Abstract:Bricks and tiles are ceramic building materials, which have been commonly used for palaces and other high-grade buildings since the Western Zhou Dynasty. During the Qin and Han Dynasties, with unification and centralization and the massive development of civil engineering in various places, the pottery industry tended to mature. In addition, the brick chamber tomb appeared in the late Western Han Dynasty, and quickly became popular nationwide in the Eastern Han Dynasty. All the factors above made pottery products for buildings occupy an important position in the pottery industry (with the name of “Qin bricks and Han tiles”). The Han Dynasties were a period of prosperity for the pottery industry, with the pottery products more widely used than in the Qin Dynasty, and the structure of brick and tile kilns changing as their functions changed. In order to explore the scientific logic of the changes in the characteristics and structures of Han Dynasty brick and tile kilns, numerical simulation of the flow field and temperature field during firing in Han Dynasty brick and tile kilns with different structures was conducted. Han Dynasty brick and tile kilns were semi-inverted-flame ones, with the advantages of rapid heating, long holding times and even temperature distribution compared to the earlier horizontal cavity kilns and rising-flame kilns. Through the analyses of archaeological reports and numerical simulations, the functional and structural relationships of Han Dynasty brick and tile kilns were studied. Firstly, based on the previous typological studies of Han Dynasty brick and tile kilns, the kilns were divided into single-flue and multiple-flue ones according to the pattern of change in the structure of each part of the kiln during the Han Dynasties. Then, based on excavations of kiln sites and documentation of the ancient kiln industry, the construction, yarding and firing methods of Han Dynasty brick and tile kilns were summarized. Finally, simulations were modeled based on the above research with the aim of investigating the influence of variation in the number of flues on firing in the brick and tile kilns. Furthermore, considering such factors as the unearthed relics, age and preservation in the kiln, Han Dynasty Kiln site Y6 at Sulin Village, Jiaozuo, Henan Province and Kiln No.11 at the Capital City site of the Eastern Zhou Dynasty in Luoyang were selected to carry out numerical simulations respectively. Han bricks were taken as examples of kiln products, the computational fluid software FLUENT was mainly used to simulate the flow field and temperature field in the kiln, and the flow of flue gas in the Han Dynasty kiln was analyzed from the perspective of fluid mechanics and thermodynamics. The results indicate:1) Han Dynasty brick and tile kilns were built in a semi-cavernous manner, with the walls rammed and coated with grass-mixed mud after excavation to create a flat shape. The roof of the kiln in the Western Han period was capped with a four-sided knotted dome or vault roof, while in the Eastern Han period the roof was capped with a four-cornered vault dome or vault roof. A side-standing arrangement of billets was adopted for yarding in the kiln; the firing temperature of the kiln was around 1 000 ℃. 2) The structural changes of brick and tile kilns in the Han Dynasties adapted to the expanding demand for ceramic building materials in society at that time and were scientifically reasonable. In addition, the flue gas flow characteristics of the semi-inverted-flame kiln were verified through simulation experiments, especially the structural change of the flue from one to many making the temperature distribution in the kiln more uniform to raise the firing temperature and improve the quality of bricks and tiles. 3) After preliminary research, it was found that, in Han Dynasty brick and tile kilns, a fire wall was set up between the firing chamber and the kiln chamber, which played a role in insulation and slowing down the flow rate of high-temperature flue gas. This structure was of great significance for firing large numbers of high-quality artifacts such as pottery figurines. According to this research, the structural changes in Han Dynasty brick and tile kilns are somewhat rational, with multiple-flue kilns having the advantage of being more insulated than single-flue ones, improving temperature distribution and insulation within the kiln chamber, increasing the firing temperature range and firing quality of products. This explains the logic of structural changes in Han Dynasty brick and tile kilns, namely that it corresponded to the needs caused by the rise of brick chamber tombs and large buildings during the mid- to late-Western Han period. These changes laid a technical foundation for the subsequent large-scale firing of ceramics with higher firing temperature conditions. The results demonstrate the feasibility of numerical simulations in kiln research and provide a scientific basis for further exploration of the production levels of Han Dynasty kilns.

Abstract:Tomb murals are among the most important painted cultural relics, and removal, reinforcement and restoration are main protection methods for them at present. During the removal, the digital recording and characteristic analysis of mural painting contents and pigments is an important basis for the subsequent reasonable restoration of the mural surface. The spectral imaging technology, as a means of information detection for synchronous perception of attributes and vision, can be used for the high-dimensional information recording and material attribute analysis of the pigment layer on mural surfaces. In addition, virtual restoration of pigment colors can be realized using the hyperspectral pseudo-color display technology. Based on this, a method for virtual restoration of the colors of mural pigments based on the spectral fusion analysis and band-pass energy integration is proposed and experiments on mural pigment recognition and virtual restoration of colors were carried out using collected pigment spectral data, mural hyperspectral imaging data and mixed pigment spectral data in simulated real scenes. According to the experimental results, for the red, yellow, blue and green pigments on the selected mural from Tang tombs, the spectral fusion recognition demonstrated that the red pigment from the tomb of Imperial Concubine Wu Hui was cinnabar/silver vermilion, the yellow one from the tomb of Han Xiu was orpiment/bezoar, the blue one from the tomb of Imperial Concubine Wu Hui was azurite/lazurite, and the green one from the tomb of Han Xiu was malachite. In addition, based on the above results, virtual restoration of mural pigment colors of pure color restoration and mural substrate rendering restoration were obtained. These results could provide a reference of the visual restoration of pigment layers for the physical restoration of murals. The above research results have important innovative and exemplary significance in the field of mural heritage protection and activation utilization.

Abstract:A kind of pale-blue substance was found on ancient textiles excavated from the Hejiazao Song Tomb in Hengyang, Hunan Province. In this study, we used a combination of SEM-EDS, LRS, XRD, XRF and OM for analysis. The results show that the substance was a ferrous phosphate mineral—vivianite [Fe₃(PO₄)₂·8H₂O], which is mostly formed under a reducing and sulfur-deficient but iron and phosphorus-rich environment. Microbial activities also affect its formation. The discovery of this mineral is instructive for studying the preservation state and environmental characteristics of the tomb. This mineral may be used to judge special burial conditions of archaeological remains.

Abstract:In March 2020, a number of microscopic carvings of the Wuzhou period were unearthed from Cemetery M19 at Xiaoju’an Village, Chang’an District, Xi’an. These artifacts are exquisite in shape, and since similar artifacts have rarely been unearthed, there are few relevant studies. In order to clarify the nature of their construction materials and methods of making, scientific analyses were carried out using super depth-of-field microscopy, portable XRF, SEM-EDX, and FTIR spectrometry. The results show that 1) the shaping and painting processes included scraping, drilling, polishing and gilding, etc.; 2) the main material was hydroxyapatite with calcium and phosphorus as major elements and honeycomb-like holes commonly existing after weathering, namely bone.

Abstract:Powdery rust of bronze ware—a “bronze disease”—is harmful. Since it seriously corrodes the matrix of bronze and is difficult to cure, and its malignant expansion can make an intact bronze completely crisp in a short time, it is also called a “bronze cancer”. With more than a century of in-depth research on the powdery rust of bronze, achievements from the composition of products of the specific process of reaction have been progressively promoted. However, the reported studies are mainly focused on the mechanism of corrosion and reaction, conditions of corrosion occurrence, detection methods for corrosion products and corrosion prevention and treatment for bronze ware. Transmission of powdery rust has rarely been discussed. To study the process of diffusion of powdery rust of bronze, an inspection box was designed and bronze samples with powdery rust were prepared by a simulation experiment, and the growth of powdery rust was recorded in real time. Then the aerosol particles in the box were determined by inductively coupled plasma-mass spectrometry, Raman spectrometry and neocuproine-absorbance. The results show that basic cuprous chloride was the main component of bronze powdery rust and the final product of the reaction of powdery rust formation. Cuprous chloride was the intermediate product of the reaction and was converted to basic cuprous chloride in the presence of oxygen and moisture. The aerosol copper ion content in the inspection box was significantly higher than the normal value. Combined with this observation, it is shown that the powdery rust growth occurred from the inside to the outside, and that the internal reaction would make the reaction product expand, and that growth and expansion would continue outwards until cracking. The products of powdery rust were mainly composed of a mixture of cuprous chloride and basic cuprous chloride, which were fine granular, mostly loose matters. Under the splitting and breaking force, rust powder turned into a completely irregular suspended substance with the air flow and fell into the surrounding environment. When in contact with other bronzes, the powdery rust would then “infect” them upon an increase of oxygen and moisture. Compared with previous literature, this study expands in the following aspects:1) it is pioneering experimental research conducted on the diffusing process of powdery rust, and it is shown that the powdery rust grows in a process of continuous expansion from the inside to the outside until the rust layer breaks; 2) this study has found that the aerosol fine particles (cuprous chloride and basic cuprous chloride) generated in this process will become suspended in the air and then settle, causing infection; 3) based on the experimental results, some suggestions are put forward for the restoration process and preservation environment of bronzes. This study provides support for the identification of bronze rust products and evidence for understanding the transmission of powdery rust by aerodynamics. It can also be a useful reference for the prevention of bronze powder. It greatly enriches domestic research results concerning the dispersion of bronze rust powder by aerodynamics, as well as provides new insight into the study of the corrosion mechanism of bronze. Furthermore, it can also provide a feasible method to decelerate the growth and infection of powdery rust.

Abstract:With the advancement of the conservation of ancient books and other paper cultural relics, research on the conservation of paper itself has made progress. However, by contrast, there is an urgent need to carry out studies on the preservation and conservation of writing materials such as ink and pigments on paper and their interactions. Investigation of the aging of ancient ink marks is focused on the essence of ink-paper interaction, which is of great significance for ancient book conservation. Using the ink marks on an ancient Chinese book collected in Fudan University Library as examples, we analyzed the phenomenon of ink yellowing in a multi-scale way using various non- and micro-destructive methods such as microscopic observation, surface pH testing, and micro-Raman and FT-IR spectrometry. The results show that compared with the blank fibers, the yellowed fibers at and around the ink marks lacked luster and were slightly decayed, more acidic and had more surface oxidation groups, indicating that the ink might have an impact on the aging and degradation of paper. This was further verified by a simulated aging experiment of soaking paper in ink. The results show that compared with neutral inks, acidic inks promote the aging of paper, with an obvious decline of pH value, tensile and folding properties, and a lower retention rate of degree of polymerization. The simulated aging experiment of ink characters supported the foregoing conclusions. Characters using more acidic ink had a stronger acidity and the chromatic aberration was also more significant. The above results indicate that the acidity of ink had a very important impact on the degradation of paper. In-depth research on this subject could not only reveal the mechanism of paper aging affected by ink during the preservation of ancient books, which would be helpful in understanding and formulating long-term strategies for the conservation of ancient books, but would also provide guidance for the development of ink for restoration.

Abstract:Wooden artifacts from Gansu represent the highest level of Han Dynasty carving skills in China. Being rotten is a typical feature of these wooden artifacts—usually the degree of cellulose degradation is up to 50%. The inherent properties and defects of the material and the sensitivity to the humidity and moisture in the environment easily cause the effects of “wet expansion and dry contraction”, which is harmful to the preservation and conservation in the later stage. In view of the disadvantages and issues in the current safety assessment technology, we conducted profound analyses of the methods, wood material characteristics and properties, and combed through relevant physical parameters used to measure and characterize material shapes and structure changes. We also applied modern analytical instruments and mature analysis technologies to observe morphology and analyze testing data of collected samples. The study result show that 1) the moisture content of the wooden core, as the determining factor affecting the structure and shape stability of rotten wood ware, was the only indicator of the safety assessment; 2) the volumetric weight, degree of fiber crystallization and of fiber degradation of the wooden core, as the characterization parameters considering material physical and chemical properties, objectively reflecting the actual changes of the material, could be used as a reference index for the quantitative assessment; 3) the safety change range of the moisture content of the wooden core was 9.3%~14.3%, with a safety fluctuation range of ± 5%. According to the above results, we made relevant definition standards for the safety assessment of rotten wooden artifacts:1) when the wood moisture content fluctuates and changes in the safe range, the characterization parameters change slightly, and the object is basically safe; 2) when the wood moisture content fluctuates frequently beyond the safe range, serious changes in the morphology and structure of the rotten wood often occurs, with the volumetric weight and fiber crystallization degree decreasing, and the fiber degradation degree increasing; 3) when the object loses the basic ability to maintain its balance effect—when the characterization parameters are extremely abnormal, especially when the lignin content reaches 85% and the cellulose is almost completely degraded—it is endangered. Finally, combining and combing through the analysis results, we designed and created a scientific and standardized framework of the safety assessment technology for rotten wooden artifacts. The technology not only adopts the combination of quantitative and qualitative ways, with the characterization of being data and evidence-oriented, but is also simple and practical.

Abstract:Overall relocation has been selected for more and more undamaged high-value tombs. However, there are still a large number of incomplete (partial structural defects) but high-value tombs that need to be preserved. A rare Song-Jin carved-brick tomb, as an important supplement for the study on tomb types and burial customs in the Song and Jin Dynasties, was found in Xi’an, and relocation conservation was considered to take it as an example to explore the overall relocation conservation method for such structure-defected tombs. To keep the tomb structure, based on the physical modeling of centroid offset correction and wall overturning risk analysis, the center of mass and its influence during relocation was calculated, leading to the plan of keeping some soil outside and add fill inside. Then the width and height of the soil remaining outside was calculated based on modeling. Furthermore, before following the guide above, an experiment to select materials and techniques for painting layer protection was conducted, to ensure the successful overall relocation of the tomb. This overall relocation conservation is an attempt to utilize physical modeling to evaluate risks and give a scientific guide for ensuring the stability of structural defects in high-value tombs. It is also an exploration of the standardization of conservation methods for overall relocation of structure-defected tombs. This method could provide a reference for the conservation of other similar tombs.

Abstract:Moisture is a key factor causing diseases of wall paintings. The amount and characteristics of evaporation in Cave B113 of Dunhuang Mogao Grottoes have been monitored for 5 years by the condensation method in an enclosed environment. The results show that the annual evaporation of water was 61 189.9 g and the daily evaporation was 229.2 g in Cave B113, both presenting the characteristics of sinusoidal curves. The monitoring shows that the evaporation of water in the cave increased with the rise of temperature, and vice versa. The temperature determined the concentration of evaporative water vapor, and the outflow of earth-air determined the volume of evaporative water vapor; both determined evaporation. Evaporation lasted from April to mid-December in the cave, with the largest evaporation occurring in June, July and August. Daily water evaporation rose rapidly from 7∶00 to 12∶00, and decreased from 12∶00 to 23∶00. There was also continuous water evaporation at night. It was the temperature and the amount of earth-air activity that dominated and controlled the amount of evaporation in the cave. The revelation of the water evaporation mechanism in caves provides a theoretical and scientific basis for the regulation of the micro-environment and the preventive conservation of wall paintings in the future.

Abstract:Regional stability monitoring is an important measure for the long-term conservation of grottoes. In this study, the North Grotto Temple in Qingyang was taken as the object. Based on the Sentinel-1A satellite radar images of 15 scenes in 2019, the SBAS-InSAR technology was used to monitor the stability of the studied area. In addition, the radar line of sight deformation rate and time-series deformation in the studied area were obtained. The spatial and temporal distributions of deformation in the studied area and the causes were also analyzed. The monitoring results show that 1) Fuzhong Mountain was stable, as a whole, with small deformation but no characteristics of potential landslide deformation; 2) the main deformation areas in the studied area were distributed along rivers, with the most obvious deformation appearing at the junction of Pu and Ru Rivers; 3) the regularity of time-series deformation in the studied area varied with season, and was due to soil erosion and the implementation of the project for gully consolidation and tableland protection at Dongzhi Tableland. This study has demonstrated the feasibility of the InSAR technology for the regional stability monitoring of cultural heritage sites. Its advantage of long-term reliability provides a new idea and method for the long-term preventive conservation of grotto temple sites.

Abstract:The sky-blue glaze is a kind of precious monochrome glaze in ancient China. It was generally believed to have originated from the legendary Chai kiln, but up to now, the earliest sample appeared at Ru kiln. Therefore, some scholars believe that the sky-blue glaze is a unique product of Chai and Ru kilns before the Southern Song Dynasty. However, in recent years, other scholars pointed out that the sky-blue glaze is not the “patent” of Chai and Ru kilns, and that the earliest sky-blue glaze might have originated from Yaozhou kiln in the Five Dynasties. In this work, we first classified the so-called sky-blue glaze samples from Ru kiln in the Northern Song Dynasty and from the second stage of Yaozhou kiln in the Five Dynasties according to the experience in cultural relics. We then measured and compared their chromaticity values, in order to discuss the provenance and origination time of the sky-blue glaze.

Abstract:Maijishan Grottoes were first built in the Later Qin Dynasty of the Sixteen Kingdoms Period and have been excavated and repaired for more than 1600 years, showing distinctive features of the times. During the Northern Wei Dynasty, Maijishan Grottoes gradually formed a style integrating the cultures of Buddhism and Central Plains. At present, relevant research is mainly focused on the artistic style of grotto statues and murals. Cave 131 was excavated in the late Northern Wei Dynasty and has been covered with a layer of smoke pollutants. The contents of its murals are still unknown, but the murals have a large hollow area and have started to fall off. The raw materials and production technology for murals are indispensable data and basis for their scientific research, protection and restoration. However, according to the existing literature, scientific research on the materials for murals of Maijishan Grottoes is scarce, and that on their production technology is basically blank. In this study, we conducted a scientific analysis of the ground support layer, and its additives and pigments, of Cave 131 mural fragments using the suspension sedimentation method and fiber morphological observation, in combination with laser particle size analysis, XRD, XRF and Raman spectrometry, etc.  The results indicate that 1) the smoke pollutants on the mural surface were thick, tightly adhering to the pigment layer and penetrating into its interior, and there was a serious cracking problem; 2) the internal hollowing out between the pigment layer, base layer and ground layer of the murals is a serious hidden danger; 3) clay used for the ground layer was a natural fine loess collected from a relatively more distant area around Maiji Mountain; 4) in the fine mud layer, washed fine sand and hemp fibers were manually added, while in the coarse mud layer, more and larger uneven sand and unwashed wheat straw were added, which could effectively reduce the shrinkage and cracking of the ground layer. The main expansion of this study includes the following three aspects:1) the smoke pollutants tightly adhering to the mural surface were one of the factors that caused the peeling of mural layers, and the coverage of smoke pollutants could delay the corrosion and blackening of lead, providing a reference for later research on corrosion and protection; 2) through the analysis, it was found that the particle size distribution of loess soil samples collected was obviously different, while the particle size distributions of the mural samples and Dianzi Village loess soil samples were consistent, so it was speculated that high-quality clay areas from far away were collected as the raw material for the ground support layer of murals in Maijishan Grottoes; 3) the particle size distribution of natural loess sand was highly consistent, far less than the particle size distribution of soil samples from the ground support layer, which could determine the gravel addition and processing methods in the ground support layer, and to some extent, it has solved the problems of soil sample sources and processing measures for the ground support layer of murals in Maijishan Grottoes. This study provides a reference for exploring the materials and production technology for murals in Maijishan Grottoes, and also provides a scientific basis for the subsequent analysis of mural diseases, protection and restoration.

Abstract:Raman spectrometry and SEM-EDS were applied to analyze six typical samples of pigments from the stone coffin in the tomb of Yang Hui of the Tang Dynasty. The results show that all pigments were mineral ones:the green one was malachite, the white one white lead, the black one carbon black, the brown one a mixture of red lead and litharge, the red one cinnabar and the pink one a mixture of red lead and white lead. All the pigments were well-preserved and no chemical change was found. This study could provide important information for the research on relevant subjects of archaeology and conservation.

Abstract:The study of the mildewing of textile relics plays an important role in their conservation, restoration and storage. In order to identify the microorganisms causing mildewing of textile relics in the collection and investigate the fungal disease characteristics of cotton textile relics, the potato dextrose agar (PDA) medium was used to isolate and purify the microorganisms extracted from the mildewed parts of cotton textile relics. The purified molds were analyzed by 18S rDNA-internal transcribed spacer (ITS) sequence. The National Center for Biotechnology Information (NCBI) sequence database was used to compare sequence homology and construct a developmental tree. Finally, a total of six strains of mold were isolated, purified and identified by sequencing as Penicillium, Alternaria, Aspergillus, and Fusarium. In this study, morphological methods combined with molecular biological measures were used to isolate and identify the microorganisms causing mildewing of cotton textile relics, making the results more rapid and accurate. In combination with the current conservation status of textile relics in museums, the conclusion of comprehensive conservation measures for cotton textile relics was put forward, which could provide a theoretical basis for the mildewing prevention work of such cultural relics and the development of mildewing-resistant materials.

Abstract:By exploring the processes of making lacquered wood artifacts, especially the lacquering process, we can obtain important information useful for the conservation and restoration of cultural relics. The preservation status of two gold lacquered wood carvings to be exhibited was assessed using X-ray fluorescence spectrometry, infrared spectrometry and laser Raman spectrometry, micro-morphology analysis and X-radiography. Based on the testing and analysis results, and in compliance with the basic principles of cultural relic restoration (such as not changing the original state of cultural relics, minimum intervention and authenticity, etc.), we conducted conservation and restoration by cleaning and disinfecting the two artifacts, complementing and coloring the wooden cores, reattaching and completing the lacquer layer, which had serious warping and was falling off. After this treatment, the artifacts are in stable states and show certain durability. These efforts have achieved the purposes of exhibition and safe, long-term storage.

Abstract:Paper is an important information carrier in the Chinese civilization, and paper deacidification in the liquid phase is the optimal way to deal with acidification and delay deterioration of paper. Actually, in order to achieve remarkable deacidification effects, it is necessary to prepare deacidification solutions with excellent performances for removing acid and retaining alkali as well as adopting appropriate techniques to maintain paper appearances. In view of this, a detailed investigation of major liquid-phase deacidification works both domestically and overseas over the past ten years is presented and discussed in this article. Based on this, influencing factors from five aspects—wettability, dispersibility, reinforcement, antimicrobial properties and anti-wrinkling technique—are sorted out, and then the corresponding countermeasures are also summarized, to provide some reference for the follow-up research.

Abstract:This article systematically summarizes dry cleaning techniques for paper document conservation and restoration. It introduces ten frequently-used techniques and their corresponding tools, materials and operation processes, and then briefly evaluates their existing problems, advantages and disadvantages. In addition, the principles and research status of three cutting-edge cleaning techniques are also reviewed.

Abstract:Paper is an important carrier of human historical and cultural information, and the proper preservation of paper cultural relics is part of the continuation of civilizations. Paper products can be damaged due to natural aging and fungi-based microorganisms during their use and storage. Disinfection of paper is an important step in the conservation process. This paper summarizes the hazards of microorganisms to paper products and the common chemical and physical disinfection methods, focuses on the disinfection effects of ionizing radiation on paper products, and analyzes the influences of radiation on the mechanical properties, color and degree of polymerization of paper.

Abstract:The key to controlled freezing disinsection is control. The control indicators include freezing temperature, cooling rate and freezing time. The purpose of control is to achieve pest extermination. The freezing temperature and cooling rate directly affect the physical safety of frozen objects, so controlled freezing disinsection with the prerequisite of ensuring the safety of objects requires risk management. Based on literature analysis, laboratory investigations and theoretical studies on related issues, it is found that the risk of incomplete pest extermination will occur when the temperature is not low enough, the cooling rate is not fast enough, and the freezing time is too short. The damage to objects caused by the extreme low temperature and rapid cooling is related to the material properties of the frozen objects, so materials that are inevitably damaged under the extreme low temperature and thermal shock should be excluded from freezing disinsection. Selecting freezing temperatures in a scientific way and strengthening the control of the freezing disinsection process could eliminate its risk and ensure pest control as well as the safety of the collection.

Abstract:The stability of archaeological relics can be completely non-destructively checked by measuring oxygen consumption. The rapid consumption of oxygen indicates an unstable state of a sample. In this work, the basic principle, influencing factors, scope of application and applicable objects of the optical sensor-assisted oxygen consumption method are summarized. The measurement of oxygen concentration by optical sensing is based on the fluorescence quenching of oxygen. This method can quickly and accurately reflect the oxygen consumption rate of archaeological relics, showing great significance for evaluating the preservation state of cultural relics. The monitoring system is affected by such factors as the relative humidity, temperature, atmospheric pressure and light. Appropriate monitoring systems are selected according to the size and morphology of cultural relic samples to monitor all the oxygen consumption reactions, so this method has greater portability and general applicability. Therefore, the optical sensor-assisted oxygen consumption method can be used to evaluate the effectiveness of conservation materials and measures.