2022 is the Asian Games year and the competition will be held in Hangzhou! The members of ZJU-China enthusiastically engaged in this global sporting event, hoping to share the story of Hangzhou with friends from afar.
Hangzhou, known as "paradise on earth" in China, not only has beautiful natural scenery, but also has profound cultural heritage. Temple Lingyin, a famous ancient Buddhist temple in China with a history of about 2,000 years. In order to help people around the world understand the open, inclusive and diverse Hangzhou culture, we embarked on a journey to find Lingyin in May.
As we strolled around in the spring, our eyes were gradually drawn to the Maitreya Buddha statue on the other side of the temple, which was covered by greenery. Peeling off the moss on the belly of the Buddha statue, what we see is not the smooth surface of the statue, but tiny cracks.For a moment, we thought that the temples affected by the epidemic can be reopened, but will these frozen stories, these common cultural treasures of mankind, lose their original brilliance forever because of the influence of these tiny cracks? We are considering, how we can make these cultural stories seen more by people around the world？
As one of the most primitive tools and materials of mankind, stone has always played an irreplaceable role in the evolution of human civilization. The dating of human history is made with the progress of the application of stone cultural relics. From the Paleolithic Age to the Neolithic Age, the fire of human civilization unfolds slowly like a picture scroll. From Indian cliff paintings, to China's Mogao Grottoes and ancient Egyptian pyramids, stone materials accompany our lives [1].
China is one of the world's four ancient civilizations which makes it exceptionally rich in tangible cultural heritage. As of 2021, there were 56 UNESCO World Heritage sites in China, ranking first in the world [2]. A large proportion of these is stone artifacts, including the world-famous Forbidden City, the Yungang Grottoes, and the Dazu Rock Carvings. These stone artifacts are often large, difficult to move, and long-term exposure to outdoor space. Numerous stone artifacts have different degrees of cracking, weathering, corrosion, and fracture because of the ecological influence and deliberate destruction.Among them, the problems caused by tiny cracks are of great concern. Tiny cracks further expand and cause corrosion of the artifacts, harboring bacteria and increasing the risk of collapse [3]. However, the limitations of existing technology lead to the fact that people are still helpless to repair small cracks.
The importance of cultural heritage conservation is well known, but most of the time, restoration measures can only be carried out when serious deterioration occurs, which not only causes irreversible damage to the cultural relics but also is time-consuming and unsustainable, not in line with the concept of green maintenance of heritage buildings [4][5]. One of the major causes is the lack of technical resources based on the occurrence of minor cracks. Stone artifacts currently require sealing, grouting, strengthening, and bonding as their primary conservation techniques. Among them, the most commonly used grouting method cannot be used for tiny cracks. Worse still, the existing materials for repairing stone relics cannot meet the demand for repairing tiny cracks. Cultural heritage buildings of stone require careful restorative actions to maintain them as close to the original condition as possible. Traditional consolidates like lime, silicic acid is not very efficient, with low adhesion, poor penetration and flexibility [6][7]. Besides, synthetic resins plug the pores when they polymerize, thus causing water retention and internal degradation, while external coatings can peel off [8].
Perhaps more promising are the new, environmentally acceptable, biologically-based consolidates, including bioconsolidation using whole bacterial cells.
Table 1 Advantages and disadvantages of different material
And Here We Are !
Focusing on the repair of tiny cracks in stone artifacts this year, ZJU-China is dedicated to developing technologies for the integrated conservation of stone artifacts based on engineered Bacillus subtilis-induced biomineralization. Extracellular calcium carbonate precipitates are brought in for filling the tiny cracks of stone artifacts, with an extracellular scaffold system to further improve the physicochemical properties of the materials. We have also added a quorum sensing module and a biosafety module to make our materials environmentally friendly and efficient. Hopefully, Story Light will be a new technology for the integrated conservation of stone artifacts!
[1] He Haiping, Zhang Yichi.Overview of the material and classification of stone cultural relics [J].Museum Technology and Applications,2011,（00）389-394
[2] "China". whc.unesco.org. Retrieved 28 September 2021.
[3] Scheerer, S., Ortega‐Morales, O., & Gaylarde, C. (2009). Microbial deterioration of stone monuments—an updated overview. Advances in applied microbiology, 66, 97-139.
[4] Wu, Y., Li, Q., Tong, H., He, Z., Qu, J., & Zhang, B. (2021). Monitoring the Deterioration of Masonry Relics at a UNESCO World Heritage Site. Ksce Journal of Civil Engineering, 25(8), 3097-3106.
[5] Forster, A. M., Carter, K., Banfill, P. F., & Kayan, B. (2011). Green maintenance for historic masonry buildings: an emerging concept. Building Research & Information, 39(6), 654-664.
[6] Ortega-Morales, B. O., & Gaylarde, C. C. (2021). Bioconservation of historic stone buildings—An updated review. Applied Sciences, 11(12), 5695.
[7] Ortega-Morales, B. O., & Gaylarde, C. C. (2021). Bioconservation of historic stone buildings—An updated review. Applied Sciences, 11(12), 5695.
[8] Price, C. A., & Doehne, E. (2011). Stone conservation: an overview of current research.
