Conservation of surface gypsification stone relics using methanol solution of barium hydroxide as a novel treating agent

The conservation of surface gypsification stone relics using methanol solution of barium hydroxide as a novel treating agent was studied. In application, the methanol solution of barium hydroxide and water was introduced into the gypsum crust successively, and the gypsum crust was converted into protective barium sulfate and calcium carbonate layer. The conservation effect of barium hydroxide methanol solution was investigated by Raman spectroscopy (RS), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffractometry (XRD), water solubility, color difference, capillary water absorption and surface hardness. The results indicated that the methanol solution of barium hydroxide could obtain a good permeability in gypsum crust. Hence, the desulfuration procedure in the traditional barium hydroxide method was not necessary anymore. After treatment by the methanol solution of barium hydroxide, the water solubility of the specimens was significantly decreased, and the surface hardness was significantly increased. In addition, the inherent physical properties of gypsum crust such as pore structure and original appearance were almost unaffected. Therefore, the methanol solution of barium hydroxide would be promising for the conservation of surface gypsification stone relics.