Eleonora Del Federico

Noninvasive depth profiling of walls by portable nuclear magnetic resonance

AbstractA compact and mobile single-sided 1H NMR sensor, the NMR-MOUSE®, has been employed in the nondestructive characterization of the layer structure of historic walls and wall paintings. Following laboratory tests on a model hidden fresco, paint and mortar layers were studied at Villa Palagione and the Seminario Vescovile di Sant’ Andrea in Volterra, Italy. Different paint and mortar layers were identified, and further characterized by portable X-ray fluorescence spectroscopy where accessible. In the detached and restored fresco “La Madonna della Carcere” from the Fortezza Medicea in Volterra, paint and mortar layers were discriminated and differences in the moisture content of the adhesive that fixes the detached wall painting to its support were found in both restored and original sections. These investigations encourage the use of the portable and single-sided NMR technology for nondestructive studies of the layer structure and conservation state of historic walls. FigureA mobile NMR machine measuring a depth profile into a painted, old wall to unravel the layers from mortar and paint

Non-invasive characterization of polymeric materials in relation to art conservation using unilateral NMR combined with multivariate data analysis

This article shows how to interpret data obtained by unilateral NMR for the characterization of works of art using multivariate analysis. Transverse 1H relaxation decays acquired by a Carr–Purcell–Meiboom–Gill pulse sequence are directly treated by Principal Component Analysis (PCA) and projection to latent structure by partial least square (PLS). The advantage of this procedure is the avoidance of any ambiguity in the model. The NMR signal is formed by a number of different hydrogen spins rendering the resulting relaxation decays multi-exponential. Therefore conventional approaches of fitting call for the use of mono-, bi-, or multi-exponential models yielding results depending on the choice of the model function. We demonstrate the technique on three examples: characterization of a set of resins representative for modern materials in art and design artefacts, mapping the state of degradation of an art work made of latex, and the analysis of a depth profile of an aged urethane rubber sample. In situ measurements often result in low signal-to-noise ratio data and the suggested technique does not only allow an unambiguous model-free approach, but is also robust against such low sensitivity data.

MRI and Unilateral NMR Study of Reindeer Skin Tanning Processes

The study of arctic or subarctic indigenous skin clothing material, known for its design and ability to keep the body warm, provides information about the tanning materials and techniques. The study also provides clues about the culture that created it, since tanning processes are often specific to certain indigenous groups. Untreated skin samples and samples treated with willow (Salix sp) bark extract and cod liver oil are compared in this study using both MRI and unilateral NMR techniques. The two types of samples show different proton spatial distributions and different relaxation times, which may also provide information about the tanning technique and aging behavior.

1H NMR study and multivariate data analysis of reindeer skin tanning methods

Reindeer skin clothing has been an essential component in the lives of indigenous people of the arctic and sub‐arctic regions, keeping them warm during harsh winters. However, the skin processing technology, which often conveys the history and tradition of the indigenous group, has not been well documented. In this study, NMR spectra and relaxation behaviors of reindeer skin samples treated with a variety of vegetable tannin extracts, oils and fatty substances are studied and compared. With the assistance of principal component analysis (PCA), one can recognize patterns and identify groupings of differently treated samples. These methods could be important aids in efforts to conserve museum leather artifacts with unknown treatment methods and in the analysis of reindeer skin tanning processes. Copyright