrast, the residues from Porcelain Bowl 2 could be observed under a stereomicroscope and were found to consist of more than two types of materials, enabling the separation of plate-like structures for further analysis. In the samples, fiber bundles of approximately 7 mm in length were identified (Figure 8A). These fibers appeared to be hair-like bundles under stereomicroscope, and SEM revealed that the fibers had an average diameter of approximately 10 μm, showing a consistent twisting pattern along their lengths (Figure 9A). Cross-sectional observations produced predominantly C-shaped or U-shaped structures, with some fibers displaying lumens, which are characteristic of plant-based fibers (Figure 9B). However, no branches, nodes, or scale structures characteristic of animal fibers was observed.
Two distinct types of fabric structure were identified in stereomicroscopic analysis. Both samples showed smooth, sleek surfaces (Figure 8B, C, yellow arrow). SEM observations of the cross-sections showed irregular triangular shapes, with diameters ranging from 7 to 10 μm, which suggests that the fabric was composed of degummed silk (Figure 9D). One sample (Figure 8B) was measured at approximately 3.6 mm long, with weft spacings that ranged irregularly from 50 to 350 μm. Detailed SEM analysis showed that the fabric employed a leno weave structure, in which pairs of warp threads twisted around the weft threads to create a crossing pattern (Figure 9C). The other sample (Figure 8C) was identified as a plain weave fabric and was blackened, with swollen marks on its surface, consistent with the combustion of silk or wool fibers. Cross-sectional observations revealed indistinct boundaries within the fiber bundles, which further confirmed the presence of degummed silk.
5. CONCLUSION
This study reports the results of a scientific analysis of residues recovered from white porcelain lidded bowls excavated near Wall Site No. 2 at the Yeonghuijeon Hall site. The analysis identified plant- and animal-based fibers from the charred samples of the porcelain bowls. Based on the inferred purpose of the baekja hap (white porcelain bowls) and the results of this study, it is hypothesized that the bowls contained both paper materials and textiles, namely, silk or cotton.
However, the analyzed samples represent only a subset of the residues, so it cannot be conclusively determined that the materials that were deposited in the bowls were limited to four categories, including gold foil. Likewise, the presence of animal-based fibers in Porcelain Bowl 2 did not preclude the possibility that these fibers were present in other porcelain bowls. Most observed residues were charred, characterized by significant deterioration due to long-term degradation, producing substantial loss of their original form. Further, due to the susceptibility of organic materials to heat and decomposition, it is plausible that certain items that were deposited in the white porcelain bowls no longer remain.
To comprehensively investigate the items that were deposited in the white porcelain bowls, an interdisciplinary approach that combines historical studies of the period’s cultural context with archeological analysis of the morphological characteristics and locations of the burial of the four baekja hap is essential. Future research should include a comparative study of contemporary paper materials and textiles from the same period to contextualize this study’s findings.
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