Mural Deterioration Research Articles

Assessing the carrying capacity for the environmental protection of the ancient artworks of India’s Ajanta caves

Purpose The purpose of this study is to investigate environmental factors impacting Ajanta mural deterioration, assessing global tourism effects and visitor conduct on cave environment and murals. This study recognizes stakeholder roles in conservation, providing data-driven insights to guide institutions like the Archaeological Survey of India. The objective is sustainable tourism practices to balance public access with mural preservation for future generations. Design/methodology/approach Over 25 years, Ajanta Caves' visitors doubled, impacting microclimatic conditions for ancient murals. This study assesses visitor impact to establish a regime and determine carrying capacity, considering temperature, humidity and pollution. Challenges arise from quantifying capacity because of variables. This research informs global tourism and heritage conservation, offering methodologies applicable to cultural sites worldwide. Findings This study examines environmental impacts on mural preservation in Ajanta Caves, including humidity, microbial growth, sunlight exposure, air quality and tourist presence. Tourist influx escalates CO2 levels, directly endangering murals. Concerns about particulate matter, especially during visits, emphasize the need for data-driven decision-making and modern technology use to protect Ajanta Caves' artwork, crucial because of its global significance and tourism-related vulnerabilities. Social implications This study carries substantial social implications with a global resonance. The active engagement of the local community and tourism stakeholders in conserving and promoting the Ajanta Caves fosters empowerment, igniting a sense of pride, ownership and responsibility among residents and ensuring sustainable enjoyment of cultural heritage while safeguarding it for future generations. In addition, there will be socioeconomic benefits to local residents such as employment opportunities as tour operators, tour guides, hospitality staff, artisans and souvenir shopkeepers. Originality/value This study integrates art conservation, environmental science, cultural heritage preservation and social aspects to address global tourism challenges. Focusing on a site of worldwide significance, this study offers practical strategies for artwork preservation, tourism management and environmental concerns. These recommendations provide real-world solutions applicable to heritage sites globally, bridging scientific analysis with social and cultural insights.

The influence of different clay/sand ratios on the hygrothermal properties of earthen plasters in the Maijishan Grottoes

Variations in temperature and moisture content in the earthen plasters of the Maijishan Grottoes can readily lead to mural deterioration. This study investigates the influence of two different clay/sand ratios on the hygrothermal properties of earthen plasters in the Maijishan Grottoes. Two distinct types of earthen plasters samples were created with different clay/sand ratios: one with a weight ratio of 30:70 and another with a weight ratio of 70:30. The hygrothermal properties of earthen plasters samples were examined, and the temperature and moisture content variations were evaluated based on measurement data of hygrothermal environment in three caves. The findings revealed that the influence of the clay/sand ratios on thermal properties was relatively minor compared to its effect on hygric properties. Lower clay/sand ratio resulted in decreased thermal conductivity and specific heat capacity of earthen plasters, leading to increased temperature fluctuation, but the difference is minor. Additionally, in high-humidity environments, the difference in moisture content variations between the two types is greater than in low-humidity environments as the relative humidity changes. This research holds significant implications for the preservation of murals in the Maijishan Grottoes while also providing fresh perspectives for the restoration of multi-layered mural structures.

Rainfall influence and risk analysis on the mural deterioration of Dunhuang Mogao Grottoes, China

The Dunhuang Mogao Grottoes are a significant cultural heritage site in the Silk Road, famous for its wonderful murals and statues. The rainfall causes the changes of humidity in the caves, which can easily activate the salts diseases of murals. In order to prevent the deterioration of the murals, the environmental monitoring tests were conducted to analyze the microclimate changes of the cave in rainfall weather, and proposed the risk prevention measures and suggestions. The results indicate that the temperature of caves has small change, but the humidity shows a clear trend of increase. The humidity and the duration of high humidity increases with the increase of the rainfall grade and frequency. The optimal starting time for environment control in the cave is when aatm and acave are consistent, and the relative humidity is controlled below 62%. The caves with lower layer, larger degree of openness and small volume are most vulnerable to water vapour diffusion. The environment monitoring should pay more attention to the continuous rainfall weather and the vulnerable caves. The research has great significance for the prevention of ancient mural deterioration.

Spatial and temporal changes in microclimate affect disease distribution in two ancient tombs of Southern Tang Dynasty

Two tombs of the Southern Tang Dynasty (Qinling Tomb and Shunling Tomb), the most important cultural heritages in China, were built for emperors 1000 years ago and decorated with murals and stone sculptures. After their excavation in the 1950s, it was found that drastic fluctuations in the environment within the tombs had caused multiple diseases, such as salt efflorescence, powdering, and biodeterioration, which led to irreversible damage to the murals. This research comprised long-term (yearly) environmental monitoring and short-term (monthly) investigation into the distribution of salt crystallization and microbial growth within the two tombs. The objective was to unveil the relationship between the temporal and spatial distributions of the mural diseases and environmental characteristics while proposing a promising environmental regulation strategy for relic conservation. The results showed a gradual reduction in temperature fluctuation from the entrance to the back chamber and a distinct vertical stratification in relative humidity. The relative humidity in the upper areas of the tombs reached 100% during summer, while it averaged around 40–50% in the lower areas during winter. Consequently, significant condensation was observed on the ceiling in summer, whereas salt crystallization occurred on the murals in the lower space in winter. The distribution of these diseases was influenced by the airflow exchange between the interior and exterior. Furthermore, the structural disparities between the two tombs contributed to higher relative humidity and greater microorganism coverage in the Shunling Tomb compared to the Qinling Tomb. From the abovementioned findings, we suggest that microclimate control is essential for mitigating mural deterioration and should be paid more attention in the future.

Automatic calibration of crack and flaking diseases in ancient temple murals

Many precious ancient murals are seriously deteriorated due to long-term environmental influences and man-made destructions. How to effectively protect ancient murals and restore these murals’ original appearance has become an urgent problem for field experts. Modern computer technology makes it possible to virtually restore the deteriorated areas in ancient murals. However, most existing mural restoration approaches require manual calibration of the deteriorated areas, which is very difficult and time-consuming. It has been noticed that the earth layer flaking and cracks are the most common problems of ancient temple murals. This paper proposes an automatic calibration method for the earth layer flaking and cracking deterioration of murals by taking temple murals from the Ming Dynasty in Zhilin Temple as the study object. First, we extract the texture and line features of the deteriorated murals by using multi-dimensional gradient detection in the HSV space. Then, a guided filter operation is employed to highlight the disease (deteriorated) areas and meanwhile suppress other unwanted areas, which helps to extract the flaked areas or cracked lines from the digital murals. The filtered images are segmented by using an automatic threshold to obtain the initial masks of the mural disease areas. Next, we use a two-dimensional tensor voting technique to connect the discontinuous edge curves of the extracted disease areas. Afterwards, the masks of flaking and cracking areas can be generated after morphological processing. Finally, we obtained the calibration results by adding the masks to the original digital murals. Experimental results show that our method can rapidly and accurately calibrate the cracks and the earth layer flaking diseases in the ancient murals. As compared to existing calibration approaches, our method can achieve better performance in subjective visual quality and objective evaluation metrics. Moreover, the method does not need human-computer interaction. This research work provides a solid foundation for the following virtual and practical restoration of ancient murals.

Modeling and numerical simulation of heat and mass transfer in the cave wall of the Mogao Grottoes in China

In the Mogao Grottoes in Dunhuang, China, temperature and relative humidity (RH) fluctuations are the main causes of the observed deterioration. In this paper, we experimentally and numerically analyze hygrothermal transfer in the cave wall of the Mogao Grottoes. A coupled heat and moisture transfer 1D model is developed to simulate the hygrothermal behavior of the cave wall of the Mogao Grottoes, which adopts the temperature and water vapor pressure as driving potentials. The model is implemented in a programming. By constructing the numerical model of the wall under boundary conditions and comparing the measured data and simulation results, we validate the numerical model and analyze the hygrothermal transfer characteristics of the wall. The temperature and moisture profiles of the cave wall are experimentally measured and numerically determined. The simulation results are compared to experimental temperature and RH values, with good agreement despite the simplifying hypotheses adopted during modeling. By analyzing the heat and moisture distributions, we find that the heat and moisture transfer process in the cave wall changes in space and time. The complicated heat and moisture transfer directions vary cyclically. Additionally, moisture transfer in the cave wall reaches the steady state more rapidly than heat transfer. Hygrothermal cycling plays an essential role in the development of mural deterioration. The developed model provides theoretical support and a scientific method for the conservation of cave sites and a quantitative analysis approach to study mural relics.

Learning to grade deterioration for ancient murals

Ancient murals recording histories and myths are suffering different types of deteriorations, which makes these valuable cultural heritage unrecoverable. For preventive protection of ancient murals, the researchers need to rate the grade of the mural deteriorations. However, the present grading is mainly rely on the experience of the cultural relics’ protection staff. In this paper, we propose to learn a mural deterioration grading network (MDGN) for generating robust and accurate mural deterioration grading. MDGN has similar architecture with AlexNet but with less network parameters. We built two small mural deterioration grading datasets on briquettes and real grottoes. We use image patches to generate enough training samples for MDGN. Dense pixel-level grading can be obtained by the means of sliding window. Extensive experiments on simulated data and real murals verify the effectiveness of the proposed ancient mural deterioration grading method. Our method achieves superior grading results on both quantitative and qualitative comparisons with baseline.

Extraction of Hidden Information under Sootiness on Murals Based on Hyperspectral Image Enhancement

Changes in the environment and human activities can cause serious deterioration of murals. Hyperspectral imaging technology can observe murals in the range of visible to near infrared light, providing a scientific and non-destructive way for mural digital preservation. An effective method to extract hidden information from the sootiness of murals in order to enhance the visual value of patterns in ancient murals using hyperspectral imaging is proposed in this paper. Firstly, Minimum Noise Fraction transform was applied to reduce sootiness features in the background of the mural. Secondly, analysis of spectral characteristics and image subtraction were used to achieve feature enhancement of the murals. Finally, density slicing was performed to extract the patterns under the sootiness. The results showed that the extraction of hidden information was achieved with an overall accuracy of 88.97%.

Improved region growing algorithm for the calibration of flaking deterioration in ancient temple murals

Ancient murals are vulnerable to varying degrees of damage due to long-term exposure to external environmental factors such as light, temperature and humidity. Enabling people to appreciate the original features of murals has become a concern for field experts. The development of computer technology makes it possible to use intelligent information processing to simulate and restore ancient murals. This paper proposes an improved region growing algorithm based on threshold segmentation to automatically calibrate the flaking-related deterioration of murals in response to erosion by taking temple murals from the Song Dynasty in Kaihua Temple as the study object. First, we analyze the color characteristics of the flaking area, mark the suspected flaking-damaged points by threshold segmentation, and use these points as seeds for the area growth and expansion of the flaking area. We then calculate the color mask. Next, in the YCbCr and HSV color spaces, the brightness, chroma, and saturation characteristics of the flaking area are analyzed. The masks for the brightness, chroma, and saturation of the flaking area are obtained by threshold segmentation, and all the feature masks are merged. Finally, the mask of the flaking area obtained by data fusion is added to the original image to calibrate the flaking deterioration. Compared with current calibration algorithms based on multiscale mural deterioration, the experimental results show that the average error and error standard deviation of the proposed calibration algorithm are 1.91 and 1.82, respectively, without noise and 1.97 and 1.85, respectively, with noise. The errors are reduced, and the calibration performance is improved and stable. This work provides a good foundation for the virtual and practical restoration of ancient murals.

Biodegradative potential of fungal isolates from sacral ambient: In vitro study as risk assessment implication for the conservation of wall paintings.

The principal purpose of the study was to evaluate in vitro the potential ability of fungal isolates obtained from the painted layer of frescoes and surrounding air to induce symptoms of fresco deterioration, associated with their growth and metabolism, so that the risk of such deterioration can be precisely assessed and appropriate conservation treatments formulated. Biodegradative properties of the tested microfungi were qualitatively characterized through the use of a set of special agar plates: CaCO3 glucose agar (calcite dissolution), casein nutrient agar (casein hydrolysis), Czapek-Dox minimal medium (pigment secretion); and Czapek-Dox minimal broth (acid and alkali production). Most of the tested isolates (71.05%) demonstrated at least one of the degradative properties, with Penicillium bilaiae as the most potent, since it tested positive in all four. The remaining isolates (28.95%) showed no deterioration capabilities and were hence considered unlikely to partake in the complex process of fungal deterioration of murals via the tested mechanisms. The obtained results clearly indicate that utilization of fast and simple plate assays can provide insight into the biodegradative potential of deteriogenic fungi and allow for their separation from allochthonous transients, a prerequisite for precise assessment of the amount of risk posed by a thriving mycobiota to mural paintings.

Learning multi-path CNN for mural deterioration detection

Mural deterioration easily destroys valuable paintings and must be monitored frequently for preventive protection. Deterioration detection in mural images is often manually labeled and is a preprocessing step for mural protection and restoration. Many deterioration forms are commonly invisible with only one lighting condition because mural deterioration is caused by changes in the material and plaster layer. This study addresses mural deterioration detection through a multi-path convolutional neural network (CNN), which takes images of a scene with multiple lightings as inputs and generates a binary map that indicates deterioration regions. We design an eight-path CNN in which seven paths are utilized for basic feature extraction from lighted images, and the remaining path is responsible for cross feature fusion. This mechanism enables our method to not only identify suitable features for different lightings but also utilize these features collaboratively through cross feature fusion. Furthermore, we build two realistic mural deterioration datasets of real-world mural deterioration and briquettes that simulate the cave deterioration. Extensive experiments verify the effectiveness and efficiency of our method.

A non-destructive approach using MatLab software for morphology analysis of ancient mural deterioration

The murals in Dunhuang Grottoes, a famous world cultural heritage site, are precious and unique, so research on mural surface changes and evaluation of the degree of deterioration should be non-destructive. In this study, tracking photographs of a simulated mural surface were processed with MatLab software to obtain a three-dimensional image and Z axis data, and a calculation method for quantitative analysis was also proposed. The feasibility of this approach was confirmed by simulated experiments of mural damage in the laboratory and analysis of real murals in situ. It was also applied to analysis of surface deterioration of an earthen archaeological site before and after rainfall erosion. As a simple and non-destructive approach, it could be used for the analysis of micro changes in murals or for monitoring real time surface changes at cultural heritage sites.

Ammonia chemistry within Danish churches

The increase of agricultural intensity over the last century in rural Denmark has meant that ammonia has been regarded as a significant environmental problem. The deterioration of murals in rural churches is also a matter of concern and focused attention on the potential for ammonia to accelerate damage. Ammonia concentrations measured over 12months inside and outside nine churches often show a spring maximum outdoors, hinting at the importance of farming activities. The ammonia concentrations are on average some three times greater indoors than outdoors and mass balance calculations suggest that this arises from the decomposition of ammonium nitrate aerosols. The emissions may result from reactions of aerosols deposited at the alkaline walls, which also leads to calcium nitrate becoming the major soluble salt at the very surface layer. The quantities remain small enough, that they probably do not participate in salt damage to the murals.

The X-ray photoelectron spectroscopy of ancient murals in the tombs at Beni Hasan, Egypt

The once colourful mural paintings at the Beni Hasan tombs (ca. 2100 B.C.), an important Egyptian archaeological site, are covered with an obscuring grey deposit. Qualitative observations made over the past 150 years were assembled and correlated with each other by us. Cumulatively, they indicate that recently the development of this layer has accelerated. To study this surface degradation, X-ray photoelectron spectra of fragments from the painted walls have been collected. Empirical XPS sensitivity factors have been employed to treat the data semiquantitatively. Three types of surfaces were identified. The first surface consists of CaCO3 and SiO2 as major constituents, and was the only surface identified previously. Our XPS data indicate that it also contains Al2O3, NaCl, MgO, sulphates, and phosphates as minor and trace components. The second surface consists predominantly of aluminium silicates. The third surface consists mostly of calcium carbonate. A preliminary mechanism for opaque layer formation is proposed herein. It suggests that the principal physicochemical processes are adsorption of water in the presence of carbon dioxide, followed by dissolution of the substrate walls upon which the murals were painted. This mechanism is consistent with our finding that mural deterioration is recent; it also indicates that deterioration is progressive, continuous, and cumulative. Further experiments are designed to verify the proposed mechanism. Two mechanisms proposed earlier are found to be inconsistent with at least some of our findings. Relatively recent efforts in removing obtrusive surface layers with dilute HCl were found to be performed carefully; there was no evidence of excess chlorides on cleaned surfaces. However, this finding does not provide a guarantee that murals were undamaged by HCl below the surface. It does suggest that progressive damage due to the formation of hygroscopic CaCl2 on the surface has been avoided.