For a long time the conservation of archaeological artefacts has been based on the principles of compatibility and minimal intervention. This involves a series of partially unsolved problems, concerning the products used for deteriorated structures consolidation. The choice of materials depends on several factors such as: microclimatic conditions, application methods, and reaction time of products. Recently the employment of nanolime in the consolidation treatments of decorative carbonate matrix surfaces had a great development, thanks to multifunctional use in calcium standard-sized particles treatments. However, while the use of the nanostructured materials is described in several specialized papers, the information about the best conditions of applicability of the nanolime and its related potentiality for the consolidation in hypogeum environment is rarely considered. The present work is devoted to represent a case study with the aim to give useful elements in order to evaluate the application of nanolime. The funerary inscriptions coming from St. Callixtus Catacombs have been the object of the research carried out in situ and in laboratory, checking indirectly in the short run and in the long run the porosity variation in the materials. The present study intends to indicate the best suspension concentration on consolidation in relationship with hypogeum environment. 1. Introduction This work grows out from the need to develop consolidating treatments tailored for a specific archaeological structure [1] under hypogeal conditions [2]. Generically in a preventive conservation project, treatments and materials are always more frequently evaluated in order to provide two main requisites:(a)minimal impact on the original structures [3], by respecting the antique execution techniques, the customary materials, and the history of the monument [4];(b)highest durability, through the combination of complementary preventive activities, such as monitoring and adjusting environmental parameters and defining a monitoring and routine maintenance plan of the structures, together with graphic and photographic documentation, and the systematic data archiving, in order to easily compare the short-run and the long-run variations. Nanotechnologies and nanolime, as consolidating materials for architectural and stone surfaces [5], have been developed mainly in the last years, for the capability to solve several problems connected with conventional lime treatments, such as incomplete lime carbonation process, limited depth penetration, and the formation of thin white
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