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Oil paint is a dynamic system that undergoes chemical alteration on several time and length scales. At the short term, curing reactions are necessary for oil to dry properly. At longer time scales, a wide variety of other chemical processes can negatively affect the visual appearance or mechanical properties of historical artistic paint systems. The development of chemical imaging methods capable of covering length scales continuously from the millimetric to micro- or even nanoscale is key in understanding the chemical composition of a painting and the historical changes thereof. Such imaging methods can help in assessing to which extent the original painting’s composition may have been modified by chemical degradation processes. Processes that occur in the highly heterogeneous mixtures of binders, pigments, additives, alteration products and possibly later repainting and restoration treatments. Establishing the precise biography of the painting contributes to evaluate its authenticity. New modalities and novel methods of microchemical imaging provide access to previously unexplored length scales, are capable of better differentiation between the various oil paint components (original composition or later addition), and allow performing faster analysis to produce higher definition images. In this review, we report on recent methodological developments and future prospects to determine oil paints composition using microchemical imaging at the micro- and nanoscale.

International audience; This work proposes a multi-analytical approach to determine the additives in historical mortars, the use of which is widely described in bibliographical sources, but has rarely been reported in the literature. A protocol to thoroughly analyse mortars was created (optical microscopy, X-ray diffraction, infrared spectroscopy, thermal analyses and gas chromatography – mass spectrometry). These techniques had already been carried out on samples from various sites from the Roman to the modern era, finding that additives had only been used in the mortars from the internal masonry at our sampling site: the medieval military shipyard of Amalfi (Italy). The investigations yielded information on the production technology, and FT–IR and GC–MS revealed a saccharide material-based additive in the mortars, of plant origin. The FT–IR spectra suggested the presence of a natural gum, which has been used since ancient times to strengthen the cohesion properties of mortars and their resistance to tensile stress.

Fluorescence LIDAR imaging has been already proposed in several studies as a valuable technique for the remote diagnostics and documentation of the monumental surfaces, with main applications referring to the detection and classification of biodeteriogens, the characterization of lithotypes, the detection and characterization protective coatings and also of some types of pigments. However, the conservation and documentation of the cultural heritage is an application field where a highly multi-disciplinary, integrated approach is typically required. In this respect, the fluorescence LIDAR technique can be particularly useful to provide an overall assessment of the whole investigated surface, which can be profitably used to identify those specific areas in which further analytical measurements or sampling for laboratory analysis are needed. This paper presents some representative examples of the research carried out in the frame of the PRIMARTE project, with particular reference to the LIDAR data and their significance in conjunction with the other applied techniques. One of the major objectives of the project, actually, was the development of an integrated methodology for the combined use of data by using diverse techniques: from fluorescence LIDAR remote sensing to UV fluorescence and IR imaging, from IR thermography, georadar, 3D electric tomography to microwave reflectometry, from analytical techniques (FORS, FTIR, GC-MS) to high resolution photo-documentation and historical archive studies. This method was applied to a 'pilot site', a chapel dating back to the fourteenth century, situated at 'Le Campora' site in the vicinity of Florence. All data have been integrated in a multi-medial tool for archiving, management, exploitation and dissemination purposes.