Abstract:Ancient Qigu bronze mirrors are known for their dense and smooth surface. However, due to burial and storage environments, their surfaces are often covered with corrosion products, soil, and other deposits, which compromise both their appearance and long-term preservation. Traditional cleaning methods for the surface layer of Qigu can easily cause scratches and allow chemical reagent to penetrate the surface. In this study, we investigated the corrosion characteristics of a black Qigu bronze mirror from the Tang Dynasty and, and following the principle of “minimal intervention” in cultural relic conservation, we designed and prepared a novel composite hydrogel cleaning material to clean the black Qigu bronze mirror. First, we examined the black Qigu bronze mirror and its surface attachments. X-ray fluorescence (XRF) spectrometry revealed that the mirror was made of high-tin bronze. Microscopic observation showed distinct grinding marks, dense pores, and cracks in the black Qigu regions. The corroded areas exhibited layered accumulations of hardened deposits. Scanning electron microscopy-energy dispersive spectrometry (SEM-EDS) showed that the hardened deposits consisted mainly of soil and copper corrosion products. Further analysis using X-ray diffraction (XRD) indicated that the primary components of the corrosion products were malachite and quartz.  We then conducted experiments to prepare and optimize composite hydrogel materials. Carboxylated chitosan, known for its water solubility, antibacterial properties and metal ion adsorption capacity, was cross-linked with carbomer, a thickening agent, through electrostatic interactions to form a gel carrier. Formic acid was selected as the active corrosion-removing component. By directly mixing these reactants at room temperature, we prepared a series of gel agents with different concentrations. The optimal concentration of the system was determined through viscosity test and simulated sample experiments, resulting in a white, glossy semi-solid gel cleanser with an average viscosity of approximately 82 000 mPa·s. SEM observation revealed a honeycomb-like porous structure in the gel’s microscopic morphology. Finally, the prepared composite hydrogel cleanser was applied to remove corrosion from the black Qigu bronze mirror. The mirror surface was largely covered with hardened corrosion, aged labels and other contaminants. The gel cleanser not only reacted with the corrosion but also adhered to and removed other contaminants. The procedure involved repeatedly applying the gel cleanser to the corroded areas, with each application lasting 30 min. After treatment, the gel was dried with a hair dryer, allowing it to be peeled off. Microscopic observation, ultraviolet light examination, and scanning electron microscopy confirmed that the gel cleaning effect was significant and left no residue. This research focuses on the cleaning of corrosion on Qigu bronze mirrors. Compared with previous studies , it presents two key innovations:1) addressing to the limitations of the traditional cleaning methods for Qigu bronze mirrors, it applied a hydrogel cleaning approach to the conservation and restoration of high-tin bronze artifacts, and further evaluated both the cleaning effectiveness and the potential gel residues of the cleanser, providing a valuable reference for the conservation of similar cultural relics; 2) it designed and prepared a carboxylated chitosan/carbomer composite hydrogel system specifically for the conservation of bronzes, offering a new approach for the application of the composite hydrogels in cultural relic conservation.

Abstract:Seventeen bronze mirrors from the Han and Tang Dynasties unearthed in the eastern suburb of Xi’an were analyzed using metallographic microscopy, scanning electron microscopy-energy dispersive spectrometry and Raman spectrometry to study their microscopic structures and corrosion characteristics. The results show that while the Han and Tang mirrors differed in shape and size, their main alloy compositions were similar, consisting primarily of high-tin bronze. All of the mirrors exhibited as-cast microstructures with comparable micro-morphology. The microstructure was composed of the (α+δ) eutectoid and the α phase, appearing as irregular islands and bands. Variation in cooling rates resulted in differences in the metallographic structure of bronze mirrors. All the samples displayed a stratified corrosion structure consisting of a surface corrosion layer, oxide layer, free copper deposition layer, corrosion transition layer and the underlying alloy. Lead in the bronze mirrors was the first component to corrode, and the eutectoid phase was corroded prior to the α phase. Corrosion also led to significant increase in Sn and O contents. These corrosion characteristics correspond closely with those expected from long-term burial environments. The results provide valuable references for understanding the micro-and macro-corrosion characteristics of high-tin bronzes in different environments and established a scientific basis for the preservation and restoration of bronze mirrors.

Abstract:To achieve a comprehensive understanding of the coloring techniques used on bronzes unearthed at Sanxingdui, this study focuses on newly discovered bronzes with colored decorations from the No.3, No.7 and No.8 sacrificial pits excavated during the second round of archaeological work at the Sanxingdui Site. Pigment fragments and powders that had detached and could not be reattached, as well as black substances on the bronze surface that could not be visually identified as pigments were collected and analyzed. Scientific methods—including stereo microscopy, polarized light microscopy, Raman spectrometry, scanning electron microscopy-energy dispersive spectrometry, pyrolysis gas chromatography-mass spectrometry, among others—were employed to systematically investigate the surface coloring and decorative process of 13 painted bronzes. The objective of this research is to provide comprehensive information on the pigments and technical characteristics of color application at the Sanxingdui Site. Microscopic observation, elemental analysis and organic residue testing of different samples revealed that on the painted bronzes, cinnabar was used as the red pigment, while carbon black was used as the black pigment. The cinnabar particles were relatively larger and lacked associated minerals, indicating that they were natural mineral pigments produced through grinding and cleaning, though the grinding process had not yet reached refinement achieved by the later “water flying” technique. In contrast, the carbon black pigment particles were finer, and their adhesion to the bronze surface was generally stronger. It was observed that the black patterns exhibited clear variations in shade and fineness, with visible starting points, turns, and joints of brushstrokes, as well as lines of differing thickness. Under the microscope, the strokes were evident, and the pigment layers overlapped, suggesting that the design was applied with a brush-type tool. Meanwhile, our findings indicate that the colored bronzes employed two distinct coloring techniques:filling and painting. The painting technique could be further divided into three sub-types:single-layer, double-layer and multi-layer painting. To better understand the painting process, simulated painting experiments were carried out using frosted glass sheets as carriers, focusing on paint thickness. For these experiments, cinnabar was simply ground to mimic the fragile state of the excavated artifacts. The cinnabar pigment was prepared with bone glue as a binder (ratio of glue to pigment being 1∶50) and the pigment was applied uniformly with a flat-tip brush approximately 10 mm wide. After three layers, the thickness of the cinnabar layer measured approximately 60 μm under a super depth-of-field microscope. Bronze, as a dense and extremely smooth surface, poses challenges for pigment adhesion; insufficient binder or too few layers results in pigment flow, incomplete coverage, and weak attachment. These cinnabar-decorated bronzes unearthed from the sacrificial pits of Sanxingdui feathered larger cinnabar particles, a rich color palette, and pigment layers exceeding 100 μm in thickness, indicating the use of substantial binder and multiple color applications. Furthermore, patterns were primarily created with cinnabar. In some instances, carbon black was used as the base color, with cinnabar subsequently applied thereon. Besides, for a few objects, the black pigment was applied again on the red painting to form a black-red-black three-layer painting, creating a striking contrast. The use of the finer carbon black pigment as the base ensured the particular firmness of cinnabar on the object surface. To sum up, the colored bronzes unearthed from the sacrificial pits of Sanxingdui are numerous, have a long history, and were decorated with both filling and painting techniques. The types of decoration are diverse, and the coloring processes show considerable flexibility, with patterns closely reflecting the local aesthetics and painting skills of the time. The presence of larger cinnabar particles suggests that the grinding and sieving techniques for cinnabar were still in an early stage of development. The smoothness of lines and the intricacy of the patterns rendered in carbon black depended largely on the individual aesthetic and painting abilities of the artisans, indicating that a unified and standardized production and processing system had not yet been established. This research provides important insights into the evolution of decorative techniques in ancient Chinese bronzes.

Abstract:The dozens of gold masks unearthed at the Sanxingdui Site had all suffered from severe deformation and had not been effectively protected or restored for a long time. To explore effective methods for their conservation and restoration, digital technologies such as 3D modeling, digital measurement, simulation comparison, and 3D printing were fully integrated into the restoration process. This approach not only resolved the challenge of matching the gold masks with bronze head statues to support archaeological research, but also ensured that the correction process followed the principles of “original craftsmanship” and “authenticity”. In addition, custom-made preventive support devices contributed significantly to the preservation and exhibition of the gold masks. The integration of digital technologies throughout the entire process of research, conservation and display of the gold masks has expanded new pathways for cultural heritage conservation.

Abstract:A large number of gold-inlaid gemstone artifacts were unearthed from Ming Dynasty Wangxuan Tombs in Qichun County, Hubei Province, providing important materials for the study of colored gemstones in the Ming era. In this study, nine groups of artifacts from Wangxuan Tombs in the collection of Hubei Provincial Museum were examined. The gemstones inlaid on these artifacts were identified using infrared spectrometry and X-ray fluorescence spectrometry, yielding valid data on 75 gemstones (44 red magnesia-alumina spinels, one blue magnesia-alumina spinel, 26 sapphires, and four rubies). Compositional analysis revealed that 1) some sapphires contained higher Fe mass fractions and elevated mass fraction ratios of Fe/Ti, consistent with basalt-type sapphires; 2) some red spinels had higher Ti mass fractions, resembling spinels from Myanmar. Combining these results with knowledge of Ming Dynasty trade routes and geological sources suggests that some sapphires may have originated in Thailand, while certain red spinels likely came from Myanmar. Furthermore, a comparison of the relative proportions of rubies and red spinels across tombs of different ranks, together with the distinctive inlay positions of rubies and consideration of physical property differences (e.g., density, hardness, cleavage), indicates that Ming artisans in China may have possessed the ability to distinguish rubies from red spinels. This study provides reliable data for the identification, provenance analysis, and conservation of gemstone artifacts, and offers new insights into the level of gemstone knowledge in Ming China.

Abstract:The Daxi Site, located in Daxi Village, Daxi Township, Wushan County, Chongqing, is one of the “Top 100 Archaeological Discoveries of the Century” and has yielded dozens of jade and stone artifacts with distinctive jade features of the Neolithic Daxi culture. To investigate the materials and sources of these jade and stone artifacts, 62 objects were analyzed. Surface characteristics, degree of patination, and density were preliminarily examined using conventional gemmological tools such as a 10× magnifying lens and an electronic balance. Raman spectrometry, X-ray powder diffraction, and other analytical methods were then applied for material identification. The results show that:1) conventional instrumental testing combined with spectrometric methods could effectively distinguish the materials for unearthed jade and stone artifacts—among the 62 artifacts:50 were marble, 2 serpentinite, 3 quartzite, 2 marlstone, 1 jet, 3 clamor shellfish, and 1 bone (calcium phosphate); 2) the artifacts included rings, beads, cores, pendants, stone axes, and smashed stone pieces, mainly for decorative purposes. Overall, the samples displays mixed materials and relatively lower quality—no high-quality jade and stone artifacts such as tremolite was detected. This aligns with the limited jade resources in the Daxi culture region. Comparison between the jade resources around the Three Gorges area and those from other cultural contexts suggested that marble artifacts were likely acquired locally, while materials such as jet were obtained through long-distance exchange. These findings provide new evidence for understanding jade utilization and cultural exchange in the Wushan Daxi culture.

Abstract:Flour paste is the most widely used adhesive in the mounting and restoration of painting and calligraphy relics. In this study, ultraviolet absorption spectrometry, infrared spectrometry, and scanning electron microscopy were used to analyze the effect of flour paste on mounted painting and calligraphy works, with the aim of clarifying the relationship between the paste properties and the deterioration of mounted painting and calligraphy works. The results show that:1) hydrogen bonds formed between the hydroxyl groups of starch and the fibers of Xuan paper, giving the paste both bonding and strengthening properties; 2) during deterioration, the aggregation state of starch molecules changed, the degree of internal crystalline structure ordering decreased, and the mass ratio of amylose to amylopectin first decreased and then increased; and 3) the color difference and elastic modulus of the mounted painting and calligraphy works increased, making them more prone to physical deterioration such as discoloration, creasing and fractures during long-term preservation. This study provides theoretical guidance for the scientific application and performance improvement of paste in traditional craftsmanship.

Abstract:Guanyin Temple in Changzhi preserves over 500 valuable Ming Dynasty painted sculptures. However, due to poor preservation conditions and insufficient protection, these sculptures have suffered from varying degrees of deterioration and urgently require scientific conservation and restoration. Currently, there is little systematic research focused on the craftsmanship of small suspended sculptures. In this study, fragments detached from the sculptures were selected as samples, and techniques such as X-radiography, microscopy, mineral analysis, laser particle size testing, and X-ray diffraction were employed to investigate their craftsmanship. The results indicate that the small suspended sculptures were made of finely sifted clay reinforced with bast fibers. Fine iron wires were used to support certain parts, such as the arms and drapery. The body and head were connected by a pine-wood rod at the neck. A white lime layer was applied to the surface, onto which mineral pigments—including cinnabar, realgar, atacamite, brochantite, and azurite—were painted. Finally, the sculptures were mounted on the wall using iron nails inserted into the feet. These findings provide a scientific foundation for the conservation and restoration of the suspended sculptures at Guanyin Temple.

Abstract:To preliminarily reveal the technical characteristics of bronzes unearthed from the Guangyangcheng cemetery, 61 Han Dynasty bronzes from the cemetery were examined through metallographic structural observation, elemental compositional analysis and lead isotope ratio determination. The results show that the 61 bronze artifacts exhibited two types of microstructures:casting (59) and post-casting cold working (2). Lead-tin bronze was the predominant alloy type, accounting for 96.7% of the samples, with one tin bronze and one lead-arsenic bronze also identified. Lead isotope ratio analysis revealed that 60 samples had ordinary lead, while one contained highly radioactive lead. The lead used in the Western Han bronze was derived from a wider range of sources than that used in the Eastern Han bronze. Specifically, lead materials of Class L and H, used during the Western Han Dynasty, were no longer used in the Eastern Han Dynasty. The Class H lead was closely linked to the Yan culture, and may have originated from the Yan-Liao area. In the Eastern Han Dynasty, Class B lead began to be widely adopted. The Class A, B and C leads were used in both the Western Han and Eastern Han periods, but their sources were not entirely overlapping, indicating distinct supply channels across the two periods.

Abstract:To better understand the characteristics of coffin materials during the Han Dynasties in Inner Mongolia, we conducted wood identification on 76 burial utensils from the Jihulangtu Xiongnu cemetery (dating from the late Western Han Dynasty to the Eastern Han Dynasty). The results show that the wood used were Pinus sp., Betula sp., Larix sp., and Ulmus sp., with Pinus sp.being the predominant material, accounting for 80% of the total. This preference likely reflects the composition of local vegetation. Based on the archaeological context of the samples, there was no significant difference in the choice of wood materials used for burial utensils among tombs of different ranks, suggesting that this pattern may have been shaped by the burial customs of Xiongnu, or constrained by the availability of local wood resources.

Abstract:Textile artifacts are non-renewable and vulnerable to irreversible damage caused by natural forces, making their effective conservation an urgent necessity. Based on prior damage assessment and scientific analysis, this study conducted an in-depth investigation into the design, tailoring techniques, and craftsmanship of a Qing Dynasty blue-gray python robe made of silk gauze with gold-thread embroidery, providing essential data for the development of a scientific and well-founded restoration plan. According to the principles of cultural heritage conservation and restoration, the parameters for replicating the “double-warp twisted gauze” technique were carefully determined to ensure that the replica fabric closely resembled the original. During restoration, a combined method of backing reinforcement and localized gauze overlay with needlework techniques was applied to the damaged and deteriorated areas, including the collar, horse-hoof cuffs, shoulders and hemline. This approach successfully restored the original structure of the robe, and maintained its stability and ensured its long-term preservation.

Abstract:A uniquely shaped ink ingot was unearthed from Tomb M10 of the Eastern Han Dynasty in the Dongjiang cemetery. Such cultural relics are rarely found in tombs of the same period and therefore it holds important research value. To determine its material, ultra depth-of-field microscopy, field emission scanning electron microscopy, Fourier transform infrared spectrometry, and pyrolysis gas chromatography-mass spectrometry were employed, and the results were compared with modern oil-soot ink and pine-soot ink. The findings show that the micro-appearance of the sample closely resembled that of pine-soot ink. Its FTIR spectrum showed the telescopic vibration absorption peak of the C=C bond in the aromatic ring skeleton, while its ion chromatogram revealed a series of polycyclic aromatic hydrocarbons and pyrolysis compounds characteristic of pine wood, such as retene and methyl dehydroabietate. These results confirm that the material was pine soot ink. Further observation and analysis suggest that the ink ingot was hand-molded, with a form resembled those of “garlic” and “flower” from cultural relics of the same period.

Abstract:This study examines a gilded silver-lead core lacquer dish unearthed from the tomb of Wang Jian, founding emperor of the Former Shu Kingdom (907-925 CE) during the Five Dynasties period. This artifact demonstrates both exquisite craftsmanship and a complex structural composition. Partial gilding adorns the inner wall, while the core consists of alternating layers of silver-tin alloy and lead alloy encased in lacquer. Although much of the outer lacquer coating had peeled off during excavation, visible traces remained. Analysis of the dish’s preservation state revealed notable differences between layers:the outer silver layer exhibited a smooth texture with fine grains, whereas the inner layer was rough and porous, confirming a two-layered structure. Based on this, advanced analytical methods, including super depth-of-field microscopy, scanning electron microscopy-energy dispersive spectrometry (SEM-EDS), and X-ray diffraction, were employed to comprehensively examine the morphology, structures, materials and phases of both the gilding layer and the core. Microscopic observation revealed that the inner surface of the dish was engraved with decorative patterns, then partially gilded, and subsequently modified with edge-engravings. A mercury-rich interface was identified between the gilding layer and the core, composed primarily of Au (42.42%), Ag (22.75%), and Hg (12.79%), representing a distinctive feature of gilded silverware craftsmanship. This interface was likely formed due to mercury’s high solubility in silver and thermal-induced expulsion of mercury, which facilitated inter-atomic solid diffusion.  Beneath the gilding layer, the dish contained two layers of silver-tin core, with higher contents of Ag and Hg and a small amount of Sn at the interface between the two layers. The average Hg content at the interface was 11.65%, whereas the two core layers contented 0.39% and 0.00% Hg, respectively. The silver-tin core primarily consisted of Ag₃Sn, Ag, and AgCl, while the interface was mainly composed of Ag₂Hg₃, Ag and AgCl. Based on these differences in Hg content and phase compositions, it is inferred that mercury functioned as a binder between the silver-tin alloy cores. Mercury, liquid at room temperature, can react with various metals or alloys to form amalgams. Both historical documents and foreign studies recorded the use of mercury as a binder. In this case, Hg reacted with Ag₃Sn and Ag in the core to form Ag₂Hg₃, ensuring a tight bond between the cores. This represents one of the rare publicly known physical cases using mercury as a binder, offering valuable insights into its application in ancient Chinese craftsmanship and the history of science and technology.

Abstract:The technique of Nijin has a long history and has been used in religious murals, Buddha statues, Thangkas, and related artworks. Its application of gold creates a simple, rich and textured effect, giving Buddha statues delicate and warm skin. This technique played a vital role in the production and decoration of bronze Buddha statues during the Qing Dynasty. However, among the existing bronze Buddha statues in the Palace Museum, many have suffered from serious deterioration (such as hollowing, cracking, flaking, detachment, and loss) in areas made with the technique of Nijin. To address these problems and effectively prevent further deterioration, it is essential to first identify the gold-working method and specific processes of the technique of Nijin. However, there are few historical documents describing its application to bronze Buddha statues, and no scientific analysis or discussion from a perspective of testing. In this study, to preliminarily determine the gold-working methods and the specific processes of the technique of Nijin in Qing Dynasty bronze Buddha statues from the collection of the Palace Museum, we selected five Buddha statues as the research objects. We combined scientific testing and analysis with historical records for mutual corroboration. The results could provide a theoretical foundation for future conservation treatments and technical restoration practice.

Abstract:Beishiku Temple, an important part of China’s ancient cultural heritage, has been frequently affected by erosion caused by precipitation and seepage in recent years. These forms of deterioration pose a serious threat to the safety and preservation of the site. Wind-driven rain (WDR), as a particular form of precipitation phenomenon, has inflicted significant moisture damage to the cliff faces of the grottoes. In this study, computational fluid dynamics (CFD) simulation was employed to evaluate the shielding performance of the existing temporary rain shelters against WDR and to investigate the distribution of cliff moisture under varying heights, cantilever distances, and rainfall intensities. The results provide a scientific basis for the conservation of the grottoes. An on-site investigation was conducted at Beishiku Grottoes in Qingyang, during which the necessary meteorological data were collected. The computational model was simplified to reflect the actual site situation. Prior to the simulation, a detailed analysis of the topographical features, wind speed, wind direction, and rainfall intensity of the grottoes was carried out, and appropriate boundary conditions were established. The feasibility of the simulation platform was verified through error cause analysis and comparison with actual monitoring data to ensure the reliability of the simulation results. The Eulerian-Lagrangian method combined with the discrete phase model (DPM) was applied to simulate CFD of the WDR conditions in the grotto area. During the simulation, flow field control equations for the wind and rain phases were first established, and WDR conditions under varying rainfall intensities—light rain, moderate rain, and heavy rain—were simulated through iterative solutions. The results show that the existing temporary rain shelters exert a significant shielding effect on WDR to the grottoes, significantly reducing the moisture content of the cliff face. A cantilever distance of 2 m provided an ideal shielding effect for certain areas; while cantilever distances of 3-4 m achieved a better overall shielding effect. These findings indicate that adjusting the cantilever distance of the cliff face can effectively improve the moisture conditions of the grotto cliff face, offering an important reference for the design and implementation of conservation measures. The innovation of this research lies in providing a scientific theoretical basis and design reference for conservation measures tailored to grottoes in specific climatic regions of China. Beyond its practical significance for the preservation of the Beishiku Grottoes in Qingyang, this study also offers theoretical support and reference data for the conservation of grottoes under similar climatic conditions, demonstrating important value for both academic exchange and practical application.

Abstract:To study the temporal and spatial characteristics of the meteorological environment in Cave 132 of Bingling Temple Grottoes and to explore the correlation between the cave’s deterioration and environmental changes, a study was carried out in accordance with GB/T 30237—2013 Ancient wall painting deterioration and legends and WW/T 0006—2007 Specification for condition survey of ancient murals. The distribution characteristics of deterioration in Cave 132 were examined, and air temperature and humidity monitoring data collected from January 2010 to December 2022 were analyzed. Using Origin2021 software, the average of monthly extreme values and their variation trends, and the annual frequency of days with extreme temperature and humidity events were compared. Data collected from environmental monitoring equipment placed at different heights and depths within the cave from August 1st, 2021 to August 31st, 2022 were analyzed using temperature and humidity box plots. In addition, temperature and humidity data from the surfaces of relics on both the west and east walls during the same period were compared to evaluate differences in relative humidity between mural and sculpture surfaces. The results indicate that over the past decade, the frequency of high-temperature and high-humidity events in Cave 132 has increased, with low temperatures rising rapidly. The occurrence of extreme temperature and humidity events varied from year to year, reflecting increasing environmental instability. The comparison of internal and external temperature characteristics revealed a seasonal pattern:in spring and summer, external temperatures were higher than those inside the cave, whereas in autumn and winter, the reverse was true. Temperature differences between the inside and outside of the cave were larger in spring and autumn, but smaller in winter and summer. Relative humidity inside the cave was inversely correlated with external temperature throughout the year. Regarding temporal and spatial distribution of temperature and humidity inside the cave, vertical temperature patterns generally showed higher temperatures closer to the ground. From October to March of the following year, temperature fluctuations increased from the ground upwards while from April to September, the trend was reversed. Along the depth of the cave, from October to February of the following year, air temperature gradually increased from the entrance inwards, but from March to September, it decreased. Annual temperature differences also progressively diminished from the entrance inwards. For relative humidity, vertical distribution showed lower humidity closer to the ground. Along the depth, from October to May of the following year, relative humidity decreased from the cave entrance inwards, while from June to August, the trend reversed, indicating a temporal mismatch with temperature variations. In March, April and May, rear-cave air temperatures were lower than that at the front, but relative humidity was also lower. This phenomenon is attributed to the water storage period of Liujiaxia Reservoir, when backflow toward the grottoes increased relative humidity at the cave entrance due to water vapor movement and evaporation. Vertically, relative humidity differences increased with height from October to February of the following year, while the differences decreased from March to September, mirroring temperature trends. Along the depth direction, temperature differences were generally smaller in the front than those in the rear, whereas the opposite was true for relative humidity—particularly from June to October—likely due to water evaporation from the surrounding rock. The primary forms of deterioration in Cave 132 included pigment loss, flaking, hollowing, powdering, microbial damage, with pigment loss and flaking being the most severe. In terms of distribution:pigment loss and flaking occur across all walls at similar levels, while powdering and microbial damage are concentrated in the middle and lower sections of the cave, particularly on the surface of sculptures along the west and north walls. The widespread pigment loss and flaking are likely related to both mural production techniques and environmental influences, whereas localized large-scale deterioration, such as powdering and microbial growth, appear to be closely tied to micro-environmental variations within the cave. Elevated relative humidity on the surface of relics in the rear of the cave was probably a key factor contributing to this deterioration.

Abstract:Bone relics are a key source of information in paleoanthropology and archaeology. With the integration of science and technology into archaeology, studies of bone relics have expanded from morphological to molecular levels. This shift places higher standards for conservators:beyond preserving morphological features, it is crucial to maintain chemical integrity to minimize interference with future scientific analysis. Safeguarding the authenticity of relics during cleaning and consolidation at archaeological sites is therefore critical. This review examines the potential impacts of conservation treatments on subsequent bone studies. Most cleaning methods alter bone surface and may hinder microscopic analysis. For instance, high concentrations of acetic acid and formic acid can damage microstructures. Although modifications during cleaning are unavoidable, the resulting changes can be characterized. In consolidation, carbon-based polymers may adversely affect ¹⁴C dating and stable isotopes analysis. Appropriate pretreatments can remove these polymers to obtain accurate results. However, δ¹⁸O values derived from carbonate in bone hydroxyapatite may be unpredictably altered by polymer exposure. Evaluating these adverse effects is fundamental to developing criteria for conservation practice. Future research should prioritize the influence of cleaning and consolidation on the micromorphology and chemical composition of bone relics to ensure reliable preservation and analysis.