New Hydrophobic Treatment for the Protection of Gypsum Artifacts

¹ Dept. Chemistry, Life Sciences and Environmental Sustainability, University of Parma, 43124 Parma
² Dept. Engineering and Architecture, University of Parma, 43124 Parma
³ Dept. Mathematical, Physical and Computer Sciences, University of Parma, 43124 Parma

^* laura.bergamonti@unipr.it

Abstract

Gypsum has been widely used in traditional and monumental architecture in many countries of the Mediterranean area; however, due to its low water resistance and low mechanical strength, it can be subject to physical, chemical and biological degradation. To improve the preservation of gypsum-based plaster artifacts, a new hybrid inorganic-organic hydrophobic treatment is proposed in this work. This treatment is based on nanometric magnesium hydroxide (Mg(OH)₂) and organically modified silica (OrMoSil), a class of materials with intermediate performances between ceramic materials and polymers. The behaviour of the product was verified both as a protective on gypsum surface, as well as a consolidant added to the mixture of gypsum-based plasters. The treatment does not alter the aesthetic appearance of the surface, as verified through colorimetric analysis. As demonstrated by capillary water absorption and static contact angle measurements, the new hydrophobic protective coating proved to be very effective. Moreover, the new treatment is effective as a consolidant, leading to an improvement of the mechanical properties and to a reduction of the depth of carbonation. The new hydrophobic nanocomposite product is therefore a promising material for the protection and consolidation of gypsum monuments and artifacts of cultural interest.