Abstract:In view of the potential damage caused by desalination and salt control methods widely used for salt-containing silicate cultural relics, a variety of instruments such as scanning electron microscopes, resistance meters and high resolution cameras were used to record changes of the distribution of salt zones in the interior of saline cultural relics with chromogenic copper sulfate solutions. The results indicate that the migration and diffusion rate of salt ions in the samples could be accelerated by desalination and surface-spray salt control methods, forming two or more layers of salt crystals in the interior of the samples. The formation of salt crystal band was related to the structural characteristics of the porous samples, the transport and evaporation rates of salt solutions and the frequency of humidification and drying cycles. The results also indicate that with the increases of capillary rise height and air permeability of the samples, ambient temperatures and salt concentrations and even humidification and drying frequency, the changes of salt band distribution in the porous samples became more obvious. The results provide scientific evidence and visual data support for the potential damages of porous cultural relics induced by desalination or salt control with the humidification technology.

Abstract:In this work, safflower (Carthamus tinctorius L.)-dyed textiles were taken as main research objects in order to study the degradation of carthamin, a coloring matter, under the influence of several color fading factors through two accelerated ways of light aging including UV and LED. The results show that hard and soft acidification effects produced different by products. Tricoumaroyl spermidine, as a kind of phenolamides, which was reported abroad as Ct4, was identified from safflower pollen grains for the first time by liquid chromatography-mass spectrometry (LC-MS) and could be used to distinguish between modern and ancient processes as a dyeing indicator. Taking two pieces of safflower-dyed textile relics from the Palace Museum collection as examples, the color fading mechanism was speculated out that the degradation of carthamin produced several products which increased the relative content of tricoumaroyl spermidine and resulted in obvious color fading and orange color of the front. The research result emphasizes that more attention should be paid to indoor pollutant acid air of volatile organic compounds (VOCs) for the same type of cultural relics.

Abstract:The silk industry in China has lasted for thousands of years. Having great value in history, art and science, unearthed silk relics recording the brilliant history of China are important elements in the ancient Chinese civilization. However, during excavation and preservation, silk relics are prone to being contaminated by microorganisms, especially mold, and the destruction is terrible and irreversible for silk relics. Investigation of these organisms can help us understand the current situation of contaminated silk relics,and help to find new mold inhibitors. Effective fungicide screening lays a foundation for the conservation of silk relics and the development of mold-prevention technology. Four mold strains were isolated and purified from silk relics in Suzhou Silk Museum and were designated Strains A, D, H and K. Then, the four mold strains were identified by morphological observation and molecular biological methods. In addition, the Oxford cup method was used to determine the activities of four fungicides (IPBC, MIT, BIT and PHMG) as inhibitors of these strains. According to the colony morphological characteristics, conidial morphology in PDA plates and molecular identification results, the four mold strains were classified into three genera, namely Aspergillus, Arthrinium and Cladosporium, of which Cladosporium was the dominant genus causing mold contamination. Strain A was identified as Arthrinium, Strain D as Aspergillus and Strain H and K as Cladosporium. The inhibition test results indicate that different isolates had different sensitivities to the fungicides. The fungicidal circle experiment showed that both MIT and IPBC had strong fungicidal activity against all the four mold strains. MIT had the strongest activity, with EC₅₀ values of 56.2 mg/L, 292.2 mg/L, 190.0 mg/L and 62.7 mg/L, respectively. The second strongest was IPBC, with EC₅₀ values of 250.3 mg/L, 27.5 mg/L, 480.3 mg/L and 997.2 mg/L, respectively. BIT and PHMG had relatively lower activities as inhibitors of the four strains. The present results of this study show that MIT and IPBC were suitable fungicides for inhibiting mold contamination of silk relics. Isolation and identification of these microorganisms could help prevent the growth of mold and provides a reference for the research and development of silk relic conservation.

Abstract:Oil stains on handmade paper is a common disease of paper relics, but there is little research on how this disease affects the permanence of handmade paper. In this study, the change in paper durability was taken as the breakthrough point, and the coexistence of oil stains and paper was observed by scanning electron microscopy, so as to determine the influence of oil stains on handmade paper. The results show that oil stains can affect the physical properties of paper to a certain extent, increase the color difference values and decrease the pH values. Moreover, oil stains wrapped on fibers to affect the paper in a way of physical adsorption. With the increase of aging time, oil stains gradually deteriorated because of oxidation and decay, so the influence of oil stains on the durability of paper is greater in the early stage than in the later stage of aging.

Abstract:Ancient Chinese paintings and calligraphy boast a long history, but many diseases occur in very old collections. Consequently, traditional restoration techniques for paintings and calligraphy have been developing. Based on experience, observing and analyzing diseases is an important precondition to developing a restoration plan. But the shedding of pigment is a secondary disease occurring during restoration. It is often overlooked during planning, which may then cause the destruction of painting, loss of color and dimming, and even the loss of parts of content. The disease is extremely harmful to paintings, so it is important to research the secondary shedding of pigment during restoration and optimize related restoration techniques. Based on practical experience, we carefully researched the secondary shedding of pigment during restoration, analyzed its cause from the perspective of materials and techniques, and proposed criteria for its prevention. This work could provide reference for the research on diseases of ancient paintings and calligraphy as well as the optimization of restoration techniques.

Abstract:The application of chemical plating and brush plating technology to the restoration of gilded copper objects was studied using scanning electron microscopy (SEM), X-ray diffraction (XRD) and other testing methods. It was found that the plating effect was good. After these studies, a series of conservation and restoration methods including stubble cleaning, filling, chemical plating, brush plating, corrosion inhibition and sealing were carried out on a defective gilded copper object, and the preparation of an independent accessory was also fulfilled. After the restoration, the object was complete in shape and harmonious in appearance, reproducing its aesthetic value.

Abstract:Coating measures are of great significance to the conservation and restoration of cultural relics. Coating protection can effectively block the impact of environmental factors (moisture, oxygen, air pollutants) on cultural relics and improve their resistance to corrosion. At present, acrylic resin B72 and silicone are widely used in the field of cultural relic conservation. They have significant effects on the conservation of cultural relics in collections, but their UV resistance is not good and cannot well meet the requirements of long-term conservation of outdoor cultural relics. In recent years, fluorocarbon materials have gradually attracted the attention of cultural relic conservators due to their excellent weather and aging resistance. In our study, we selected a new type of fluorocarbon material—F2311 fluoroelastomer—as the research object. Recently, there have been reports on the application of fluoroelastomers to the conservation of cultural relics such as metal, pottery, and polychrome ones, as well as murals, but the reports mostly focus on applications; that is, there are few studies to verify or investigate the conservation effects of fluoroelastomers from a theoretical perspective. In order to determine the resistance to aging of a fluoroelastomer and its applicability in the field of cultural relic conservation, the F2311 fluoroelastomer, the acrylic resin B72 and two kinds of silicone coatings (TEOS and industrial product KSE-OH300), were selected for a performance comparison study. They were tested for long-term aging through accelerated ultraviolet aging experiments, and their structure and performance were characterized in terms of infrared spectra, contact angles and color differences. The results show that:1) the fluoroelastomer F2311 had excellent UV resistance, and its color, structure and hydrophobic property did not change significantly under the action of long-term ultraviolet irradiation. It is speculated that this fluoroelastomer can be used for long-term outdoor or indoor cultural relic conservation, especially in complex storage environments; 2) B72 underwent oxidative degradation under ultraviolet irradiation and this degradation reaction started at the beginning of ultraviolet irradiation, which was proved by corresponding infrared spectra. The oxidative degradation of B72 under ultraviolet light led to the yellowing of the sealing film and caused color differences on the surface of cultural relics. It is speculated that B72 is not suitable for long-term conservation of outdoor cultural relics; 3) the hydrophobic properties of the two kinds of silicone materials were average after film formation, the structures were prone to becoming unstable under ultraviolet radiation, and they also became yellow. It is speculated that these two kinds of silicones are also not suitable for long-term conservation of outdoor cultural relics.  This study evaluated the UV resistance of the materials to investigate their aging resistance and their applicability in the field of cultural relic conservation. The results indicate that the new coating material, the fluoroelastomer F2311, has better UV resistance than B72 and the two kinds of silicones. This work could provide references for the selection of coating materials for cultural relics.

Abstract:Gangwa kiln is a large-scale kiln of the Liao Dynasty in Inner Mongolia. It is an official kiln of the Liao Dynasty and is in the same historical period as Ding kiln, one of the five famous kilns in the Song Dynasty. In order to reveal the relationship between Gangwa kiln and Ding kiln in terms of the body, glaze and crafts of porcelains, our study analyzed the chemical compositions of the body and glaze of white porcelains of the two kilns using energy dispersive X-ray fluorescence spectrometry (EDXRF), and also analyzed their microstructures and firing temperatures. With the aid of previous research data, we systematically compared the chemical compositions of the body and glaze of white porcelains and the crafts of Ding and Gangwa kilns. The results show that Gangwa kiln was largely affected by Ding kiln, and that the production of white porcelains in Gangwa kiln reflected the exchange of porcelain-making techniques between the Song and Liao Dynasties.

Abstract:As the earliest artificial building materials, burnt clay products led to a fundamental improvement in the living environment of prehistoric human beings. There are many viewpoints on the causes of burnt clay buildings, such as artificial baking, accidental fire, and abandonment customs, etc. Determination of the firing temperatures of burnt clay materials in prehistoric architectural relics is helpful by providing important information on technical development and enriching research on the history of prehistoric buildings.  Magnetic research shows that soil and other sediments at archaeological sites contain newly-formed magnetite, maghemite and other strongly magnetic minerals after being heated, resulting in significant enhancement of magnetism, and that the mineral compositions and magnetism hardly change thereafter.However, when the re-firing temperature is close to or greater than the original firing temperature, the destruction of original minerals or the formation of new minerals in samples causes a change in mineral magnetism. As a result, analysis in the laboratory of the characteristics of magnetic susceptibility variation of heated clay with temperature changes can reflect the firing temperatures of burnt clay products. Sujiacun site is an important settlement site from the late Dawenkou culture to the early middle Longshan culture. The fifth layer is a burnt clay layer with a thickness of about 20—40 cm that covers the whole site. It is speculated that the layer is a construction waste accumulation site or a man-made accumulation site caused by house collapse. In this study, the compositions, structural characteristics and firing temperatures of burned clay samples unearthed from Sujiacun site were analyzed by X-ray diffraction (XRD), X-ray fluorescence spectrometry (XRF) and magnetic susceptibility method. The results show that the white clay (kaolin) raw material was artificially added to the white ash layer of the burnt clay samples from the Sujiacun site, and that plant debris was intentionally added as an extender to the burnt clay layer. It is speculated that this is straw-reinforced mud used to improve the strength and adhesion of the body. This verifies the speculation that the samples may come from building materials. The burnt clay samples were artificially fired, with the firing temperatures ranging from 600 ℃ to 700 ℃. There is no vitrification inside the burnt clay, the structure is loose and the compressive strength is low. When formulating a scheme for protection of burnt clay relics, we should take targeted protection measures according to the firing temperatures of burnt clay in order to achieve the best protection effect. The appearance of burnt clay products brought humans into a new level of skill in building houses. The study of burnt clay products is of great significance to understanding the architectural technology of the late Neolithic Age in Shandong Province. The magnetic susceptibility method is suitable for studying the firing temperatures of low-temperature-fired burnt clay samples and could be further applied to the study of the firing temperatures of early pottery (especially low-temperature pottery).

Abstract:Aggregation and crystallization of soluble salts is a critical contributor to the surface weathering, structural deconstruction and loss of strength of ancient bricks of the Great Wild Goose Pagoda in Xi’an, Shaanxi Province. In order to analyze the mechanism of the salt disease, we carried out a deterioration simulation where brick samples from the pagoda were soaked with a saturated solution of sodium sulfate. During the repeated cycles of crystallization-dissolution of thenardite (sodium sulfate), we determined the variation of mass, wave velocity, uniaxial compressive strength and other characteristics of the samples. The results show that 1) the weathering phenomena of the samples in the laboratory were similar to those of the natural bricks of the pagoda; 2) the continuous crystallization force of thenardite increased the porosity and loosened the inner structure of the bricks; 3) the variation patterns of mass, wave velocity and uniaxial compressive strength were similar—increasing at the beginning and then decreasing. The bearing capacity of a brick for soluble salts is 0.5% that of the mass percentage.

Abstract:Among Dunhuang murals, the architectural images on the north wall of Cave 172 of Mogao Grottoes are the most typical representatives of the architectural styles of the glorious age of the Tang Dynasty. Aiming to explore the 3D digital rendering of 2D architectural images of Dunhuang murals, we took the central Qiandian image on the north wall of Cave 172 of Mogao Grottoes as an example, in combination with historical literature and empirical materials, to conduct a speculative study, although based on limited data and logical structures. In addition, the integrated application of digital image-processing software (Adobe PhotoShop, Adobe Illustrator) and 3D modeling software (SketchUp, Rhino) helped establish a 3D color model of the central Qiandian, realizing the virtual transformation of architectural images of murals from 2D to 3D, reproducing the architectural images of murals in a relatively scientific and objective way. Through 3D printing and other rapid prototyping technology, and virtual projection screen and other means of display and utilization, the value of technical achievements is deeply explored, the value interpretation and display depth of mural heritages is extended, and the surreal space experience is brought to the viewers.

Abstract:Recent studies of bacterial corrosion of cultural relics in seawater have mainly focused on deep-sea salty cement and light cement. However, there are few reports on corrosive bacteria in zones of mixing of fresh and salt water. Estuarine and coastal waters are rich in underwater cultural relics and the interaction of salt and fresh water affects the burial environment and cultural relics. In our study, muddy marine samples were collected at different levels of the sea bed near the No.Ⅱ shipwreck at the North Channel of the Yangtze Estuary, and 18 strains of bacteria were isolated using non-directional enrichment medium. Four corrosive bacteria were identified by 16S rDNA sequence analysis:Shewanella hafniensis, Bacillus wiedmannii, Exiguobacterium aquaticum and Exiguobacterium indicum. First, the isolated bacteria were cultured, until they reached their logarithmic growth periods, in a 30 ℃ shaker at a rotational speed of 220 r/min, and then they were allowed to act upon porcelain, pottery, wood and other common cultural relic materials. After a 7-day incubation, those cultural relic materials were sprayed with gold,dried and then observed using scanning electron microscopy (SEM). Biofilms are closely related to the occurrence of microbial corrosion. In addition to the reported corrosive strains, we also found two previously-unreported bacteria—Shewanella xiamenensis and Aeromonas hydrophila—that also produce biofilms on the surface of materials. The experimental results provide scientific reference for explaining the burial environment of cultural relics in the mixture area of fresh water and salt water at estuarine and coastal areas and better understanding of cultural relic conservation. Compared with previous literature, our study expands in the following three aspects:1) the corrosion phenomena of corrosive bacteria on porcelain, pottery and wood cultural relic materials were studied, and the formation of biofilms closely related to microbial corrosion was observed, so as to demonstrate the corrosive effects of Shewanella hafniensis, Bacillus wiedmannii, Exiguobacterium aquaticum and Exiguobacterium indicum on porcelain, pottery and wood materials; 2) two previously-unreported corrosive bacteria-Shewanella xiamenensis and Aeromonas hydrophila, which can also form biofilms on the surface of materials-were found for the first time, preliminarily indicating that these two bacteria also have potential corrosive effects; 3) Bacillus was explored as the dominant strain in the zone of mixing of fresh water and salt water in the Yangtze Estuary, further revealing the richness of the marine bacterial library because more corrosive bacteria (different from sulfate-reducing bacteria) were found in our study.  This study focuses on the relationship between corrosive bacteria abounding in the zone of mixing of fresh water and salt water in the Yangtze Estuary and the corrosion of porcelain, pottery and wood cultural relics, which, to some extent, lays a foundation for the study of corrosive bacteria in the waters. It is conducive to the following application to cultural relic conservation and other related aspects.

Abstract:Shuilu Temple is located at the foot of Wangshun Mountain in Lantian County, Shaanxi Province. In the temple, there are more than 300 m² of exquisite Ming Dynasty painted clay sculptures, the most complete clay sculpture collection in China. In order to clarify the use of pigments in Shuilu Temple’s painted clay sculptures, optical microscopy (OM), X-ray diffraction (XRD), microscopic infrared spectrometry, micro-Raman spectrometry and scanning electron microscopy with energy-dispersive spectrometry (SEM-EDS) were used to scientifically analyze pigment samples. The results show that, except for the blue pigment (Prussian blue) in the remake area on the back of the partition wall, most of the pigments used for painted sculptures in Shuilu Temple are mineral pigments, including lead red, cinnabar, iron red, atacamite, orpiment, mica, etc. These results provide a scientific basis for the subsequent conservation and restoration of Shuilu Temple, as well as supplementing scientific information to enrich knowledge of pigment types of Ming Dynasty painted clay sculptures in Guanzhong area.

Abstract:Having great historical, scientific and artistic research value, the archaeologically unearthed Terracotta Warriors of the first emperor of the Qin Dynasty are very precious physical materials of the Qin Dynasty. Their representation of “thousands of people with thousands of faces” has attracted much attention and is considered to be a true portrayal of Qin people. In modern anthropometry, head and face features are widely used to analyze the genetic relationship between ethnic groups because they are primarily affected by genetic factors rather than environmental factors. We collected high-precision 3D point cloud data from the heads of 50 samples of Terracotta Warriors and extracted their head and face features. Using the methods of sample correlation analysis and data size-sorting statistical analysis, we compared these results with the head and face features of 29 modern groups or areas. The results show that the head and face features of the Terracotta Warriors are completely different and highly correlated, and have little difference with those of modern nationalities, quantitatively defining the relevant features of Terracotta Warriors.

Abstract:Based on the analysis of microenvironment monitoring data of Cave 128 of Bingling Temple Grottoes, and the statistics of visitors in 2019, we investigated the influence of tourist volume on the microenvironment of Cave 128. The results show that the CO₂ concentration of Cave 128 was positively correlated with the tourist volume, and its rate of reduction was positively correlated with the temperature difference between the inside and outside of the cave. The cave temperature was positively correlated with the tourist volume to a certain extent. The temperature increment was mainly positive, and the negative values were related to the meteorological conditions outside. The temperature reduction was positively correlated with the temperature increment and temperature difference between the inside and outside of the cave. Changes of relative humidity of Cave 128 were more complicated. By this analysis, the influence of tourist volume on relative humidity was in the range of -5%~10%, mostly causing the reduction. According to the results, the current opening mode is conducive to the diffusion and reduction of CO₂, so the number of visitors per batch could be appropriately expanded to 10, in order to cope with situations where there are large numbers of visitors. It is vital to monitor the relative humidity changes during peak tourist seasons, especially in May, and from late September to middle October, and also to improve the management of tourists and control of the cave relative humidity. This research has certain guiding significance for the tourism opening management of Cave 128 and other similar caves of Bingling Temple Grottoes.

Abstract:The conservation of cultural relics in a “sci-tech” way in China started in the early 1950s and has followed the development of China’s social economy, science and technology. Guided by many challenges faced by the conservation of cultural relics and their preservation in the environment of open display, this new trend focuses on basic research, and the development of technology and equipment for conservation, as well as research on conservation systems and standards. A number of scientific and technological breakthroughs have been made in the construction of conservation technology platforms, resulting in a series of achievements. This paper focuses on the achievements of scientific and technological innovation in the field of cultural relic conservation and also discusses the developmental trends of cultural relic science and technology in China. The results show that the scientific research on the conservation of cultural relics in China has changed 1) from working behind closed doors and fighting separately for resources, to cooperating mutually, refining commonalities and overcoming difficulties; 2) from randomness to standardization, thereby establishing a common discourse system; 3) into becoming problem-oriented, with the supporting roles becoming more and more obvious; 4) in that attention is paid to both rescue and preventive conservation, rather than the former only. The goals of making systematic breakthroughs in theory, technology, equipment and standard construction, etc. have been basically realized.

Abstract:Due to natural factors and human activities, ancient murals, stone carvings and other precious cultural heritages tend to suffer from widespread diseases such as disruption, salt efflorescence crusting, powdering, weathering, sootiness and pollution. The research and development of corresponding conservation and restoration materials and technology has long been a focus in the field of cultural relic protection. In recent years, bio-nano materials and biotechnology have become supplemental or alternative measures to conventional physical and chemical counterparts due to their superiority with regard to environmental friendliness, compatibility and applicability, and better conservation effects. This study systematically summarizes and sorts out the development context and state of application of functional microorganisms, biological enzymes, metabolites and innovative biotechnology with regard to the conservation and restoration of cultural heritages. These studies focus mainly on the latest research progress, as well as challenges of biological cleaning and reinforcement technology. They provide reference for scientific researchers to carry out innovative research on the conservation and restoration of cultural relics based on biotechnology.