Abstract:The Yangtze River Estuary No.2 shipwreck of the Qing Dynasty, located at the estuary of the Yangtze River, is one of the best-preserved ancient wooden shipwrecks discovered underwater in China to date. The shipwreck salvage was completed in November 2022. During the preliminary underwater archaeological investigation, the disease phenomena—especially the black contaminants in cracks and the rust-like contaminants on the glaze surface, which had a great impact on the appearance of these cultural relics—seen on some of the blue-and-white porcelains with the deformed Shou pattern from the shipwreck caught the attention of archaeologists. As the estuarine environment where the shipwreck was located is very complex and changeable, ceramics in the cargo hold may have undergone a series of changes over a time span of hundreds of years. The formation of contaminants in this process resulted from various factors in the local environment. Therefore, it is an important indication to reflect the environmental information of cultural relics in the shipwreck. In this work, three blue-and-white porcelain shards with typical contamination characteristics were selected as representative samples, and the contaminants were investigated using energy-dispersive X-ray fluorescence spectrometry (EDXRF), optical microscopy (OM), X-ray diffraction (XRD), Raman spectrometry, and scanning electron microscopy-energy dispersive spectrometry (SEM-EDS). The chemical compositions, phase components, and micromorphology of the contaminants were studied, the causes of the formation of the contaminants and the effects of the local environment were discussed, and the potential hazards were analyzed. The study show that the contaminants are mainly carbonates such as calcite and siderite, as well as iron oxides, hydroxides and sulfides. The contaminants are characterized by various interlaced phases, reflecting the complexity of the formation process of the contaminants. Even in the different positions of the same porcelain sample, reaction types and sequences may be different. Generally speaking, the process of formation of contaminants was affected by the external environment and the nature of the porcelains. The reducing environment of estuarine sediments is the main cause of the formation of siderite and metastable iron sulfides, and the contamination of the local environment by the corrosion of iron components of the ship such as nails is an important influencing factor, which also indicates the particularity of the location and underwater environment of these contaminated porcelains. The crack pattern morphology of some of the blue-and-white porcelains indicates that they (the crack patterns) were caused by physical impact, and the selective corrosion of wollastonite crystals in the glaze led to the formation of corrosion pits. Both cracks and pits provided channels for external contaminants to enter the glaze, leading to the degradation of the porcelain. The environmental changes may cause the iron sulfides in the glaze cracks to undergo oxidation transformation and thereby volume change after the shipwreck was raised from underwater. These changes may exert pressure on the cracks or pores, resulting in further breakage of the glaze. Therefore, it is necessary to pay attention to this potential hazard. To sum up, the scientific studies on the contaminants in the blue-and-white porcelains are helpful in understanding the burial environment and preservation status of the cultural relics in the Yangtze River Estuary No. 2 shipwreck, and could also provide a scientific basis for the follow-up conservation of the ceramic cultural relics.

Abstract:Painted enamel is a kind of craft introduced from European countries during the Qing Dynasty. The study of the development of painted enamel glaze is of great significance for understanding the evolution of painted enamel craft and the technological innovation of famille rose crafts affected by it later. The gold-red glaze was at first imported from the West. This gorgeous pink made using gold as a raw material has unique significance in the development of Chinese over-glaze ceramics. However, it is difficult to effectively analyze the composition of gold-red using conventional non-destructive methods, leading to the research on gold-red mainly focusing on literature analysis. To study the painted enamel collections in the Palace Museum, an electron microscope equipped with a low-vacuum module was used to directly observe the morphology and distribution of the gold nano-particles in the gold-red glaze. Using energy spectral analysis, previous literature research on the existence of gold-red made according to the foreign “Cassius Purple” formula and the Chinese local formula “copper-blended gold-red” was verified. At the same time, a previously unnoticed gold-red formula in China was discovered, in which the element of arsenic was used as a reducing agent to prepare gold-red glaze.

Abstract:A large number of Han Dynasty bronzes unearthed in Guangzhou have brought about many achievements in their archaeology, but there are fewer studies of their provenances using archaeometric methods. In this study, the compositions and lead isotope ratios of the Western Han Dynasty bronzes unearthed in Guangzhou were analyzed and then compared with those of bronzes from the same period unearthed in Guangxi, Jiangxi, Yunnan, Guizhou, Anhui, Hubei, Henan, Hebei and Beijing. According to their remarkable characteristics of being arsenic-containing, it was believed that they might share the same mineral source with the bronzes from the same period unearthed in Hepu, Guangxi. The lead isotope ratios tested were highly concentrated, indicating the mineral should come from the same place. Through the comparison of lead isotope ratios of bronzes from the Warring States Period to the Western Han Dynasty in Guangdong, Guizhou, Yunnan, Shaanxi and Henan, it was found that the bronzes unearthed in Guangdong, Guizhou and Yunnan belonged to a large ore-forming area, obviously different from those unearthed in Henan and Shaanxi, etc. It was verified that the Western Han Dynasty bronzes unearthed in the Lingnan region were native to local places.

Abstract:Shizhaishan tombs are indigenous to the Dianchi region of the Han Dynasties. In order to understand the production process of Han Dynasty copper artifacts in Kunming, Yunnan Province, we used metallographic microscopy, scanning electron microscopy-energy dispersive spectrometry to study 31 bronzes from six tomb groups:M3, M5, M6, M7, M10 and M12. The results show that 30 objects are copper-tin alloys and that one is red copper, and all of them were cast, with only the blade of a copper Ge undergoing hot forging processing. The analysis results enrich the study of copper artifacts of the Shizhaishan culture, provide a scientific basis for the conservation and restoration of artifacts, and also supplement some information for copper archaeology and metal technology history of Yunnan in the Han Dynasties.

Abstract:We investigated the Asian lacquer-based surface coating of a historical Guqin named “Qiu Bo” collected in the Museum of Dr.Sun Yat-sen in Zhongshan, Guangdong Province, China. The instrument is believed to have been made in the studio of Prince Yi of the Ming Dynasty in Fuzhou, Jiangxi Province, and has been widely deemed as one of the four most treasured Guqin pieces in the Lingnan region. Multi-analytical measures, including optical cross-section microscopy, SEM-EDS, micro-Raman, O-PTIR and THM-Py-GC/MS, were used to identify the inorganic and organic materials for the surface coating and to reconstruct its lacquering techniques. The analytical results reveal two generations of layers with distinct materials and crafts. In the earlier generation, the ground layers were made of inorganic minerals and protein-non/semi-dyring oil binding media. In the later generation, the ground layers were made of deer antler or bone ashes bound with Asian lacquer-drying oil. These findings correspond to the instrument’s inscriptions indicating its fabrication in the Ming Dynasty in 1636 and its restoration in the Qing Dynasty in 1864. Laccol, a lacquer species, was discovered in the restoration layers using the ESCAPE database and the Excel worksheet developed by Getty Conservation Institute. This is the first reported case of laccol, primarily produced in Vietnam, used in Chinese domestic Guqin instruments. By combining scientific analyses and archival research on historical Guqin and lacquer art treatises such as Tai Gu Yi Yin, Xiu Shi Lu, etc., this study contributes to a better understanding of the craft for making the Guqin and the restoration traditions in pre-modern Guangdong. This knowledge could also benefit the conservation treatments of Guqin and other lacquer artworks.

Abstract:Our country boasts an extensive collection of stone monuments. Employing traditional techniques for rubbings on these artifacts allows for the limitless replication of their inscribed content, serving both dissemination and preservation purposes. However, improper handling during the rubbing process can lead to ink contamination on the surface of these relics. A prevalent issue is that a significant number of stone monuments in China are dense ink layers that obscure their original appearance, rendering it challenging to discern the pre-existing characters and patterns on stone surfaces. The main approach to the removal of ink contamination on the surfaces of stone monuments is conventional physical cleaning methods. These methods lack the requisite specificity to selectively target the inky residues. Comprising solid carbon black particulates mixed with animal glue and water, the ink is subjected to pounding repeatedly before becoming dry. Subsequently, the ink adhered to the stone surface using animal glue as an adhesive forms indelible traces that are difficult to remove. This animal glue is predominantly constituted by proteins. By disrupting the protein within the animal glue, its adhesive properties are lost, and thus the ink will lose its ability to adhere to the stone surface. To verify this concept, our study compared the property of protein enzymes to hydrolyze the main protein component of animal glue, investigating the efficacy of bio-cleaning agents formulated from different protein enzymes and comparing them with conventional physical cleaning methods. The effectiveness of various cleaning materials was assessed through comparative analyses of photographs, microscopic images and chromatism before and after cleaning. Experimental results demonstrate that enzyme cleaning agents formulated with surfactants exhibited more noticeable ink removal effects compared to deionized water and ethanol. Among enzyme materials, a 1% alkaline protease solution achieved the best ink removal results. Formulating enzyme materials with sodium dodecyl sulfate (SDS) and aliphatic alcohol polyethylene ether (AEO₉), experiments indicate that the best cleaning performance was achieved when alkaline protease was combined with AEO₉. Incorporating liquid cleaning agents on vertically oriented stone monuments leads to fluidity issues and contaminates the experimental area. To enhance adhesion, gel materials were employed. Various gel materials were tested, and the gel produced using enzyme agents in conjunction with Carbopol 940 exhibited the best adhesion performance on stone monuments. This improves contact between the cleaning material and the artifact surface, significantly enhancing cleaning efficacy. This gel-based approach is suitable for carrying cleaning agents applied to stone monuments. Two on-site experiments were conducted on the surface of inscriptions within the “Inkstone Studio Reviews” collection at Xi’an Beilin Museum. Deionized water, ethanol, liquid enzyme materials, surfactants and cleaning gels were employed for these experiments. The experiments reveal that the cleaning gel produced using AEO₉ and Carbopol 940 exhibited superior cleaning effectiveness compared to other liquid cleaning materials. Moreover, this gel could even effectively clean ink traces in crevices on the surface of stone monuments without affecting the artifacts themselves.

Abstract:The surface strength of rammed earthen sites is an important testing index and a basis for evaluation of the reinforcement effect. Restricted by factors such as sampling and transportation, the conventional strength test method is not applicable to the effect evaluation of measures like rammed earth filling and surface reinforcement. Since the penetration resistance method is a common mortar strength testing method, the mortar penetrometer was modified to reduce the measuring range. Sampling and indoor experiments were conducted, proving high accuracy of penetration depth values, and finding the power function relationship between the measured penetration depth and the compressive strength of rammed earth samples. In the in-situ tests, influences of point density on the accuracy of measurement results were analyzed, and the average compressive strength of the tested area was calculated using the strength measurement curve. This research proposes a set of testing methods combining instrument modification, indoor calibration and in-situ multi-point measurement, which is suitable for evaluating the surface strength of rammed earth sites. It provides a reference for the construction of an evaluation system for the reinforcement effect of rammed earthen sites.

Abstract:The writing on the surface of artifacts provides key information for understanding history, and the exploration of it becomes an important part of artifact conservation. Combining manifold learning and spectral unmixing, we propose a new method to enhance the writing on the surface of artifacts. Firstly, isometric feature mapping based on manifold learning was used to reduce the nonlinear dimension of the preprocessed hyperspectral images, and a gray image with the most abundant information was obtained. Secondly, the spectral characteristics of text and background were analyzed, and the multilayer nonnegative matrix decomposition method was used to obtain the handwriting abundance map. Then the gray image and the abundance map of the handwriting were weighted together to obtain the handwriting enhancement image; the handwriting fusion image was obtained by HSV fusion of the handwriting enhancement image and true color image. Finally, in order to better identify the text, it was cropped on the handwriting enhancement image and morphological transformation was performed to obtain the handwriting extraction map. The hyperspectral image of a faded text in Cave 38 of Yungang Grottoes was taken as an example, the results showing that the proposed method could effectively enhance the text on the surface of cultural relics and its effect was better than those of other enhancement methods.

Abstract:Mechanical properties provide essential information for assessment of preservation in waterlogged archaeological wood, as well as for the core task of reinforcement and enhancement in conservation work. However, being limited by the amount and dimensions of samples, the mechanical characterization of waterlogged archaeological wood has long been challenging. Thus, there is an urgent need to develop new technologies for testing mechanical strength of waterlogged archaeological wood in a non-destructive and accurate way. This study proposed, for the first time, the use of a thermomechanical analyzer (TMA) as a new method for testing the flexural strength of waterlogged archaeological wood. Its applicability was investigated with the shipboard (Pinus sp.) of the NanhaiⅠshipwreck as the study object. In this study, 32 waterlogged archaeological wood specimens, with the dimension of 8 mm × 2 mm × 0.3 mm, were taken and tested, and 31 valid flexural strength measurements above the 95% confidence level were obtained. The results show that the fracture strain of waterlogged archaeological wood was concentrated between 0.5% and 1.75% and the average flexural strength was only 5.64 MPa, which was significantly lower than the value of 30 MPa seen for the healthy pine wood. In addition, it was found that the strength of samples with a higher percentage of latewood was generally higher than that of earlywood samples. This study illustrates that the use of the TMA can effectively measure the mechanical properties of fragile and waterlogged archaeological wood of very low strength, and requires millimeter-level samples. TMA measurements boast high testing accuracy and good data repeatability, and provide a new non-destructive and accurate testing method that effectively complements the existing mechanical testing methods for fragile archaeological wood in terms of tiny sizes, and has good applicability and application prospects.

Abstract:Light-transmissive photography, evolving from conventional visible-light photography, is a non-destructive photographic inspection method developed for ancient Chinese calligraphy and paintings and other cultural relics which can be transmitted by visible light. It is found through practice that light-transmissive photography has many functions in the field of restoration and research on ancient calligraphy and paintings:to observe the stitching of the first lining and the backing of calligraphy and paintings and other mounting conditions; to discover previous reinforcement, mending and infilling and other restoration traces; to acquire the underdrawing content of paintings; to enhance the visual effects of damage for its analyses. Light-transmissive photography could provide intuitive and reliable deep visual information and assist restorers to understand the internal states of cultural relics, playing an important role in the restoration and research on ancient calligraphy and paintings.

Abstract:The overall layout of Xiange Tai (also known as Jueliang Ci) is symmetrical from the east to the west on the central axis, and the existing buildings are regulated as a three-entry courtyard, with the main gate, the halberd gate, Dacheng Hall, and Xiange Study Hall in turn from the south to the north. Dacheng Hall, as the most central building of Xiange Tai, boasting a magnificent appearance and beautiful colored drawings, has a width of seven rooms and a depth of five rooms, and is a single-eaved hiatus style building. Green glazed tiles covering the roof, corridors around and 24 square pillars of green stone supporting are the distinctive features of Dacheng Hall, which is unique among the Confucius Temples in China. Under the long-term influence of the natural environment and human factors, the painted surface of Dacheng Hall has suffered from a series of diseases such as color fading, cracking, pigment falling off, etc. The painting restoration work has become a prominent problem that needs to be solved for the current conservation of the cultural relics. We analyzed the layers and forms of the painted samples in detail, and conducted a comprehensive study from multiple angles, including the profile and surface, to find that 1) most of the painted samples consisted of the base layer, plaster layer and pigment layer in sequence from the inside out; 2) the plaster layer of the blue samples was made via the traditional single-layer plastering process; 3) the red samples had no plaster layer—the red pigment was painted directly on the base layer. It is speculated that this may have something to do with the development of the times and the changes in the craftsmanship. In order to better serve the scientific conservation of the cultural relics, it is necessary to understand the pigment composition and production process of color paintings of Dacheng Hall. In this study, modern technologies and methods such as super depth-of-field 3D microscopy, scanning electron microscopy-energy dispersive spectrometry and Raman spectrometry were used to analyze the layer structures, microscopic forms and compositions of the pigment samples. According to the profile observation results, the pigment layer of Dacheng Hall had more than two sub-layers, indicating that it had been repainted in history. Besides repainting, we also found the painting process of using one pigment (as the surface) covering another pigment (as the base). In terms of pigment materials, the red one was hematite, the blue ones were natural ultramarine and synthetic ultramarine and modern pigments were used for parts of the paintings. The plaster layer was mainly made via the calcite-based single-layer plastering process. In addition, it was also found that the thickness of the pigment layer of the painted samples varied from one another, and that falling off to different degrees appeared on some pigment surfaces. Therefore, the repair materials, cleaning and reinforcement methods used in the subsequent restoration need to be further studied. The results of the study provide key information for the identification of pigments and the selection of repair materials for Dacheng Hall and provide a scientific basis for the following conservation of painted cultural relics, avoiding problems such as “protective damages”.

Abstract:The gas pollutant SO₂ is one of the important factors causing the deterioration of cultural relics in Yungang Grottoes. In order to clarify the deterioration of Yungang sandstone in the presence of SO₂ and moisture, indoor simulated weathering tests under different SO₂ concentrations, relative humidity and precipitation conditions were carried out to measure the mass, surface characteristics and chemical composition changes of samples. The results show that 1) SO₂ easily reacts with carbonate minerals (such as calcite) and feldspar in sandstone, giving rise to products including CaSO₄·2H₂O, MgSO₄·7H₂O and kaolinite, etc., and that with an increase of relative humidity, the degree of reaction increases, resulting in an increase of sample mass, color difference, soluble salt content and a decrease of the Si/Al ratio; 2) the participation of liquid water can accelerate the interaction between SO₂ and sandstone significantly, which not only increases the variation range of various indexes, but also increases the invasion depth of SO₂. These research results could provide a reference for scientific understanding and preventive conservation of sandstone cultural relics.

Abstract:Microorganisms are ubiquitous on cultural heritage objects and historical architectures. Unfortunately, physical and chemical methods are relatively limited in terms of efficient prevention or removal of microbial damage for heritage items in that the available methods are generally inadequate to clean and prevent recolonization on open-air cultural heritage objects. In the field of cultural heritage conservation, the use of antimicrobial nano-materials has gradually become a new and environmentally friendly technology. This paper summarizes the current situation and developmental trends of research on the prevention and control of biodeterioration of cultural heritage objects, reviews the application of chemical biocides, natural antimicrobial agents, essential oil fumigants and new antimicrobial nano-materials in the conservation of cultural relics, analyzes the differences and mechanisms in the effects of various biocides on targeted cultural relics, and lists the potential for application and existing deficiencies of different nano-materials. This paper would not only provide a valuable reference for the management of microbial deterioration in the conservation and restoration of cultural relics, but also promote the research and development of microbial control materials and their application technologies for cultural heritage conservation.

Abstract:Complicated circulating, cutting, repairing and remounting are common situations seen for ancient Chinese calligraphy and paintings. Because of these, a lot of historical information, having been folded, stacked or covered, is unable to be acquired via naked eye observation. The damages to paper, silk, ink marks, pigments and seal impressions in calligraphy and paintings also lead to many questions. In recent years, the hyperspectral technology, as a non-invasive spectral imaging technology, has been gradually applied to colored cultural relics. This technology can provide richer information for the research and conservation of ancient Chinese calligraphy and paintings. Based on literature research, this paper briefly introduces the principle and technological characteristics of hyperspectral imaging and summarizes its practices in the studies of ancient Chinese calligraphy and paintings. In addition, domestic and foreign research using the hyperspectral technology on calligraphy and paintings, archives and relevant colored cultural relics, especially in terms of visual enhancement, material identification and virtual restoration, were sorted out, in an attempt to provide references for domestic conservation work in the future.

Abstract:Daiwang Fu (Mansion of Prince Dai) belongs to the provincial cultural relic protection units of Jiangsu. It has color paintings (without the ground layer) drawn in the late Qing Dynasty, but as time goes by, they have suffered from many kinds of diseases, including surface powdering, paint layer cracking, shedding and mold breeding, etc. Through on-site investigations and detections, the design scheme of first-aid conservation and restoration was made for the color paintings. According to the scheme, the conservation and restoration of Daiwang Fu paintings were carried out, and expected results were achieved. The protection technology could provide a reference for the conservation of the same type of ancient architectural color paintings.

Abstract:Due to the instability of the artificial-natural complex ecosystems and the complexity of the preservation environment, rock-soil relics have long been threatened by biotic and abiotic factors. The effects of plants on heritage sites and their protection applications have always attracted much attention. In the summary of relevant research results, it is found that the new on-site protection technology based on plants has advantages such as going green, sustainability and environmental compatibility, environmental protection and easy implementation, and has gradually become an alternative to engineering rescue protection measures for the protection of rammed earth sites. However, the mechanisms of the effects of plants on rock-soil relics are still insufficiently understood and the research technology is limited, with the result that the applications of new technologies of prevention and control lag behind, giving unsatisfactory results. Thus the selection of plant species and their subsequent maintenance on site are difficult, which have made unclear the dialectical relationship between plants and rock-soil relics. In combination with the biological problems faced by cave temples and earthen sites, and in view of the limiting factors for the application of plant protection technologies for sites in arid areas of China, the following perspectives are considered:1) clarification of the damage and protection mechanisms of plants for rock-soil cultural relics; 2) establishment of a scientific evaluation system to define the positive and negative effects of plants on geotechnical relics in different environments; 3) definition of the interaction between plants within and between species and the key factors driving plants to build on the surface of geotechnical relics; 4) combination of global climate changes to research and develop precise prevention and control technologies for plants harmful to rock and soil cultural relics; 5) screening suitable soft cover plant species and evaluating their protective effects and 6) development of soft capping technology based on BSC, and carrying out assessments of environmental adaptability and protective effects.