Abstract
Portable unilateral NMR was used to quantitatively map in a fully noninvasive way the moisture distribution in an ancient deteriorated wall painting before and after an intervention to reduce the capillary raise of water through the wall. Maps obtained at a depth of 0.5 cm clearly showed the path of the capillary raise and indicated that, after the intervention, the moisture level was reduced. Maps obtained by measuring the first layers of the wall painting were affected by the critical environmental conditions of the second hypogeous level of St. Clement Basilica, Rome, and by the presence of salts efflorescence and encrustations on the surface of the wall painting. The morphology and the elemental composition of salts investigated by SEM-EDS indicated that efflorescences and encrustations were mostly constituted of gypsum and calcite. The presence of these salts is explained with the presence of high concentration of carbon dioxide and sulphur-rich particles due to pollution which, along with the high-moisture level and the extremely feeble air circulation, cause recarbonation and sulphation processes on the plaster surface.
Highlights
Water is one of the major causes of decay to masonry materials, and to building masonry belonging to cultural heritage sites [1,2,3]
Portable unilateral nuclear magnetic resonance (NMR) was used to quantitatively map in a fully noninvasive way the moisture distribution in an ancient deteriorated wall painting before and after an intervention to reduce the capillary raise of water through the wall
In a recent paper [6] we reported a multitechnique study consisting of microclimate monitoring, infrared thermography (IRT), gravimetric tests, and portable unilateral nuclear magnetic resonance (NMR) which allowed us to map the moisture distribution in a very deteriorated ancient wall painting
Summary
Water is one of the major causes of decay to masonry materials, and to building masonry belonging to cultural heritage sites [1,2,3]. In a recent paper [6] we reported a multitechnique study consisting of microclimate monitoring, infrared thermography (IRT), gravimetric tests, and portable unilateral nuclear magnetic resonance (NMR) which allowed us to map the moisture distribution in a very deteriorated ancient wall painting. In the framework of this study, IRT and gravimetric methods allowed the validation of portable unilateral NMR technique as a new analytical and noninvasive tool for mapping in situ the quantitative distribution of moisture in wall paintings, as well as in any porous material. Unilateral NMR can be successfully applied for mapping and evaluating the moisture distribution where other traditional techniques cannot be applied This is true in hypogeous environments, where the critical microclimate impairs the use of IRT [10, 11]. Because the surface of the wall painting is affected by efflorescences and encrustations, scanning electron microscopy (SEM) and energy dispersive X-Ray spectroscopy (EDS) were applied for characterizing the morphology and the elemental composition of the salts
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