Preparation of Highly Crystalline Nano Ca(OH)2 and Its Comparative Assessment with Commonly Used Materials for the Protection of Wall Paintings

Abstract

AbstractDue to the ecocompatibility with carbonate‐based substrates, Ca(OH)2 nanoparticles are currently used for cultural heritage conservation such as wall paintings. However, the nano Ca(OH)2 still suffers from different forms and poor uniformity, limiting its application potential. Also, there is a lack of systematic comparative studies between nano Ca(OH)2 and the commonly used wall painting reinforcement materials. In this study, homogeneous hexagonal nano Ca(OH)2 particles with a size of ≈100 nm are successfully prepared through the convenient chemical liquid phase method and by utilizing surfactants to control the growth. The resulting nano Ca(OH)2 is less agglomerated and has superior crystalline morphology, prolonged suspension time, and more suitable carbonation time in comparison to commercial Ca(OH)2 materials. Additionally, the reinforcement effect of the resulting nano‐Ca(OH)2 with that of the commonly used pigment layer reinforcement materials such as AC33, B72, Tetraethyl orthosilicate, WPU (Waterborne polyurethane) and commercial Ca(OH)2 is systematically compared. The synthesized nano Ca(OH)2 penetrated wall painting blocks to a depth of 683 µm, three times deeper than commercial Ca(OH)2, achieving moderate color deviation, higher flexural strength (0.529 MPa), and bond strength (1.105 mg cm−2), thus highlighting its potential in wall painting reinforcement and expanding its application scope.