Search

In this study a multi-analytical approach has been performed to characterise the constitutive materials of an ancient painted barkcloth or Tapa. Originating from Wallis Island, Polynesia, this cloth likely served utilitarian or ceremonial purposes and is part of the Felice Junck collection at the Pigorini, Muciv museum of Rome. During a recent conservation project, some micro-samples were taken from the support, brown and black painted areas and were investigated using the complementarity of SEM-EDX, FT-IR, Raman/SERS and solid-state 13C NMR and 1H HR-MAS spectroscopy. The combination of these techniques allowed the chemical characterization of the constitutive materials, from distinguishing the lignin and cellulose content of the support to the use of organic materials including condensed tannins (catechin, anthocyanidins, alkaloids), phlobaphene and vegetal anthraquinone based Morinda genus dyes for the decorations. A primary focus was placed on an understanding of its state of conservation where data of alteration products collected, namely metal carboxylates and oxalates can serve to formulate apt restoration efforts for this specific artefact.

The quantitative evaluation of the three-dimensional (3D) morphology of porous composite materials is important for understanding mass transport phenomena, which further impact their functionalities and durability. Reactive porous paint materials are composites in nature and widely used in arts and technological applications. In artistic oil paintings, ambient moisture and water and organic solvents used in conservation treatments are known to trigger multiple physical and chemical degradation processes; however, there is no complete physical model that can quantitatively describe their transport in the paint films. In the present study, model oil paints with lead white (2PbCO3·Pb(OH)2) and zinc white (ZnO) pigments, which are frequently found in artistic oil paintings and are associated with the widespread heavy metal soap deterioration, were studied using synchrotron X-ray nano-tomography and unilateral nuclear magnetic resonance. This study aims to establish a relationship among the paints’ compositions, the 3D morphological properties and degradation. This connection is crucial for establishing reliable models that can predict transport properties of solvents used in conservation treatments and of species involved in deterioration reactions, such as soap formation.

Agar is an interesting and versatile biopolymer capable of forming hydrogels useful in different applications. In particular, in the field of Cultural Heritage agar gels are often used as tools for cleaning the surfaces of artifacts. Agar gels are thermoreversible, peelable materials, exhibiting high retention of water and an intrinsic cleaning capability that can be increased and modulated by loading different cleaning agents. Agar gels are able to solubilize and retain dirt, and allow a confined release of the liquid phase, which is especially important when they are applied on water sensitive substrates. A detailed knowledge of the role of water in agar gels and of water/agar interactions is important to fully understand the properties and performances of agar gels as cleaning materials. Here we report the results of a systematic study aimed at exploring the water state and the types of water (i.e. bound non-freezable, bound freezable and freezable bulk-like) in agar hydrogels prepared from four different types of commercial agar powders. The influence of agar concentration on the water behaviour in the hydrogels was also investigated. The total water content, the identification and quantification of the different types of water was carried out by gravimetric, thermogravimetric and calorimetric analyses, while water mobility and localization in the gel network were investigated by unilateral H-1 NMR. Moreover, H-1 NMR depth profiles of agar gels applied on Noto stone specimens were collected to monitor the gel deformation due to water release and to evaluate the ability of the gel in controlling the water release into a porous material. (C) 2018 Elsevier B.V. All rights reserved.

Heavy metal carboxylate degradation severely affects thousands of oil paintings. Relative humidity has been reported to accelerate the rate of the reactions. To evaluate its role further, water diffusion and molecular mobility of protons in linseed oil-based lead white paints were studied by unilateral NMR and 1H HRMAS spectroscopy. The results indicate that exposure to high %RH for relatively long times affects the dynamics of the oil paint's mobile fraction and that the effect is more pronounced as the thickness of the film increases. It was found that the paint can absorb appreciable amounts of water and has a porosity of approximately 6 % available for the diffusion of water, for which a regime of restricted diffusion was observed. Furthermore, the presence of bound and free-moving water, due to the possible formation of hydrated ionic-group clusters, supports the hypothesis of a polymeric/ionomeric network, as well as regions of essentially water free to move as in the bulk. The findings allow a better understanding of the role of water as a factor activating the degradation process in linseed oil-based lead white paints.

Highly performing cleaning systems based on hydrogels for buildings and artefacts were studied by unilateral NMR. Specifically, the release and diffusion of water from gellan gum formulations at the gel stone interface were investigated. The study was carried out by applying gel formulations to stone specimens with different porosimetric properties, namely Yellow Tuff of Via Tiberina and Lecce stone. NMR measurements and a suitable processing of data allowed the obtainment of the total open porosity, the average pore size, and the tortuosity of the stones. Properly calibrated H-1 NMR depth profiles with micrometric resolution were used to evaluate the effective volume of absorbed water, the distribution of water in porous stone specimens, and the degree of saturation. The deformation coefficient of the gel after water release was also determined. The obtained results indicated that the performance of the gel depends not only on its physical-chemical properties but also on the porosimetric properties of the stone to which the gel is applied. Therefore, the knowledge of the porosimetric properties of the material is important for selecting a suitable and highly performing gel cleaning system. (C) 2017 Elsevier Inc. All rights reserved.

A multi-analytical study was carried out on materials, techniques, and state of conservation of a set of detached Nubian mural paintings, originally belonging to the 10th century pictorial cycle of the church of Sonqi Tino, Sudan (70 km south of the Egypt–Sudan border). These paintings represent one of the very few examples of Christian Nubian pictorial cycles preserved from the wide defacement experienced by these artifacts with the building up of the Aswan Dam. Non-invasive NMR depth profiling was used to preliminary study the hydrogen rich layers of the detached mural paintings. By this technique, it was possible to perform a virtual coring with a reconstruction of the complex series of layers that characterize the investigated artifacts. Then, micro-sampling and cross-section examination by SEM-EDX, micro-Raman, micro-FTIR, and 27Al and 29Si MAS NMR, allowed us to shed light on materials and technology exploited by the Medieval Nubian painters, with the identification of pigments and composition of the original primer, obtaining also information on layering of materials used by conservators during the detachment of the paintings and their transfer to a new support. The combination of preliminary non-invasive investigation with a set of micro-invasive analytical techniques allowed us to set up a protocol for a satisfactory decoding of the multilayered complex systems that characterize the detached paintings.

The effectiveness and the mechanism of copper stain removal from stones by agar gels was systematically studied using marble laboratory specimens, stained and cleaned in well-controlled and reproducible conditions. The same cleaning procedure was also applied on the marble base of Napoleon's statue by A. Canova. The water release from agar gels to stones was investigated by capillarity absorption and unilateral Nuclear Magnetic Resonance. The cleaning by different agar gel formulations (pure and added with chemicals) was studied both on the stone substrate (optical microscopy and colour measurements) and in the gels (inductively coupled plasma-atomic emission spectrometry, electron paramagnetic resonance spectroscopy). Among the considered cleaning systems, the most effective ones for copper removal were agar gels 3% containing additives, with no significant difference among the used additives. However, agar gels with additives host copper in different ways: in gels added with ethylenediamine tetraacetic acid (EDTA), all copper centers are coordinated, while copper centers are also dispersed in water within gels added with ammonium citrate tribasic (TAC). The stain cleaning process of stones probably starts with the diffusion of water at the gel-stone interface, but it finds the driving force in the copper coordination. (C) 2016 Elsevier B.V. All rights reserved.

The use of nanotechnology in conservation is a relatively new concept. Usually, classical cleanup methods take into account the use of other chemicals: On the one hand they help the environment destroying pollutants, but on the other hand they often become new pollutants. Among the new oxidation methods called advanced oxidation processes, heterogeneous photocatalysis has appeared an emerging technology with several economic and environmental advantages. A new sol-gel method of synthesis of TiO2 anatase is reported in this work using lithium and cobalt (II) salts. The activation energy of the doped photocatalyst was analyzed by solid-state UV-Vis spectrophotometer. The mobility of Li ions on TiO2 NPs surface was studied by Li-7 MAS NMR spectroscopy. Use of doped nanotitania is suggested from authors for the removal of pollutants in confined areas containing goods that must be preserved from decomposition and aging phenomena.

In this paper five case studies illustrating applications of NMR (Nuclear Magnetic Resonance) in the field of cultural heritage, are reported. Different issues were afforded, namely the investigation of advanced cleaning systems, the quantitative mapping of moisture in historic walls, the investigation and evaluation of restoration treatments on porous stones, the stratigraphy of wall paintings, and the detection of CO2 in lapis lazuli. Four of these case studies deal with the use of portable NMR sensors which allow non-destructive and non-invasive investigation in situ. The diversity among cases reported demonstrates that NMR can be extensively applied in the field of cultural heritage.

open 10 no In this study, portable NMR was applied to monitor and evaluate cleaning treatments on the surface of a 16th century Italian wall painting. Due to the complexity of the state of degradation of the wall painting, a campaign of measurements was carried in situ to evaluate the performance of traditional and innovative eco-friendly cleaning systems such as sulphate-reducing bacteria D. vulgaris confined in hydrogels, and to compare two different cleaning systems used to remove a degraded hydrophobic organic layer. Specifically, NMR stratigraphy allowed to determine the thickness of the organic layer covering the surface of the wall painting, its distribution in the wall painting, the presence of residues after applying the cleaning treatment, and to evaluate and compare the effectiveness of applied treatments. A new analytical parameter here named the solubilization degree of the cleaning system permitted the selection of the most performing treatment. 1H NMR depth profiles allowed to evaluate changes in the permeability of the wall painting caused by the presence of organic substances during the application of water-based cleaning systems, and to evaluate the water content and its depth of penetration in the wall painting. Changes in permeability were estimated calculating another new analytical parameter, i.e. the percentage of water saturation before and after the application of the cleaning treatment. Depth profiles also permitted the evaluation of the degree of wettability of the wall painting surface as a function of the time of application, and the obtainment of a detailed information about the interaction between water molecules, the gel network and the surface of the wall painting. Finally, to obtain the chemical characterization of the artefact surface a multi analytical approach was applied using both portable and micro-invasive analytical methodologies. embargoed_20200501 Di Tullio, Valeria; Sciutto, Giorgia; Proietti, Noemi; Prati, Silvia; Mazzeo, Rocco; Colombo, Chiara; Cantisani, Emma; Romè, Valentina; Rigaglia, Davide; Capitani, Donatella Di Tullio, Valeria; Sciutto, Giorgia; Proietti, Noemi; Prati, Silvia; Mazzeo, Rocco; Colombo, Chiara; Cantisani, Emma; Romè, Valentina; Rigaglia, Davide; Capitani, Donatella