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Thermal and Hygroscopic Characteristics of Restored Plasters with Different Surface Textures

Fresco restoration includes the integration of missing plaster. Restorers use different tools and materials for the intervention. Recent research shows that restored plasters have different thermo-hygrometrical behaviors at low temperature and high ambient humidity rate. Field observations of the hygroscopic behavior of different mortar textures showed that textures obtained with hard tools (spatula, wooden float, trowel) have harder, denser surfaces, which favor vapor condensation, while soft tooled finishes (sponge, sponge float) have a rough surface that facilitates absorption and evaporation of moisture. In case of contiguity between two different finishes, the edges of the rougher surface (around a more compact texture) show more damage than the smoother and compact surface. Despite chemical compatibility of mortar compounds, the effect of changes in waterstateon the surfaces causes differential damage, starting from the edge of replastered areas. The durability of plasters applied with different tools, resulting in heterogeneous textures, can be shorter than that of homogeneous textures. Early detection of risk areas, by means of infrared thermography at transient conditions, is very helpful for the preservation of historical buildings without a controlled heating/cooling system, and it offers an improvement in restoration techniques of precious surfaces.

References
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