Abstract:Minium (Pb₃O₄) and cinnabar (HgS) were commonly used as red pigments on paintings in ancient times. The discoloration of these red pigments has been a long-term concern for conservators, curators and art historians. However, it is difficult to study the degradation mechanism of these historical materials because of their long time exposure to the environment and complex decaying factors. To investigate and monitor the process of photodegradation of minium, cinnabar and their mixtures, an electrochemical setup with a pigment-modified graphite electrode was used. It was confirmed that light irradiation of minium induced a reductive photocurrent, while an oxidative photocurrent was detected for cinnabar. In this work, the photochemical reaction of the mixed pigment of minium and cinnabar was determined to be a reduction process. Both pure and mixed pigments having experienced ultraviolet aging were analyzed by Raman and X-ray photoelectron spectroscopy (XPS). Minium was partly converted to cerussite (white lead) and hydrocerussite after UV light aging. The reaction kinetics results show that the addition of cinnabar into minium might accelerate its photodegradation reaction.

Abstract:Dust and contamination on the surface of textile relics are common diseases. Dust removal has become a very important part in the conservation and restoration of handed-down textile cultural relics. For a variety of cultural relics, how to remove dust safely, effectively and conveniently has become the direction of our research. This study mainly focuses on the dust removal method for a lake blue satin embroidered lying sheet with a phoenix pattern, which was stored in Ti Shun Tang (Hall of State Satisfaction) of Yang Xin Dian (Hall of Mental Cultivation). Firstly, existing physical dust removal methods for textile cultural relics, including the vacuuming, wiping, vibration, adhesion and gel methods, are summarized in the paper. Secondly, we carried out a comprehensive study of the object, including analyses of production techniques, patterns, diseases and other testing and detection. The results show that 1) the object was double-layered with silk lace, and the surface was mainly embroidered with flower and bird patterns by non-twist yarn and twist yarn; 2) it was speculated to have been produced in the late 19th or the early 20th century based on the acid azo dye found in the yellow yarn; 3) embroidery threads had good fiber strength, though the fabric was partially decayed, so dust removal could be carried out. Thirdly, dust removal methods were compared using a special museum vacuum cleaner and dust removal equipment with negative pressure and liquid filtration and microfiber fabric. The dust removal method determined is as follows:using a museum special vacuum cleaner for the first preliminary dust removal, followed by the dust removal equipment with negative pressure and liquid filtration for the second fine dust removal. The local parts of the object were classified as satin fabric, cracked fabric, embroidery thread intersection, embroidery pattern edge, the thin gap between embroidery pattern, non-twist yarn embroidery, twist yarn embroidery and seed embroidery, according to the characteristics of the weaving and embroidery, and a study and analysis of the dust removal. Compared with previous studies, the analyses of the object in this study are more specific and in-depth, focusing on the technical characteristics, experimental detection and dust removal techniques. In the dust removal experiments, the dust removal effects were observed with the help of microscopes, which was conducive to the selection of dust removal methods. Before and after dust removal, the color data of each part were compared with the help of a colorimeter to check the effects of dust removal. In the process of dust removal, three-dimensional space structures formed by fiber weaving and embroidery techniques were analyzed. In combination with the characteristics of the dust removal equipment with negative pressure and liquid filtration, the dust removal techniques of different parts are described in detail. In this paper, physical dust removal methods for handed-down textile relics are reviewed. The dust removal methods for embroidered textiles are further analyzed. This work can be used as a reference for the selection and operation of dust removal methods for similar cultural relics in the future.

Abstract:Cultural relics possessing historical, artistic and scientific value were left by human beings in social activities. Three-dimensional (3D) reconstruction is a feasible solution of profound significance for the preservation and management of cultural relics. However, the existing methods such as 3D-laser scanning and structured light need improvement. The method of digital close-range photogrammetry can satisfy the accuracy requirements while ensuring low cost and high efficiency. How to apply photogrammetry to the rebuilding of cultural relics and to manage them for appreciation, restoration and dating is very important for the conservation and inheritance of objects of excellent material cultural heritage. This study proposes a vision-based 3D modeling scheme, which is divided into three steps:classification of Ming and Qing furniture, data acquisition and high-accuracy 3D-reconstruction, and establishment of high-accuracy 3D-digital cultural archives. Firstly, according to the cultural characteristics of Ming and Qing furniture, we conduct hierarchical classification management survey and build a unique coding system; secondly, based on digital close-range photogrammetry, we propose a low-cost and high-efficiency method for non-contact data acquisition; thirdly, we extract patterns, components, and structures from 3D-information and build an index based on coding; finally, we create the digital cultural archives and build a sharing platform on the Internet. This study experimented with 100 sets of Ming and Qing furniture miniatures. The accuracy of the digital model was controlled to the level of a millimeter. The extraction of cultural relic elements, construction of classification framework, management of attribute information and design of index structure were carried out to form an information database integrating digital models and their culture. The method we propose can achieve high-accuracy 3D-reconstruction, reduce costs, improve efficiency and help to preserve cultural relics. The 3D-digital cultural archives can be used for the management and study of ancient Ming and Qing furniture. We consider combining artificial intelligence with our method to customize modern furniture, advance our technology, apply it to more small cultural relics in the future and support the construction of digital museums.

Abstract:Lacquerware of the Western Han Dynasty has high artistic, historical and social value, but artifacts from archeological excavations are often seriously deformed due to burial for a long time. Because of this, it is very difficult to obtain low distortion images of structures and ornamentation of lacquerware, which directly affects the authenticity restoration of lacquerware. Taking a large lacquer box from the tomb group of the family of Zhang Anshi at Fengqiyuan in Xi’an as the research object, we successfully obtained the specification, shape and decorative patterns of the Western Han lacquer box by means of three-dimensional scanning, multi-angle two-dimensional photography, non-contact stereoscopic measurement and other digital techniques and methods, and by the intersection, fusion and comparison of multiple technical methods. This research lays a foundation for the authenticity restoration of highly-deformed unearthed lacquerware.

Abstract:In order to explore the differences in raw material selection and processing techniques used for pottery-making during the Western and the Eastern Zhou Dynasties at Guanzhuang site, Xingyang, Henan Province, we studied the materials and blanks of sandy and clay pottery, Holocene paleo-soil, Malan loess, and river sands from Ku River near the site. Samples were analyzed using a particle size analyzer, a magnetic susceptibility meter and an X-ray fluorescence (XRF) spectrometer. The results show that 1) earthenware clay of Guanzhuang pottery came from the sedimentary strata dating to the late Pleistocene and Holocene, where Guanzhuang site is located; admixture of the sandy pottery clay and blanks are mainly river sands taken from the channel of Ku River; 2) during the use of the site, techniques for the selection and processing of pottery clay differed from the early to the late periods. In early days, clay from Malan loess or Holocene paleo-soil was elutriated (1~11 μm) and then mixed with river sands to make sandy pottery. The proportion of coarse-grained river sand to fine-grained clay is 1∶4; in the later period, Holocene paleo-soil was used as the earthenware clay, and was prepared directly or only after a simple elutriation process.

Abstract:Blue-and-white porcelain is an important category in the history of Chinese ceramics. Since its rise, more than six hundred years ago, the production of blue-and-white porcelain has left abundant cultural resources. Many museums and cultural heritage preservation institutes have huge collections of blue-and-white porcelain objects. However, due to the fragile nature of porcelain wares, these objects often suffer from deterioration including physical damage and loss, which severely affects their visual perception on display. Restoration methods for the purpose of artistic display play an important role in bringing the damaged blue-and-white porcelains back to the public’s view, of which retouching is the key, as well as a challenge. This study intends to propose practical techniques and methods for retouching of blue-and-white porcelains, through observation and analysis of the body and glaze, the raw materials of cobalt blue, the painting techniques for decorative motifs, the detailed features of decorations and the conditions of damage. It is hoped that these retouching techniques and methods will enable the blue-and-white porcelains to receive proper treatment and to meet the standards of artistic display.

Abstract:The paper records the entire process of arrangement and conservation of bamboo slips and wooden tablets excavated from Tomb M8 of Zhoujiazhai Cemetery in Suizhou, Hubei Province. To meet the requirements needed for character recognition and information acquisition, we designed the methods for arrangement and conservation of bamboo slips and wooden tablets. Our professionals divided all of the tomb goods—bamboo slips and wooden tablets covered by mud—into several categories and separated the bamboo slips and wooden tablets, which were badly deteriorated, then cleaned and decolorized the slips and tablets to their natural colors. In addition, we explored the working mode of scientific excavation and timely arrangement and synchronous conservation of waterlogged slips and tablets excavated from tombs in south China. This work provides some experience for the conservation of similar cultural relics in the future.

Abstract:Monk Budai by Muxi of the Southern Song Dynasty in the collection of Tokyo Art Club is a valuable and rare work, but it has a severely flocculated surface with fractures and mildew spots, as well as partial loss of the picture and detachment of the mount. This article first discusses the criteria for selection of paper used for the restoration of the painting, from the aspects of paper categories and characteristics found in ancient paintings and calligraphy. In our study, we analyzed the physical and chemical characteristics of the original paper of the painting using modern instruments such as a Fourier transform infrared spectrometer, a pH meter and a microscope, and then conducted a comparison and analysis of five types of repair paper—Xuan paper made in three different times, hemp paper and modern mulberry paper—according to their fiber composition and their physical and chemical properties. We found that the modern mulberry paper matched the original work of Monk Budai best, so modern mulberry paper was chosen for the restoration of the original work. The preparation of the repair paper and the restoration of the work provide a scientific basis and reference for subsequent conservation and restoration.

Abstract:The interior decoration of Yang Xin Dian (Hall of Mental Cultivation) of the Palace Museum was achieved with a variety of materials, among which are paper-based artworks including Tieluo (wall paper-sticker decoration) and the decorative calligraphy and paintings on the partition doors and windows of the imperial architecture compound. Tieluo are concentrated in the main hall, the east and west pavilions and the Buddha hall. In the project of the conservation of Yang Xin Dian, conservators of Chinese paintings and calligraphy carried out a comprehensive investigation in the area. Tieluo “longevity” was pasted on the wallpaper in the Buddha hall of Yang Xin Dian. The painting paper of the Tieluo is yellow powder-wax paper drawn with silver dragon and cloud patterns. In order to study its structure and techniques, multi-angle photography was used to analyze the status of the Tieluo. The structure of the powder-wax paper was analyzed by cross-sectional observation, scanning electron microscopy-energy dispersive spectrometry (SEM-EDS), combined with micro-infrared spectroscopic mapping; the yellow dye was analyzed by high performance liquid chromatography-mass spectrometry (HPLC-MS); the fiber morphology of the backing paper was observed using microscopy. This is the first study of the structures, materials and techniques of the Qing Dynasty powder-wax paper, and provides a scientific basis for the research on the conservation of this kind of processed paper.

Abstract:Bronze artifacts unearthed from Liujiawa site, Chengcheng County, Shaanxi Province are of great value for studying the history of the state of Rui in the early Spring and Autumn Period. However, due to the long-term corrosion of the bronzes, some of the information contained in the artifacts may be lost. A comprehensive research on the causes of corrosion of Liujiawa bronzes was conducted in order to investigate the production techniques used and status of preservation and stability of Liujiawa bronzes, to reveal the characteristics of soil corrosion of bronzes unearthed in the Loess Plateau of eastern Guanzhong Region, and to provide a reference for the conservation and restoration of bronzes. The phases and structures of the corrosion products of six bronzes excavated from Liujiawa site were analyzed using metallographic microscopy, scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDS), X-ray Diffraction (XRD) and Raman spectrometry. The results show that the corrosion products of bronzes are mainly cuprite, malachite and cerussite, but no copper trihydroxychloride. The corrosion structure of Liujiawa bronzes has a four-layered structure including an altered layer, a non-metallic layer under the original surface, (the original interface), an in-situ deposition layer on the original surface and a diffusional deposition layer. The ratio of Cu/Sn in the non-metallic layer under the original interface is lower than that of the sound metal, which indicates that the copper in the matrix has migrated outward while cassiterite is formed and deposited in-situ after corrosion. The ratio of Cu/Sn outside the original interface is significantly higher than that of the non-metallic layer under the original interface, indicating that the migrating copper ions were deposited under the burial environment. The pH values, redox potentials and ion chromatograms of the soil samples attached to the bronzes were analyzed. The results show that the burial environment was alkaline and oxidized with a low concentration of Cl-, which account for the corrosion state of the bronzes. Therefore, the corrosion products of the bronzes could be preserved to reflect their historical, technical and artistic value. Additionally, attention should be paid to the temperature and humidity during later preservation, due to the fact that some bronzes unearthed from similar burial environments in Shaanxi have suffered from the bronze disease according to the poor preservation conditions.  Compared with the previous research on the corrosion of bronzes unearthed in Shaanxi, we put forward the following conclusions:1) due to the continuous occurrence of local corrosion inside the bronzes, the corrosion property of each reaction zone is constantly changing, so the reaction environment inside the bronzes is not equivalent to the soil burial environment and is weakly acidic. On this basis, through the calculation of the solubility of corrosion products under different pH conditions, it is determined that copper and lead exist in the ionic state and migrate under weak acid corrosion conditions inside the metal, whereas cassiterite may only be dissolved under strong acidic conditions; 2) based on the analysis of the tin contents in the corrosion layer, we believe that the relatively pure cuprite layer on the surface of some bronzes is formed by the weak migration of cuprous ions and in-situ deposition outside the original interface of the bronze. The original surface of the bronzes is located between non-metallic layer and the cuprite layer. The corrosion structure of the bronzes from Liujiawa site represents the corrosion characteristics in alkaline and low-chlorine burial environment, which is significant in revealing the relationship between corrosion and environment. The differences in the migration and deposition process of bronzes after metal oxidation to ions in different burial environments can provide a reference for different corrosion structures of bronzes unearthed from different regions in China.

Abstract:The safety of Fengxian Temple at Longmen Grottoes has long been threatened by weathering and water seepage. An infrared imager was used to monitor the head area of the Ananda stone statue at Fengxian Temple and the water-seepage area on the south side of Locana Buddha for one year, and many infrared images were collected and analyzed using MATLAB image-processing techniques. The results show that there is a cyclic thermal stress caused by temperature difference at the fissure of the Buddha’s head. This temperature difference mainly comes from the difference in thermal conductivity between the grouting area and the rock; the change of thermal stress is the most significant around the morning of a sunny day. The temporal pattern of water seepage during the monitoring period was summarized, and the degree of water seepage in different areas was statistically calculated. The combination of infrared imaging and big data analysis was applied to the preventive conservation of the grottoes in order to achieve the image monitoring and statistical assessment of deterioration simultaneously. This work provides a reference for the monitoring and data analysis work at other grottoes.

Abstract:The mercury isotopic compositions of 11 cinnabar samples collected from tombs at Shuangyuan Village, Qingbaijiang District, Chengdu, were determined. The results show a similar isotopic fractionation, ranging from -1.18‰ to -0.84‰ (avg.-1.010‰, S.E. 0.105‰, n=11). Compared with published data of some cinnabar ores, these fractionation numbers are different. In the future, these numbers may help to identify possible mineral sources of the Shuangyuan Village samples if mercury isotopic compositions of nearby cinnabar mines are analyzed.

Abstract:Flash photography has long been banned in museums, but the effect of flash on collections is controversial. There is little research in this area, either at home and abroad, and the experiments that have been conducted do not give a true picture of how visitors use the flash in museums. Besides, the evaluation indicators of the experiments focus on chromaticity. To properly evaluate the effect of flash on collections in museums, a preliminary field study was conducted on the use of flashing lights in museums, with Shaanxi History Museum, which has a large number of visitors, being a representative. The analysis of data showed that approximately 2.4% of visitors would use flash once on a specific collection. Our experiments were conducted using fluorescent lamps, in accordance with Code for Lighting Design of Museum, as the light source for museum displays, and using silk fabric dyed with the plant dye, cyanine, as an example to simulate light-sensitive collections. A total of 823 011 lx·h exposures were irradiated to the fluorescent lamp-group samples, and 350 166 flash lamp exposures were given to the flash-group samples. A colorimeter, a material testing machine, a scanning electron microscope (SEM) and a Fourier transform infrared spectrometer (FTIR) were used to detect the degree of aging of the samples and to investigate the effect of flash on the dyed silk fabrics. The results show that 1) the color changes of the samples were less than 1.0 in both sets of experimental conditions, indicating almost no change in appearance; 2) the tensile strength of all the samples decreased by less than 10%(9.56% in the fluorescent lamp group and 2.54% in the flash group), with the fluorescent lamp group showing a greater decrease; 3) it was observed by SEM that the fibers of the samples were not broken and there is no obvious difference in the micro-morphology before and after aging; 4) according to the structural analysis by FTIR, the —Gly—Gly— peptide chain structure at 975 cm-1 was degraded, and the fluorescent lamp group degraded more than the flash one; —CH₃ symmetric variable angle vibration was produced in neither of the groups; light aging caused the samples to undergo oxidative degradation, and the degree of oxidative degradation in the fluorescent lamp group was greater; according to the secondary structure analysis, the β-sheets in the crystalline region were slightly degraded in both groups, and the relative content of the fluorescent lamp group decreased more. The study results indicate that when the illuminance of the display light source is 50 lx, with 10 000 visitors a day to a museum, the effect of fluorescent lamps on dyed silk is more severe than that of flash ones. In terms of the number of museums and visitors nationwide, the impact of the flashlight used in 14.49 million visits on dyed silk fabrics, which would take 308 years on average, is slight. Although the traditional view is that “flashlights harm cultural relics”, this study shows that based on the current visiting conditions of Chinese museums in the field research, fluorescent light sources that meet the requirements of Code for Lighting Design of Museum have a more harmful effect than flashing lights.

Abstract:In a special action against cultural relic crime in Shanxi Province in 2019, a Han Dynasty gold and silver-gilded bronze bottle was recovered. The inside of the bottle is a layer of wood inner wall. It is a precious cultural relic showing a combination of wood carving, split casting and gilding. Super-field video microscopy was used to observe the surface morphology of the bronze bottle and inner wood to obtain micro traces left during the manufacturing process; X-ray imaging of the whole bronze bottle was used to observe its internal structure more accurately; X-ray fluorescence spectrometry was used to analyze the alloy composition of key parts, such as foot, belly and neck on the outer surface of the bronze bottle, so as to determine the decoration process of the surface and restore the complete manufacturing process. The results show that the bronze bottle was made by split casting, which includes the making of molds, cores, and clay outer molds, as well as casting, wood cutting, suiting and gold and silver gilding. The bronze bottle has two parts, which are combined by hoop and buckle. The body of the bottle was made of tin bronze, the gold part on the outer surface was gilded with gold, and the silver part on the gold layer was a thin layer of silver; the wooden body in the bottle was made using a whole piece of wood rather than by splicing. In this study, a gold and silver-gilded bronze bottle with a wooden body, which is rare in shape and techniques, was selected to fully study the methods for its processing. These results were confirmed in combination with the known history of development of bronze techniques. This work provides a scientific basis for the conservation and restoration of such complex and rare bronze wine vessels.

Abstract:Capillary water theory cannot explain the formation of efflorescence belts near the ground in arid zones. In this paper, the mechanism of formation of efflorescence belt is revealed based on the earth-air research at Dunhuang Mogao Grottoes. During atmospheric fluctuations, there is frequent air exchange between the atmospheric air and earth-air. When atmospheric pressure rises, the volume of earth-air is compressed, and the dry atmospheric air enters the soil. When atmospheric pressure drops, the damp earth-air is inflated and rises, reaching a certain height in building walls. During long-term and frequent alternation of dry and wet air, a large number of soluble salts in walls crystallize and dissolve repeatedly, causing the degeneration of near-ground buildings. In addition, the relatively intense flow of air and particles within pores has strong erosive effects on buildings. Therefore, it is earth-air that causes efflorescence belts, and the height of a belt is proportional to the amplitude of diurnal fluctuation of atmospheric pressure and the thickness of a vadose zone and is inversely proportional to the local atmospheric pressure. The revelation of the mechanism of formation of efflorescence belts based on earth-air provides a solid scientific basis for the prevention, control and moisture-proofing of building efflorescence belts, and also the maintenance of soil sites.