1,721,041 research outputs found
New Frontiers in Application of FTIR Microscopy for Characterization of Cultural Heritage Materials
No full textWe present an overview of recent advances in the application of Fourier Transform Infrared (FTIR) microscopy for analysis of complex, multicomponent, and multilayer samples such as those typically encountered in the field of heritage materials. This technique is particularly useful since it allows identification and localization of both organic and inorganic (if IR active) compounds. New improvements have been possible thanks to the introduction of ad hoc sample preparation methods to obtain either thin or cross sections that allow both avoidance of contamination from organic embedding resin and improvement of the quality of the acquired spectra. Moreover, integrated use of spectra registered in the near-infrared (NIR) and mid-infrared (MIR) regions allows better comprehension of cross section composition. Data interpretation has been improved thanks to the development of chemometric methods for elaboration of hyperspectral data. A new and very promising field is the development of enhanced FTIR methods for detection of trace components in microextracts. These systems, allowing detection of extractable organic compounds from about 0.1 mg of sample, will be extremely useful in the future for analysis of natural and synthetic colorants, varnishes extracted, for instance, from cotton swabs used during cleaning of paintings, and organic residues on archeological remains
SCIENTIFIC EXAMINATION FOR THE INVESTIGATION AND CONSERVATION OF FAR EAST ASIAN MURAL PAINTINGS
No full textIf compared to western wall paintings, the study, conservation and restoration of far east Asian wall paintings is a more difficult task, owing not only to the varied supports and painting material constituents they are made of, but also to the particular social environments in which they are located and the consequences it has on the adopted theoretical and practical approaches to conservation. For instance, in some countries an element of devotion and the desire to offer the best to the gods leads religious communities to rebuild damaged sections of structures instead of trying the preserve them.
Therefore, when talking about far east Asian mural paintings conservation the main issue is their imminent risk of loss or damage. This has sometime led to certain standardization of treatments (pigments, consolidants, protective coatings and industrial products) as it happened, for example, with external architectural polychromies where the need to identify alternative treatments for conserving exterior surfaces that have retained a reasonable amount of historical material is of the outmost importance. Consequently further scientific research on traditional materials, techniques and skills would be desirable and could continue to improve the results in the future. In this regard collaborative studies on the subject of far east Asian architectural polychromy at the international level should be encouraged and implemented
Characterization of outdoor bronze monument patinas: the potentialities of near-infrared spectroscopic analysis
No full textThe corrosion products usually found on outdoor bronzes are generated by the interaction between the metal alloy and the atmospheric pollutants. To protect the external surface of bronzes, different organic materials (natural or synthetic) can be applied, creating over time a patina consisting of a complex mixture of inorganic and organic degraded components. The correct chemical characterization of patina constituents is fundamental to define the state of conservation of a metal artwork and address proper restoration actions. In this paper, we evaluated the potentialities of near-infrared (NIR) reflectance microscopy (4000–7500 cm−1) as complementary method to mid-infrared (MIR) analyses for the characterization of bronze patinas. Although NIR spectroscopy has been already used in the field of heritage science, its application for the characterization of bronze patinas is almost unexplored. In this paper, several corrosion products usually found on the surface of outdoor bronze sculptures were synthesized, characterized, and submitted to the NIR-MIR total reflection analysis to build up a reference spectral database. We devoted particular attention to the NIR features of copper hydroxychlorides, such as atacamite and paratacamite, which have not been studied in detail up to now. A selection of organic-based formulations, commonly used by restorers to protect the bronze surface against the outdoor aggressive environment, were also considered as references. Successively, NIR-MIR reflectance microscopy was successfully employed for the analysis of patina micro-samples collected from the bronze statues of the Neptune Fountain (sixteenth century) located in Bologna. The obtained results demonstrate the ability of NIR spectroscopy to identify organic and inorganic patina constituents, even in mixtures. In addition, the study can be considered as a proof of concept for the possible future application of the technique for in situ diagnostic campaigns on bronze sculptures
Immunochemical Micro Imaging Analyses for the Detection of Proteins in Artworks
No full textThe present review is aimed at reporting on the most advanced and recent applications of immunochemical imaging techniques for the localization of proteins within complex and multilayered paint stratigraphies. Indeed, a paint sample is usually constituted by the superimposition of different layers whose characterization is fundamental in the evaluation of the state of conservation and for addressing proper restoration interventions. Immunochemical methods, which are based on the high selectivity of antigen–antibody reactions, were proposed some years ago in the field of cultural heritage. In addition to enzyme-linked immunosorbent assays for protein identification, immunochemical imaging methods have also been explored in the last decades, thanks to the possibility to localize the target analytes, thus increasing the amount of information obtained and thereby reducing the number of samples and/or analyses needed for a comprehensive characterization of the sample. In this review, chemiluminescent, spectroscopic and electrochemical imaging detection methods are discussed to illustrate potentialities and limits of advanced immunochemical imaging systems for the analysis of paint cross-sections
Evaluation of the effect of different paint cross section preparation methods on the performances of Fourier transformed infrared microscopy in total reflection mode
No full textThe stratigraphical characterization of polychrome samples may be considerably limited by sample preparation procedure both in terms of embedding material and surface polishing. Indeed, the use of synthetic embedding media may contaminate the sample, while the surface morphology obtained after polishing may affect the performances of different analytical techniques such as FTIR microscopy both in attenuated total reflection (ATR) and in total reflection mode.
In particular, in ATR an optimal contact between the crystal and the sample is necessary, while in total reflection sample roughness affects the shape and the intensities of the spectra.
Recently, different sample preparations were studied and compared taking into account the performance of FTIR microscopy in ATR mode but, as this approach presents some disadvantages, such as the risk of damaging the sample due to the pressure of the crystal, the present research work has been focused on total reflection, which works in non-contact mode. Two sample preparation methods based on the use of cyclododecane and KBr, recently proposed for their capability to reduce contamination effects, were selected to evaluate the performances of FTIR microscopy in total reflection mode on samples characterized by a different surface morphology. In particular the sample prepared with epoxy resin and CDD has been subjected to a simple cut, producing an inhomogeneous surface, with a high roughness, while the sample embedded with KBr has been prepared with a fine polishing procedure, obtaining an optically flat surface.
Both of the preparation procedures were applied to obtain two paint cross-sections from fragments collected in the same area from a mural temple (15th century) located in Thubeken Lhakhang, Nepal. The cross sections were analysed with FTIR microscopy in total reflection mode, in order to compare the effect of the preparation methods on the spectral response. Line-scan imaging measurements were carried out on both of the samples and the resulting chemical images were re-constructed by a chemometric approach based on principal component analysis.The stratigraphical characterization of polychrome samples may be considerably limited by sample preparation procedure both in terms of embedding material and surface polishing. Indeed, the use of synthetic embedding media may contaminate the sample, while the surface morphology obtained after polishing may affect the performances of different analytical techniques such as FTIR microscopy both in attenuated total reflection (ATR) and in total reflection mode.In particular, in ATR an optimal contact between the crystal and the sample is necessary, while in total reflection sample roughness affects the shape and the intensities of the spectra.Recently, different sample preparations were studied and compared taking into account the performance of FTIR microscopy in ATR mode but, as this approach presents some disadvantages, such as the risk of damaging the sample due to the pressure of the crystal, the present research work has been focused on total reflection, which works in non-contact mode. Two sample preparation methods based on the use of cyclododecane and KBr, recently proposed for their capability to reduce contamination effects, were selected to evaluate the performances of FTIR microscopy in total reflection mode on samples characterized by a different surface morphology. In particular the sample prepared with epoxy resin and CDD has been subjected to a simple cut, producing an inhomogeneous surface, with a high roughness, while the sample embedded with KBr has been prepared with a fine polishing procedure, obtaining an optically flat surface.Both of the preparation procedures were applied to obtain two paint cross-sections from fragments collected in the same area from a mural temple (15th century) located in Thubeken Lhakhang, Nepal. The cross sections were analysed with FTIR microscopy in total reflection mode, in order to compare the effect of the preparation methods on the spectral response. Line-scan imaging measurements were carried out on both of the samples and the resulting chemical images were re-constructed by a chemometric approach based on principal component analysis. (C) 2013 Elsevier B.V. All rights reserved
Comparison between destructive and non-destructive quantitative chemical analyses of glass mosaic tesserae
No full textA very useful non-manipulative and non-destructive analytical technique for in situ investigations in the cultural heritage field is the X-ray Fluorescence (XRF) portable spectrometer. This technique has been successfully employed in the analyses of various type of materials but up to now only few application have been found on the use of portable XRF for the analyses of glasses and obsidians due to the limit of the technique in the detection of the light elements (typically Na and Mg). In this work we have checked the applicability of this technique for the quantitative analyses of a set of mosaic tesserae by comparing the data obtained by the XRF portable spectrometer with those previously obtained by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) on a set of mosaic tesserae from S.Vitale in Ravenna. This is a laboratory test to be developed in an in situ analytical protocol at use and advantage of art historians and conservators for their “first-sight” knowledge of the mosaic glass characteristics
A portable device for on site detection of chicken ovalbumin in artworks by chemiluminescent immunochemical contact imaging
No full textThe development of user-friendly devices for on site analysis and characterization of painting materials is one of the most challenging objectives in the diagnostics for cultural heritage. Thanks to the specificity of antigen-antibody reactions, immunological methods have been already successfully applied for the detection of proteins and for their localization within painting stratigraphies. Moreover, by combining the advantages of the immunological techniques with the high detectability offered by chemiluminescence detection, it has been possible to achieve good analytical performance and very low detection limits. This work was aimed at developing a portable analytical device for the detection of chicken ovalbumin (a protein found in egg tempera and in egg-based protective varnishes) in painting samples employing ready-to-use analytical cartridges and a thermoelectrically-cooled CCD camera as a chemiluminescence detector. The protein was extracted from using a simple procedure and revealed by a non-competitive immunoassay with chemiluminescence contact imaging detection. The assay was simple, fast and suitable for the detection of ovalbumin in small samples. This analytical system provided positive identification of ovalbumin in samples obtained from both fresh or artificially aged paint reconstructions and historical paintings. It might be easily employed in different contexts (such as small museums, restoration laboratories or even on site) by restorers to obtain prompt information during restoration actions, such as cleaning operations. In perspective this device could be also employed for the detection of other proteinaceous and organic painting component
FT-NIR microscopy: an advanced spectroscopic approach for the characterisation of paint cross sections
No full textThe present research was aimed at exploiting and evaluating the potentialities of FT-NIR microscopy, as a complementary approach to analysis in the MIR region, for the chemical characterisation of paint cross sections. Even if FT-NIR technique is still underutilised in the field of cultural heritage investigations, the integrated use of information recorded in the NIR and in the MIR regions proved to be extremely useful in the molecular investigation of organic and inorganic substances. In fact, combination and overtone bands present in the NIR region, even if weaker and less selective than those in the MIR region, are not distorted by reflection phenomena. Furthermore, NIR spectra can be efficiently used as a spectral fingerprint for the stratigraphic characterisation of paint cross sections. The proposed analytical protocol was applied on two historical samples, presenting different stratigraphic structures. Suitable chemometric methods were applied for the elaboration of multivariate chemical maps recorded in the range 700–7500 cm− 1. In particular, a comprehensive and efficient procedure based on an interactive brushing approach, which combines the structural information of the score scatter plots with the spatial information of the PC score maps, was used. Interestingly, NIR data allowed a thorough characterisation of paint structures, providing information for the identification of components and suggesting the differentiation among different types of proteins. Moreover, NIR spectra permitted to achieve an efficient distinction of different classes of natural resins, demonstrating that, even working at a microscopic level, the NIR region may support the identification of different terpenoid materials. Multivariate analysis performed on MIR data did not provide satisfactory results, probably due to the distortion of the spectra and overlapping of bands. Nevertheless, MIR outcomes were investigated to support the interpretation of NIR spectra and in attempt to define an integrated protocol for the characterisation of complex paint mixtures
A follow-up on the analytical study of discolouration of the marble statues of Orsanmichele in Florence
No full textThe research complements the complex study carried out to understand the source of brown discolourations of ten marble statues in the Church of Orsanmichele in Florence, Italy. Originally located in exterior niches, the statues were restored to reverse the extensive alterations they had undergone throughout the centuries. One of the major alterations was the application of a dark brown patina that dated just after 1789. After the statues were placed indoors, brownish discolourations started to appear on their surfaces. Cross sections were examined using FTIR mapping and immunological methods. In parallel, the pyrolysis-gas chromatography/mass spectrometry (py-GC/MS) data already obtained from the statues’ scrapings were compared with data from aged casein films applied to microscope glass slides and aged milk-treated marble. All the statues had been treated with milk-based substances before the time the bronze patina was applied. The values of temperature and illumination of the room were important factors in the ageing of organic substances and in the formation of calcium oxalates. It is likely that products of thermo-oxidation and photo-oxidation of the oils together with the oxalates caused the darkening. The marble samples corresponded to a Lunense provenance
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