Performance Evaluation of Commercial Nanolime as a Consolidant for Friable Lime Based Plaster
Historic Preservation and Conservation
This thesis focuses on the performance evaluation of commercial nanolime as a consolidant for friable historic lime based plaster such as found at Mission San Jose de Tumacácori, a Spanish Colonial mission site near Tucson, Arizona. The church’s façade was originally finished with a polychromatic painted on fired brick and adobe. Though generally stable over time, the exterior plaster at Tumacácori became friable and detached after repeated weathering cycles of high diurnal temperature swings and precipitation concentration during monsoon season in the summer. As friable stucco is vulnerable to loss, consolidation should be considered a first priority in the conservation plan for the Tumacácori’s façade. Derived from an older limewater method, nanolime is a relatively recent material created by synthesizing nanoscale calcium hydroxide particles and obtaining stability through using alcohol solvents. CaLoSiL®, produced by IBZ-Salzchemie GmbH&Co. KG, was selected for performance testing as a consolidant for friable plaster studying its effect on enhancing grain cohesion, durability to weathering, and impact on aesthetic character. ASTM and RILEM testing methods were employed including splitting tensile strength, porosity by liquid nitrogen immersion, water vapor permeability, color change, frost resistance, and optical and scanning electron microscopy. Ultimately, the analytical findings of this thesis will be used as a recommendation for future conservation of the Tumacácori façade.