Study on the Surface Coating Techniques of Furniture in the Long’en Hall of Qing Changling Mausoleum

Abstract

As a core structure within the Qing Changling Mausoleum, a UNESCO World Cultural Heritage site, Long’en Hall preserves a relatively complete set of Qing dynasty imperial lacquered furniture. These furnishings provide critical physical evidence for studying Qing dynasty sacrificial rituals and the craftsmanship of court lacquerware. However, limited research has been conducted on the surface finishing techniques of such furnishings, posing challenges to their conservation and accurate restoration. This study focuses on representative furnishings from Long’en Hall—including an offering table, an incense pavilion, a throne, and a poke lamp—and employed a multi-method analytical approach comprising fluorescence microscopy (FM), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared (FTIR) spectroscopy. The analysis was conducted on the following two levels: the lacquer layer structure and material composition. The results show that the furnishings in the Long’en Hall adopt the typical structure of “lacquer ash layer–color lacquer layer”, and the color lacquer layer is composed of raw lacquer, tung oil, animal glue, and other natural organic ingredients as film-forming materials, supplemented with inorganic mineral pigments such as red lead (Pb₃O₄) and Au metal, which constitutes a stable organic–inorganic composite structure with the lacquer ash layer. The multi-analysis results show a good complementary and cross-corroboration relationship, providing the necessary technical support and a theoretical reference for Qing dynasty palace lacquer wood furniture as cultural relics worthy of scientific protection and imitation.

1. Introduction

The Qing Changling Mausoleum is the burial site of Emperor Jiaqing and Empress Nuhulu of the Qing dynasty. As a significant component of the Qing imperial mausoleum system, Changling holds high historical and cultural value and has been designated as a UNESCO World Cultural Heritage site [1]. It is currently the only imperial tomb in the Western Qing Tombs open to the public and features a relatively well-preserved architectural complex. Long’en Hall retains many original Qing dynasty palace furniture and furnishing examples among its structures, providing valuable physical evidence for studying the Qing court’s sacrificial system and artisanal techniques.

According to archival sources such as the Qing Hui Dian (The Collected Statutes of the Qing Dynasty) and Qinding Libu Zeli (Imperially Commissioned Ritual Regulations of the Ministry of Rites), Long’en Hall served as the principal venue for daily and seasonal sacrificial ceremonies conducted by the imperial family [2,3]. Functioning as a spiritual extension of the ancestral temples in the capital, it upheld the legitimacy of imperial authority through ritual. The furnishings of Long’en Hall—including incense pavilions, offering tables, thrones, and poke lamps—were integral ritual instruments. Their specifications, arrangement, lacquer patterns, and color schemes reflect the Qing emperors’ hierarchical rank and ceremonial norms, thus holding considerable academic and cultural value.

With time, these furnishings have suffered from environmental exposure, light-induced degradation, and human activity, resulting in visible aging phenomena such as cracking, delamination, and discoloration of the lacquer coating [4]. However, despite their significance, scholarly research on the materials and techniques used in their surface finishing remains limited. This lack of systematic understanding hampers scientific restoration and reproduction efforts and hinders the preservation and transmission of Qing imperial lacquer craftsmanship.

Restoration practices for relics from Qing imperial tombs—including Changling—primarily rely on historical technical records such as the Craftsmen’s Regulations (Jiangzuo Zeli) and Workshop Archives (Huoji Dang). However, dated terminology and discrepancies between historical and contemporary language often lead to semantic ambiguities and misinterpretations of processes, making these records insufficient to meet the precision standards required in modern restoration and replication.

Given these challenges, this study focuses on the lacquer finishing techniques of typical furnishings preserved in Long’en Hall. Representative surface samples were collected from incense pavilions, offering tables, thrones, and poke lamps. A comprehensive analytical approach—incorporating fluorescence stereomicroscopy (FM), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared (FTIR) spectroscopy—was employed to examine both the structural characteristics of the lacquer layers and their material composition. The goal was to reveal Qing imperial lacquer craftsmanship’s technological and material features and provide a scientific foundation for heritage protection, technical restoration, and cultural transmission.

2. Materials and Methods

2.1. Material Source

The samples tested in this study were obtained from the furnishings in the Long’en Hall of the Qing Changling Mausoleum, which included an offering table, an incense pavilion, a torch lantern, and a gilded throne (Figure 1). The sampling parts are shown in

Table 1. Sampling record sheet for Long’en Hall furnishings.

Furniture Name	Sampling Location	Sampling Method	Pre-Sampling Photo	Post-Sampling Photo	Visible Color
Offering Table	Tabletop of the offering table	Scraping of the cracked lacquer layer			Reddish-gray surface; semi-transparent waxed surface on top
Offering Table	the underside of the right horizontal brace	Scraping of the cracked lacquer layer			Red
Incense Pavilion	the upper interior of the incense pavilion	Collection of the fallen lacquer layer			Red
Torch Lantern	Tenon block for positioning the lamp peg	Scraping of the cracked lacquer layer			Reddish-gray
Gilded Throne	Rear right section of the throne	Scraping of the cracked lacquer layer			Bright golden
Gilded Throne	Lower right Badama area of the throne	Scraping of the cracked lacquer layer			Bright golden

.

Sampling sites were selected with full consideration of the lacquer layer’s integrity, representativeness, and the influence of furniture use on surface preservation. Samples were mainly taken from areas with complex finishing and well-preserved coatings, such as the upper surface of the offering table, the stop blocks of Torch Lantern, the inner top of the incense pavilion, and the rear side of the throne (see Table 1). These areas often feature thicker lacquer ash and multilayer color lacquers to better resist humidity and low-light conditions.

To minimize damage and visual impact, sampling was carried out in hidden or less noticeable areas, such as the back or corners of the furniture. All procedures were conducted under the supervision of the Department of Cultural Relics Conservation, following the principles of minimal intervention and reversibility.

2.2. Test Methods

In this study, we used a body-view fluorescence microscope (FM), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), X-ray electron spectroscopy (XPS), and Fourier-transform infrared (FTIR) spectroscopy to observe and analyze different parts of the samples of the lacquer layers of the furnishings in Long’en Hall. The relevant information is shown in

Table 2. Experimental instruments and testing parameters.

Testing Order	Instrument Name	Brand/Model	Main Application	Technical Specifications and Testing Conditions
1	Stereo Fluorescence Microscope	Leica M205FA (Leica Microsystems, Wetzlar, Germany)	Microscopic observation of the sample surface and cross-section	Fully apochromatic optical system; zoom ratio of 20.5:1; magnification range 7.8×–160×, configurable up to 1280×; large depth-of-field structure visualization
2	SEM-EDS	Regulus8100 (Hitachi, Tokyo, Japan)	Elemental composition analysis of sample cross-sections	EDS detection range: Be to Am; energy resolution better than 129 eV for Mn Kα (at 100,000 CPS); 57 eV for C-K and 67 eV for F-K; supports elemental mapping, line scanning, and area distribution analyses
3	X-ray Photoelectron Spectrometer (XPS)	K-Alpha (Thermo Fisher Scientific, Waltham, MA, USA)	Non-destructive analysis of surface elemental composition and chemical states	Al Kα monochromatic X-ray source (1486.6 eV); max power: 72 W; vacuum better than 2 × 10−7 Pa; spot size: 400 μm (in area analysis mode); pass energy: 50 eV (elemental scan) and 20 eV (high-resolution scan); step size: 0.1 eV; charge compensation using dual-source low-energy electron and Ar+ ion
4	Fourier-Transform Infrared (FTIR) Spectrometer	Nicolet iS10 (Thermo Fisher Scientific, USA)	Analysis of organic/inorganic components of lacquer ash layer and surface lacquer layer	Mid-infrared range: 400–4000 cm−1; 32 scans; resolution: 4 cm−1; non-destructive testing

.

3. Results and Discussion

3.1. Cross-Sectional Observation and Analysis with a Fluorescence Stereomicroscope

A Leica M205FA fluorescence stereomicroscope was employed to observe the microstructure of the samples at 50× magnification, with the specimens mounted in an inverted orientation. The following cross-sectional observations were revealed (see

Table 3. Cross-sectional observation of samples.

Sample Source	Upper Lacquer Layer Color and Thickness	Characteristics of Lacquer Ash Layer	Sample Cross-Section
Offering Table	Red lacquer (~70 μm) + dark red lacquer (~125 μm)	No distinct stratification; the lower layer was rough and contained mineral particles
Incense Pavilion	Red lacquer layer (~80 μm)	Two sublayers: yellow (fine texture, ~350 μm) and gray (slightly coarse)
Torch Lantern	Red lacquer layer (~150 μm)	Similar to the incense pavilion, with a yellowish-brown and gray dual-layer structure
Throne (Lower Rear Right, Badama Area)	Black lacquer layer (~250 μm) + underlying red lacquer	No obvious lacquer ash layer
Lower Right Side Of The Throne	Black lacquer layer (~90 μm) + underlying red lacquer	No obvious lacquer ash layer

).

The offering table, incense pavilion, and Torch Lantern samples from the upper layer of the red lacquer layer and the lower part of the black layer were mixed with stone-like particles. The lower part of the upper layer was rougher, and the traditional lacquer process of a coarse gray to a pleasing gray lacquer decorative substrate effect was closer to the performance of the process [5]. In the offering table sample, the red lacquer layer could be divided into two parts according to the variation in color depth, and it was speculated that part of the dark color may be due to the penetration influence of the lacquer’s gray-like substance close to the lower layer [6]. The beige color of the ground layer of both the incense pavilion and the Torch Lantern was speculated to be the result of a yellowish component of the traditional lacquer ash, which was usually used to increase the adhesion of the lacquer dust or a glutinous rice paste.

The samples from the lower rear of the throne, the Badama, and the right rear did not show any obvious distribution of lacquer ash layers, so it was assumed that these samples may not have been primed with similar lacquer ash substances. In addition, the curved shape of the right rear Badama was related to the curved shape of the actual decoration (see Table 2).

3.2. Elemental Analysis of Sample Cross-Sections by SEM-EDS

Based on microscopic observations of the sample sections, we performed a scanning electron microscopy–energy spectroscopy (SEM-EDS) analysis of the lacquer layer sections of the samples from the offering table, incense pavilion, poke lamp, and throne from the Long’en Hall of the Qing Changling Mausoleum (Figure 2). It is important to note that the gold (Au) detected in the spectra may have originated from the gold sputtering applied during the sample preparation for the SEM analysis. Thus, it held no significant reference for the original material composition.

The EDS analysis revealed that carbon (C) and oxygen (O) were the predominant elements detected in the lacquer layer samples, indicating a high content of organic substances [7]. This finding is consistent with historical records of traditional lacquerware production.

In the samples from the offering table, incense pavilion, and torch lantern, elements such as silicon (Si), aluminum (Al), and calcium (Ca) were detected. These elements are typically associated with materials commonly used in traditional lacquerware foundation layers, such as clay, fabric-based bonding layers, and silicate mineral additives, which enhance the adhesion and structural stability of the lacquer film [8]. Additionally, lead (Pb) was detected in both the incense pavilion and offering table samples, suggesting its possible use as a coloring agent for the red surface lacquer layer. In ancient polychrome lacquer techniques, red lead (Pb₃O₄) was not only used as a red pigment but was also often mixed with transparent lacquer to achieve a dyed effect [9]. The incense pavilion sample exhibited relatively high levels of Si, Al, Ca, and Pb, along with a trace amount of magnesium (Mg; 0.82%). These results suggest the use of silicate-based fillers such as wheat starch powder, brick ash, and red lead in the foundation layer, as corroborated by multiple archival records from the First Historical Archives of China, including the Repair Expense Ledger of the Incense Pavilion in the Yangxin Hall (Guangxu, 31st year) and the Construction Expense Record of the Incense Pavilion (Xuantong, 1st year), both of which document the standardized application of such materials in Qing ritual lacquerware.

Moreover, the cross-sectional EDS analysis of the offering table, incense pavilion, and torch lantern samples repeatedly detected the presence of tungsten (W), an element rarely found in traditional lacquerware. This anomaly is currently attributed to possible external factors, such as the incorporation of restoration materials or contamination from specific tools or environments.

A trace amount of sulfur (S; 0.08%) was also detected in the torch lantern sample. Although the content was low, it may have originated from sulfide compounds naturally present in raw lacquer [10].

In contrast, the gilded throne sample contained only minor amounts of inorganic elements such as Al, Si, and Ca, aside from C and O. This suggests that the use of inorganic fillers in this lacquer layer was minimal. The result was consistent with preliminary microscopic observations and further supports the inference that the gilded throne may not have had a lacquer foundation technique applied.

3.3. XPS Analysis of Surface Elements

Following the cross-sectional EDS analysis of the offering table, incense pavilion sample, torch lantern, and gilded throne, X-ray photoelectron spectroscopy (XPS) was conducted on the surface of the lacquer layers to further investigate the composition of the colored lacquer coatings. Based on parameters such as peak positions, peak areas, and full width at half maximum (FWHM), the elemental composition and chemical states of the surface components were analyzed [11]. The XPS analysis was performed on untreated, non-electroplated samples to ensure the purity of the test surfaces.

The C 1s spectra (Figure 3) exhibited characteristic peaks at binding energies of approximately 284.79–284.80 eV (C–C/C–H), 286.33–286.52 eV (C–O/C–N), and 288.32–288.77 eV (O–C=O). Among these, the peak corresponding with aliphatic hydrocarbon chains (C–C/C–H) exhibited the most significant area, indicating that the primary structural component of the lacquer film was derived from natural lacquer (urushi) or similar resinous substances [12]. Oxygen-containing functional groups such as hydroxyl and carboxyl are closely related to the phenolic structure of urushiol, the main constituent of natural lacquer, and the oxidative degradation products formed during aging.

The O1 spectra were centered around 532.08–532.21 eV. The relatively broad peak widths and large peak areas indicated a high concentration of oxidized functional groups within the lacquer film matrix, such as ethers, carboxyls, and hydroxyls (Figure 4) [13].

The N1s signals appeared within the 399.69–400.81 eV range, suggesting the possible presence of nitrogen-containing substances. These could include additives such as swim bladder glue, animal-protein-based binders, plant-derived gums, and fiber-rich components like flax thread (Figure 5) [14].

In the S2p spectra, two distinct peaks corresponding with low-valence (162–163 eV) and high-valence (168–169 eV) sulfur states indicated a dual origin. Sulfur can derive from mineral pigments or plant ash and may also have participated in the curing and pigmentation processes of the lacquer layers (Figure 6) [15].

The Pb element was detected with relatively weak signals in the XPS spectra, appearing only on the surface of the offering table and incense pavilion samples. Its binding energy is consistent with lead-containing compounds such as PbO or PbS. Given that Pb was also identified in the EDS cross-sectional analysis of these samples, its surface localization, as revealed by XPS, further supported the hypothesis that lead-based pigments—such as red lead (Pb₃O₄)—may have been intentionally used as colorants in the lacquer layers. Alternatively, trace amounts of Pb may also have originated from the drying oil additives employed in traditional lacquer formulations [16] (Figure 7).

Notably, only a weak Au 4f peak was observed in the throne sample from the Hall of Long’en, with a binding energy at 88.78 eV and an integrated peak area of 1430.91 CPS·eV, corresponding with an atomic concentration of just 0.04% (Figure 8). However, the fluorescence stereomicroscope at 50× magnification revealed surface characteristics consistent with the appearance of the “red gold” used in Qing dynasty gilded lacquerware (Figure 8). This suggests that the throne was originally decorated with gold lacquer.

According to the Craftsman Regulations (Jiangzuo Zeli), the production process for gold lacquered furniture, such as that used in Fengxian Hall, involved the application of gold over a lacquer base, followed by a transparent lacquer coating. It was, therefore, inferred that the gold layer may have been encapsulated beneath the surface lacquer, rendering it less detectable by XPS, which typically probes only the outermost nanometer-scale layer of a sample [17].

In addition, we also considered the possibility of the use of copper–zinc alloys in the gold lacquer throne and performed XPS on two elements, Cu and Zn. Unfortunately, there was no binding energy signal for these two elements in the test results.

3.4. FTIR Analysis

To comprehensively reveal the material composition of the lacquer decoration structure of the offering table in Long’en Hall of the Qing Changling Mausoleum and its technological characteristics, and to supplement the validation of the EDS and XPS analysis results, a Fourier-transform infrared (FTIR) spectroscopy analysis was performed on the contact surface (lacquer ash layer) and surface color lacquer layer (red lacquer and gold lacquer layers) of the samples from the offering table, incense pavilion, poke lamp, and throne, respectively, to analyze the organic and inorganic compositions and functional positioning of the material samples.

3.4.1. FTIR Analysis of the Lacquer Ash Layer

The FTIR absorption peaks for the lacquer ash layer are shown in Figure 9.

As summarized in

Table 4. Characteristic absorption peaks of the lacquer ash layer, their corresponding chemical bonds/functional groups, and literature references.

Absorption Peak Position (cm−1)	Corresponding Chemical Bond/Group	Characteristics of Lacquer Ash Layer
3544.52; 3396.03	O–H and N–H stretching vibrations	Records of Paint Decoration; animal glue
1644.98; 1522.42	N–H bending; C=O stretching
2921.63; 2852.20	C–H stretching vibrations
1114.65; 1002.80	C–O stretching vibrations	Records of Paint Decoration; lacquer ash process
1417.42; 1319.07	Carboxylate/carbonate
676.41; 470.32	Si–O and Al–O bending vibrations	Records of Paint Decoration; section on color and texture

, the infrared spectral analysis of the lacquer ash layer revealed characteristic absorption peaks corresponding with O–H and N–H stretching vibrations, indicative of proteinaceous materials, which may have originated from animal-based adhesives such as pig’s blood glue or swim bladder glue [18]. Peaks associated with C–H and C–O stretching suggested the presence of oils, greases, and plant-derived binders. In the low-wavenumber region, signals corresponding with inorganic fillers such as quartz, kaolin, and brick dust were observed [19], which aligned with traditional lacquer ash formulations comprising kaolin loess, tile ash, glutinous rice paste, and raw lacquer, as documented in the Record of Painting and Decoration in the chapter on texture and color [7].

The broad peak centered at 3396.03 cm⁻¹ further confirmed a high concentration of hydroxyl groups, possibly derived from plant-based fibrous materials such as flax or saccharide-rich binders like treacle [20]. The presence of carboxylate and carbonate absorption bands suggests that carbonate minerals, such as brick ash (CaCO₃), were part of the filler system [21]. The complex absorption features in the fingerprint region reflected the bending and wagging vibrations of various minerals and fibrous components, indicating that the lacquer ash layer is a hybrid structure composed of both inorganic and organic constituents [22].

3.4.2. FTIR Analysis of Surface Lacquer Layers

The infrared absorption peaks of the surface lacquer layers are presented in Figure 10.

As summarized in

Table 5. FTIR characteristic peaks and corresponding composition information of the surface lacquer layer.

Absorption Peak Position (cm−1)	Corresponding Chemical Bond/Group	Characteristics of Lacquer Ash Layer
3289.96	O–H/N–H stretching vibrations	Proteinaceous substances (e.g., animal glue)
1649.98; 1540.85	Amide I and amide II vibrations	Protein structures
2923.56; 2854.13	Aliphatic C–H stretching vibrations	Drying oil (e.g., tung oil) or natural lacquer matrix
1704.77	C=O carbonyl vibration	Quinone or ester structures (oxidative products of lacquer)
1405.85; 1319.07	Aromatic ring skeletal vibrations	Laccol polymerization products
400–580	Inorganic lattice vibrations	Inorganic red pigment Pb (Pb3O4)

, the FTIR spectra of the surface lacquer layers exhibited prominent absorption bands corresponding with O–H/N–H stretching and amide groups, suggesting the presence of proteinaceous substances in the red lacquer. These components may have been introduced as film-forming agents or to improve the lacquer’s blending properties [23]. The observed aliphatic C–H stretching and bending vibrations indicated the possible presence of natural drying oils, such as tung oil, or components inherent to raw lacquer [24].

The carbonyl (C=O) stretching vibrations were attributed to quinones and esters, typical oxidative polymerization products of urushiol in natural lacquer [22]. Additionally, characteristic absorption bands associated with aromatic ring structures confirmed the presence of polymerized phenolic compounds, constituting the lacquer layer’s principal film-forming matrix [25].

In the low-frequency region of the infrared spectrum of the varnish layer, the absorption bands observed in the range of 400–580 cm⁻¹ were primarily attributed to the bending and stretching vibrations of the Fe–O bonds in hematite (Fe₂O₂) and the bending vibrations of Pb–O bonds in red lead (Pb₃O₄) [18,26]. However, based on the combined results of the EDS and XPS analyses, Fe was not detected in the samples, thereby ruling out the presence of hematite (Fe₂O₃) as a pigment component. In contrast, Pb was consistently detected in multiple analyses, which strongly supports the presence of lead-based red pigments, particularly red lead (Pb₃O₄).

4. Discussion

This study employed analytical techniques from multiple perspectives to systematically investigate the lacquer structure and material selection of furnishings in Long’en Hall of the Qing Changling Mausoleum. These analytical methods demonstrated strong complementarity and cross-verification, which are reflected in the following aspects.

(1)

Layered Structure and Composite Material Characteristics of Lacquer Finishes on Long’en Hall Furnishings

Preliminary observations under a fluorescence stereomicroscope indicated that the lacquer structures on the furnishings from Long’en Hall generally exhibit a stratified configuration comprising a ground layer and a colored lacquer layer. A distinct gray layer of lacquer was commonly observed among the samples examined, including the offering table, incense pavilion, and poke lamp. In contrast, the throne sample did not display a similar structural feature.

This initial microscopic assessment was substantiated through a series of subsequent analytical techniques. Energy-dispersive X-ray spectroscopy (EDS) of the cross-sections from the offering table, incense pavilion, and poke lamp consistently detected mineral elements such as Ca, Si, and Al. These findings corresponded well with the absorption peaks of silicate, kaolinite, and other inorganic fillers identified in the Fourier-transform infrared (FTIR) spectroscopy analysis. Taken together, these results suggest that the ground layer likely consists of a traditional composite mixture of brick ash, glutinous rice paste, and loess. Notably, the content of these inorganic components was significantly lower in the throne sample, aligning with the macroscopic structural observations.

Regarding the colored lacquer layer, X-ray photoelectron spectroscopy (XPS) revealed the presence of elements such as Pb, S, C, N, O, and Au. These results, in conjunction with the FTIR detection of organic functional groups (e.g., C–H, C=O, and C–O) and minor inorganic vibrational peaks (e.g., Pb–O), indicate that the colored lacquer layer is composed of a hybrid organic matrix—primarily raw lacquer mixed with tung oil—combined with inorganic pigments such as red lead (Pb₃O₄) and metallic gold (Au).

The combined results from the fluorescence microscopy, EDS, FTIR, and XPS analyses confirmed that the furnishings from Long’en Hall exhibit the typical organic–inorganic composite material characteristics of traditional lacquerware. This multilayered composite structure provides strong adhesion and esthetic richness and enhances the material’s physical stability and environmental resilience. These properties ensure the long-term preservation and practical display of Qing dynasty royal ritual furniture.

(2)

Multi-Technique Cross-Validation Enhances the Scientific Rigor and Reliability of the Cultural Relics’ Protection and Imitation Technology Pathway

In this study, a combination of fluorescence microscopy, energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared (FTIR) spectroscopy was employed, demonstrating strong cross-validation and complementary functionality, with a well-defined logical sequence among the techniques. Fluorescence microscopy provided an initial assessment of the stratified structure of the lacquer layers, offering a clear direction for subsequent analyses. EDS revealed the elemental types and their spatial distribution within the cross-sections of the samples. XPS supplemented EDS by enabling the detection of trace elements in the colored lacquer layer, such as Pb and Au, which EDS alone may not effectively detect. FTIR supported these findings by identifying characteristic absorption peaks corresponding with organic and inorganic functional groups. These spectral features enabled correlations with the chemical states and compositions identified through EDS and XPS, thereby confirming the presence of relevant inorganic fillers and organic binding media.

This multi-dimensional, highly complementary analytical approach significantly enhances material characterization’s scientific rigor and reliability in cultural relic research. It also contributes to establishing a systematic structural and compositional reference framework for the technological pathway of cultural relic imitation. Such a framework can effectively inform the rational reconstruction of traditional processes—including substrate preparation, color lacquer formulation, glazing, and gilding—ultimately improving imitation artifacts’ structural integrity and decorative authenticity. This provides robust technical support for advancing the quality and fidelity of cultural relic reproductions.

(3)

Correlation Between Experimental Findings and Historical Records Reflects Process Standardization

The multi-method analytical results aligned closely with Qing dynasty historical records, underscoring the standardized and institutionalized nature of material selection and craftsmanship in royal ritual furnishings. For instance, the ash layer structure corresponded with descriptions in the Painting and Decorating Record, the materials used for the incense pavilion and offering table are consistent with those listed in sacrificial space inventories from various Qing periods, and the clay–gold overlay techniques on the lacquered throne echo details in the Craftsmen’s Regulations. These consistencies suggest that the lacquer structures and decorative techniques of imperial furniture were not the result of ad hoc craftsmanship but products of a regulated production system. The microstructural and material insights gained through modern analytical methods substantiate historical records, confirming the high degree of standardization in the material choice, structural hierarchy, and color use of Qing ritual objects.

(4)

Technical Limitations and Practical Recommendations

Although the analytical techniques employed in this study exhibited strong complementarity and collectively yielded robust results, several technical limitations remain. For instance, X-ray photoelectron spectroscopy (XPS) is restricted to probing only the outermost surface layer (approximately 5–10 nm), which is inadequate for detecting metallic decorative layers beneath a lacquer film. Energy-dispersive X-ray spectroscopy (EDS) exhibits low sensitivity to light elements such as carbon (C), nitrogen (N), and oxygen (O). Therefore, complementary techniques—such as Fourier-transform infrared (FTIR) spectroscopy, which detects functional groups through characteristic bond vibrations, and X-ray photoelectron spectroscopy (XPS), which provides the surface chemical composition—are required to obtain a more complete and accurate understanding of the material’s organic and chemical components. As such, no single technique can independently capture the full spectrum of structural, compositional, and chemical information necessary for a comprehensive material analysis.

Therefore, in future studies involving similar sample types, it is recommended that a multi-dimensional information chain encompassing structural observations, elemental analyses, functional group identification, and valence state characterization is established. This integrative strategy can provide a more systematic and reliable analytical pathway for investigating historical fabrication techniques and material compositions.

5. Conclusions

This study employed fluorescence stereomicroscopy, EDS, XPS, and FTIR to analyze lacquer layer samples collected from the surface of lacquered wooden furnishings in Long’en Hall, Qing Xiling. Initial structural observations under the stereomicroscope guided subsequent EDS and XPS analyses, which investigated the lacquer layers’ cross-sectional composition and surface constituents. The results confirmed that the furnishings predominantly feature a “gray layer–color lacquer layer” structural system. The FTIR analysis further identified the presence of natural organic film-forming substances, such as raw lacquer, tung oil, and animal glue, in the color lacquer layer, combined with inorganic pigments including minium (red lead) and metallic gold (Au). The gray layer consisted of inorganic materials such as brick ash (CaCO₃), quartz, and kaolin. These findings indicate that the lacquer system exhibits a stable organic–inorganic composite structure.

The integration of multiple analytical techniques provided complementary and cross-validating evidence, enhancing the scientific reliability of the results. These insights offer a valuable reference for future material identification and process reconstruction efforts to imitate similar historical lacquerware artifacts.