T emitted from particular supplies within the form of fluorescence when these materials are exposed to UV radiation. This method allows to acquire facts in regards to the presence of fluorescent materials, i.e., colorants, varnishes, binders primarily based on egg or oils, restoration solutions and any material which shows fluorescence just after UV light excitation [18,19]. Moreover, it’s feasible to use also transportable multispectral imaging systems, which can recognize the presence of fluorescent components in wall paintings in relation to their multispectral properties [20]. Time-resolved laser-induced fluorescence spectroscopy (TR-LIF) and fluorescence lifetime imaging (FLIM). These two strategies allow to detect the presence of organic fluorescent materials and their distribution within the wall paintings [21]. Mid-Fourier transform infrared spectroscopy (FTIR) fiber reflectance spectroscopy. The FTIR spectroscopy by portable instruments is generally employed to acquire information concerning the presence of each organic and inorganic material [224]. Hyperspectral imaging inside the NIR and mid-IR region. Present scientific interest is focused around the progress of mapping/imaging multi-/hyperspectral techniques, considering that area examination naturally meets the demands of a holistic art strategy by revealing not only the chemical composition of painting supplies but also their semi quantitative spatial distribution with respect to what is visible to the naked eye. These approaches have been assessed and supplied promising results in other varieties of paintings (having a clearly greater binder to 2-Hydroxychalcone Epigenetic Reader Domain pigment ratio) but possibly additional developments will allow their productive application for the screening and mapping of also in wall paintings [257]. Raman spectroscopy. It has been utilised for a lot of years inside the study of cultural heritage, particularly for the examination of materials of inorganic nature, but viewed as potentially usable for the study of organic media, as exposed by some papers carried out on pure components and pigment/binder mixtures [28]. Some authors think about Raman microscopy the perfect strategy for the investigation of components applied on functions of art VU0359595 supplier simply because it’s extremely sensitive, dependable, specific, nondestructive, with high spatial resolution (normally ranging amongst 1 and 10 ) and can be employed in situ, consequently avoiding any sampling and consequently any damage to the item below investigation [29].Appl. Sci. 2021, 11,6 ofIntegrated multispectral imaging systems. This sort of imaging technique is based on the choice of certain wavelengths and also the acquisition of black and white pictures, so as to underline the presence of non-homogeneous regions within the surface This method provides non-invasive mapping and classification of materials with diverse chemical and optical properties. It can be mentioned right here, for the reason that it truly is very fascinating, but you can find no recognized applications that have allowed to characterize organic binders [30]. Fiber optic reflectance spectroscopy (FORS). The FORS approach provides information and facts about supplies by analyzing their optical properties [31].Pretty normally to finish the study it is necessary to acquire precise information and facts about chemical composition, the presence of degradation products or data about the stratigraphic distribution of organic binding media inside the wall paintings. For this reason, soon after a basic investigation performed by non-invasive methods, the taking of samples is essential, in order to carry out a detailed characterization of analytes. F.