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Nanolimes: from synthesis to application

Abstract Cultural heritage objects and structures are subjected to a range of weathering processes that result in their decay and destruction. To slow weathering rates and/or mitigate their effects, several protective and consolidant materials have been used during conservation interventions. Treatments based on organic polymers and alkoxysilanes, as well as some traditional inorganic treatments such as lime water, are in many cases either incompatible and/or show limited efficacy. In recent years nanolimes, that is, dispersions of Ca(OH)2 nanoparticles in alcohol (as well as alcohol dispersions of other alkaline-earth metal hydroxide nanoparticles), have emerged as an effective and compatible conservation material. Here we review recent advances in the synthesis and application of nanolimes in the field of heritage conservation. First, we present an overview of lime-based conservation materials, with an emphasis on the earliest reports on the use of nanolimes. Subsequently, we present the different methods used to synthesize nanolimes. Afterwards, we describe their carbonation and its consolidation effects. Practical application of nanolimes in heritage conservation are summarized, including consolidation of stone, ceramics, lime mortars and mural painting, as well as deacidification of paper, canvas, and wood. The advantages and limitations of this novel nanotechnology for cultural heritage conservation are outlined. Finally, some conclusions and areas for future research are presented.