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This work proposes the virtual restoration of the Bodhidharma polychrome sculpture from the Lingyan Temple in China. Based on scientific analyses and simulation experiments, exterior colours and textures were virtually restored by combining 3D scanning and multi-view 3D reconstruction. At the same time, an efficient cultural relics high-fidelity information 3D modelling method was proposed. Colours and textures are essential for polychrome cultural relics, reflecting the historical appearance and technology. Due to long periods of natural ageing and the destruction of environmental factors, the colours and textures of polychrome sculptures are often altered or radically changed, making it difficult for people to appreciate the initial appearance. With the rapid development of digital technology and high-fidelity 3D modelling, virtual reality technology allows us to restore the appearance of cultural relics. This study expands the dimension of cultural relics exhibition, provides new perspectives for archaeology, art history and cultural heritage research, and provides a reference for the virtual restoration and digitalised archive of other cultural relics.

Nanhai I shipwreck was a large wooden merchant ship (22.15 m in length and 9.85 m in width) built in the Southern Song Dynasty (1127–1279 A.D.) of China, which was heavily loaded with a large number of porcelain and iron artifacts. In the South China Sea, it was found in 1987 and lifted as a whole in 2007. Its excavation provides a precious opportunity to reveal the preservation status of Nanhai I shipwreck. Iron compounds give rise to challenges in conservation procedures and the long-term stability of Nanhai I shipwreck. In this paper, the degradation of the wood and the iron deposits in the wood structure are investigated from the aspects of microscopic morphology, composition, and distribution to evaluate the preservation state of the waterlogged wood. Physical parameters, chemical composition, and the results of elemental analysis, and FTIR analysis suggest that the cellulose of wood is degraded, and the relative concentration of lignin increases. The ash content varies greatly among different samples, and the element of the highest content in ash is iron. The study on transverse and longitudinal sections from samples indicate that the deposits are unevenly concentrated in the cell lumen, middle lamella, rays, and pits of the cell wall. The cell lumen is filled with deposits in areas close to the surface of the samples. The XRD analysis demonstrates that the deposits in wood are mainly iron deposits, containing compounds pyrite (FeS2), siderite (FeCO3), iron oxyhydroxides (FeOOH), and magnetite (Fe3O4). The micro-X-ray Fluorescence mapping analysis suggests that the content of iron is relatively richer while containing less sulfur on the exterior of the sample. The presence of iron deposits accelerates wood degradation and increases the safety hazards of shipwrecks in the preservation process. We hope that our findings can make a modest contribution to iron removal from waterlogged archeological wood and shipwreck conservation.

Scientific analysis revealed the materials and techniques used in the process of making polychrome sculptures providing a solid foundation for the protection and restoration of the painted statues. In addition, the analyses revealed changes in colour schemes applied to the sculptures can provide the basis for the virtual restoration of the painted statues. In order to carry out scientifically-informed protection and restoration of the Bodhidharma statue from the Lingyan Temple, Changqinq, Shandong, several analytical methods such as optical microscope (OM), Micro-Raman spectroscopy (μ-RS), scanning electron microscopy coupled with energy dispersive X-ray analysis (SEM–EDS) and Fourier transform infrared spectroscopy (FTIR) were employed. Analyses clearly reveal the information including the stratigraphic structure and the composition of pigment. The use of silver foils and golden yellow pyrophyllite mineral to replace gold foils were found in the gilding paint layer in the later repainting after the Song Dynasty. This work reports the coexistence of emerald green (Cu(C2H3O2)2·3Cu(AsO2)2) and the degradation product lavendulan (NaCaCu5(AsO4)4Cl·5H2O) in large areas of the paint stratigraphy and on the surface confirming that the degradation of emerald green is related to the thickness of the paint layer; in thinner paint layers emerald green is transformed in lavendulan, while thicker layers of contain both lavendulan and emerald green, suggesting an environmental source of chlorides.

As non-renewable cultural heritage, wall paintings play an important role in society. To reveal the trends in the scientific analysis of mural paintings, 845 relevant research articles published from 2011 to 2021 were collected from the Web of Science database and analyzed. The VOSviewer software was adopted to map the network data of scientific publications, so that relationships among authors, countries, institutions can be displayed, and the co-occurrence of keywords and co-citation can be analyzed. The results revealed close and strong interconnections between the top authors, suggesting a considerable strong research link in this field. The cooperation between research institutions was relatively close. The most productive country of relevant publications was Italy. The leading journals for the scientific analysis of wall paintings were Journal of Raman Spectroscopy and Journal of Cultural Heritage. At present, the hotspots of scientific analysis and research on wall painting are revealing the composition, distribution, origin, and deterioration mechanism of pigments, alongside with evaluating the effects and mechanism of conservation materials and techniques. On the one hand, a possible development direction in this field is introducing more cutting-edge analysis and data processing methods. On the other hand, scientific analysis is increasingly adopted to guide the research and development of mural conservation materials. Introduction Methodology Results and discussion - Analysis of publications - Article network analysis -- Analysis of author cooperation relationship -- Analysis of country cooperation -- Institutional analysis -- Journal analysis -- Keyword co‑occurrence and keyword cluster analysis - Analysis of frequently cited literature

For conservation and restoration purposes, the precious historical rubbings preserved in Wuyuan Museum were studied by multi-analytical techniques including 14C radiocarbon dating, scanning electron microscopy (SEM), Pyrolysis–Gas Chromatography/Mass Spectrometry (Py-GC/MS) and Herzberg staining method. The results showed that the Py-GC/MS method is an efficient method for identifying the raw materials of paper and ink in historical rubbings simultaneously. Through Py-GC/MS analysis, five types of constituents could be detected: (1) polycyclic aromatic hydrocarbons (PAHs) from soot; (2) compounds related to tar of conifer wood: retene and methyl dehydroabietate; (3) marker compounds from the whole egg; (4) additive compounds: menthol and curcumene, which were found for the first time in ink; (5) biochemical compounds from bark paper: β-amyrin and α-amyrin. Based on the above results, the ink type, binding media and additives in ink, as well as the fiber origin of the rubbing paper could be concluded. This study could not only provide scientific support for conservation and restoration of the historical rubbings preserved in Wuyuan museum, but also give method guidance for analysis of the uncharacterized rubbings from different origins.

Samples of northern porcelain wares dating to between the 6th and 13th centuries from the three most important northern Chinese ceramic kiln sites, Gongyi, Xing and Ding have been studied in this work. The Sr isotope and chemical compositions of the ceramic glazes of these wares have been determined. Based on the scientific results we have been able to suggest the raw materials used to make the glazes. Using Strontium isotopic analysis we have successfully shown that the earliest use of limestone as a glaze flux so far identified is during the period from the Sui to mid-Tang Dynasties (late 6th-early 9th century) to produce white slip glazed ware in the Xing kilns so it may have been ‘invented’ there.

Man-made ancient Chinese barium copper silicate pigments: Chinese (Han) Purple, BaCuSi2O6; Chinese (Han) Blue, BaCuSi4O10; Chinese Dark Blue, BaCu2Si2O7(in summary called Chinese blues), and platelet-like crystals of BaSnSi3O9were detected on mural paintings of a tomb in Luoyang City, Henan Province, China, dated to Western Han Dynasty (206 BC–8 AD). The pigments of the LY01 and LY02 samples were analyzed by archaeometrical methods: powder X-ray diffractometry (XRD), scanning electron microscopy (SEM–EDX) and micro-Raman spectroscopy. While the artificial nature of the ancient barium copper silicates was undoubted, the synthetic or mineral origin of BaSnSi3O9of these murals had to be clarified. Involvement of the rare mineral pabstite Ba(Sn,Ti,Zr)Si3O9from the Tian Shan mountains could be ruled out due to absence of Ti and Zr in the elemental composition. Tin compounds as admixtures to the lead minerals—the latter required as flux additive for the preparation of the Chinese blues—or tin admixtures to pristine barium starting minerals could be excluded, as well as the use of tin containing mineral mushistonite (CuSn(OH)6), primarily intended to be applied as copper source. Related to the findings for the production of Egyptian Blue (CaCuSi4O10), bronze or bronze scrap including also corroded material was used intending copper recycling. For the synthesis of the Luoyang Chinese blues only low amounts of bronze or bronze scrap were required providing the additional advantage to form in presence of air a tin/lead oxide flux with lowered vitrification temperatures and viscosities. This marked the advent of an ‘innovative production technology’ avoiding addition of large amounts of lead minerals as an effective lead-only flux. Despite of the chemical similarity to production of Egyptian Blue, the tin/lead based developments for the Chinese blues were anticipated to be independent excluding technology transfer from ancient Egypt. For further substantiation of the appearance of pabstite in the Luoyang Chinese blues a contemporary independent synthesis was sought, carried out under conditions similar to those of the barium copper silicate syntheses (1000 °C, but absence of a flux) starting from cassiterite (SnO2), quartz (SiO2) and witherite (BaCO3).

Red discolorations are an effloresce phenomenon detect on the surface of stone objects and considered as damage factor in both esthetic and conservation points of view. It is very difficult to remove and seldom report about their weathering mechanism. Recently, numerous of red discolorations have affected the limestone objects of Lingyan Temple in Shandong province, one of the most important building materials in China. In order to set up the appropriate conservation remedy, it is essential to identify the origin, characteristics, composition, and the formation process of red discolorations. Several analytical and investigation techniques, such as X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), Micro-Raman spectroscopy (Raman), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) equipped with energy dispersive spectrometer (EDS) were used to better understand the red discolorations. The results demonstrated that the discolorations on limestone surface have been caused by carbonic acid weathering process. The red discolorations consisted mainly of kutnohorite (Ca(Fe,Mg,Mn)CO3) and iron oxides. They showed tabular, lamellar, and granular morphologies, which originated from the in situ carbonic acid weathering of kutnohorite. After rainfall, the Ca, Mg, Mn ions with relatively high solubility were primarily leached from carbonatite phases. It was resulting in the sedimentation of red iron oxides through a chemical reaction and physical adhesion. Based on those analyses, a chelating agent (ethylenediamine tetraacetic acid disodium salt) was chosen to remove theses red discolorations on the stone object.

The spontaneous degradation of pigments in painting may occur depending on environment, especially the surrounding condition of high humidity and soluble salts. Even some of these are well studied, more investigations are still in need for heritage science. Paint cross sections from Vairocana Statue in Dazu Rock Carvings, one of World Cultural Heritage, Chongqing, China are studied by optical microscopy (OM), Raman spectroscopy (Raman) and mapping, and scanning electron microscopy coupled with energy dispersive X-ray analysis (SEM–EDS). Ultramarine blue, emerald green, synthetic atacamite, vermilion, red lead, gold foil, orpiment, cerussite, gypsum and barite are identified as pigments. Moreover, lavendulan (NaCaCu5(AsO4)4Cl·5H2O) and mimetite (Pb5(AsO4)3Cl) are degradation products of emerald green (Cu(C2H3O2)2·3Cu(AsO2)2) and cerussite(PbCO3) originally used as green pigment with mixture. These secondary products is formed via multistep progresses as degradation of emerald green and cerussite, oxidation of arsenite ((AsO2)-), migration of arsenate ((AsO4)3-) and precipitation reaction of these ions with other necessary ions from environmental conditions. Based on the pigment and paint layer stratigraphy analysis, the paintings of the statue have been executed at least four times and the most recent may be after 1850s. The formation of lavendulan give rise to a highlight for identification of green copper-arsenic containing pigments and characterization of degradation in complex conditions.

The difference in the chemical compositions between Neolithic pottery from the eastern and western ends of the northern Chinese Loess Plateau has been known for some time, and a number of possible explanations have been proposed. However, a full understanding of the difference is yet to be achieved. Based on recent geological studies of the Tianshui‐Qin'an area on the western Loess Plateau, the present study establishes a logical connection between the chemical characteristics of Neolithic pottery from the western Loess Plateau and the primary sediments available in the area. Moreover, this study reveals that the chemical compositions of clay used for fine wares and coarse wares at Dadiwan also bear some clear differences. Based on these findings, the paper discusses possible clay selection methods by potters in the Neolithic western Loess Plateau to make their different wares based on the locales where suitable raw materials are available. The paper demonstrates that the raw materials available for pottery making on the eastern and western Loess Plateau differ significantly and this explains the marked difference in ceramic composition between the two locations.

Compared with other wall paintings, tomb murals are rarely and have been most seriously damaged by natural weathering, erosion of bacteria and vandalism. Traditional identification methods are time-consuming, laborious, and confined to the visible light range, which mainly relies on expert's experience, analogy and visual color. This calls for new recording methods for mural site protection, relics restoration and repairs. Hyperspectral imaging can capture pictures of spectral range from visible to near infrared light, which render visual enhancement of faded tomb murals. This paper presents a method that can extract faded mural pattern from the hyperspectral images of mural, taking the leaf-like mural patterns in typical Tang dynasty tomb in China as an example. In the method, the faded leaf-like patterns are highlighted through normalization of sensitive spectral bands and extracted by density slice and masking on image space. The result shows that the method can extract the target pattern efficiently with the simple operations.

The effect of three kinds of lead additives on Chinese Purple synthesis was studied in this research. The barium source of the Chinese Purple was barium carbonate (BaCO3), and three common lead additives in the ancient samples, lead oxide (PbO), lead sulfide (PbS) and lead carbonate (PbCO3), were used in this study. The microstructures of the three additives were observed by SEM, and the thermal analyses of three formulation powders were conducted by TG. After the reaction, compositions and chrominance of the pigments were measured by XRD and colorimeter, respectively. It is shown that PbCO3 could decrease the synthesis reaction temperature effectively, thus the pigment synthesis reaction could occur under the low temperature (720 °C–900 °C), and a brighter, purer Chinese Purple pigment could be obtained.

Ancient Chinese objects dating from the Warring States period (475–221BC) to the Han dynasty (206BC–220AD), including faience beads, wall paintings, polychrome decoration on pottery, stone and bronze objects, were studied using Raman microscopy and polarized light microscopy (PLM). Chinese Blue (BaCuSi 4 O 10 ) and Chinese Purple (BaCuSi 2 O 6 ) were identified, and additionally dark blue particles of a new pigment BaCu 2 Si 2 O 7 were also detected in purple decoration. Based on PLM observation, Chinese Blue, Chinese Purple and BaCu 2 Si 2 O 7 frequently coexist in single polychrome samples and cannot be individually identified using other analytical methods because of the minute amount that these chemicals present: sometimes comprising just one or two particles. The use of Raman spectroscopy can identify such small presences. This paper illustrates the man-made barium copper silicate pigments along the Qin historical development and shows the advantage of PLM combined with Raman spectroscopy to analyses pigments giving us an overall picture of the dates and the places where barium copper silicate pigments were used in ancient China. Their origin, decline and manufacturing techniques are also discussed.

A royal tomb of early period of the Western Han dynasty (206 B.C–8 A.D) was excavated by archaeologists in Qingzhou County, Shandong Province in 2006. Over 2000 polychromy terracotta soldiers, horses, chariots, servants etc. were unearthed from the tomb. All the terracotta figures are one quarter or one sixth as large as the livings, most of them were painted with well designed patterns. In order to gain complete information about the materials and techniques used for the polychromy on the terracotta army, five samples from the painted areas were taken. In addition, one sample from the area to adhere one leg to the ploychromy horse body was also obtained. The analytical techniques applied include XRF, FTIR, Py-GC/MS and GC/MS. Chinese purple, cinnabar, lead red and ochre were used as pigments, while animal glue was identified as binding medium and adhesive in the polychromy terracotta army in the Han Dynasty. The results definitely will provide new evidence about the materials and technologies used in Han Dynasty. Especially, the binding medium identified is different in comparison with Qin Shihuang's terracotta army (259–210 BC).

Knowledge about pigments applied in ancient wall paintings is of great importance in art conservation and art history. In this study, fifteen pigment samples from the wall painting on the pilgrimage-corridor at the Jokhang Monastery in Lhasa, Tibet were analyzed, using different techniques, including X-ray fluorescence (XRF), Raman microspectroscopy (Raman), polarized light microscopy (PLM), and scanning electron microscopy with energy dispersive X-ray spectrometry (SEM-EDS). It is found that azurite, malachite, red lead, cinnabar, mars red, orpiment, gold, calcite, magnesium carbonate, barium white, especially modern synthetic Ultramarine blue, emerald green, chrome yellow and lithopone were used as colorants on plaster. This result suggests that the wall painting may have been executed after the 1850s, mostly in about the 1900s.