IR spectroscopy is a powerful tool for characterising the chemistry and chemical variability of organic remains in fossils. Optical-Photothermal InfraRed (O-PTIR) and Atomic Force Microscopy-InfraRed (AFM-IR) are novel IR spectroscopy techniques based on the photothermal effect that are able to bypass the diffraction limit imposed to classical IR techniques to reach micrometric and nanometric lateral resolutions respectively. Here we introduce a novel methodology to characterise, across multiple spatial scales, the heterogeneity of a fossil-amber interface. By employing an ultramicrotomy-based sample preparation, we demonstrate the potential of such an approach to collect both IR spectra and maps, revealing key information on the chemical heterogeneity within the amber. This includes insights into the potential hydrolysis of the amber filling the inclusion, as well as the infrared signature of the fossilised cuticle, demonstrating the inherent complementarity of each technique. Based on the case study of the long-term interactions of insect cuticle fossilisation and amber, we evaluate the strengths and limitations of each technique, both technically and experimentally, to assist future users in assessing their suitability for the study of ancient materials.

Following the industrial revolution and the modernization of chemistry, purple became one of the most popular colors in the palettes of late 19th- to 20th-century painters. Among them, Robert Delaunay (1885-1941) was one of the key artists of the avant-garde movement in France in the early 20th century. Although widely used in modern and contemporary paintings, inorganic purple pigments of the cobalt phosphate and cobalt arsenate families have been little studied chemically until now. The diversity of emerging chemical syntheses resulted in a wide range of products, characterized by a high diversity of hues, function of their respective composition, and crystal structures. The present work combines structural and optical analyses to probe the purple pigments used by Delaunay. Reference materials synthesized in the laboratory were characterized via synchrotron radiation-based high-angular-resolution X-ray powder diffraction and UV-vis-NIR spectroscopy. Structure-color relationships were established for the first time for several inorganic compounds of the Co-P/As family. Two of Robert Delaunay's earliest masterpieces conserved at the Centre Pompidou in Paris were probed in situ via X-ray powder diffraction in imaging mode and fiber optic UV-vis-NIR reflectance spectroscopy. The results highlight the decisive effect of their structural chemistry on the palettes of modern and contemporary painters.

Understanding paint structures at the nanoscopic level can address key questions related to artistic techniques, paint formulation, and long-term preservation of artworks. This involves examining spatial chemical complexity, the formation of molecular networks, and interactions between organic and inorganic constituents. Depending on the paint preparation methods, proteins and drying oils, the most common binders in traditional artistic practices, can be integrated to produce paints with diverse structures and nanoscale chemical intricacies. In this study, we utilize atomic force microscopy-based infrared spectroscopy (AFM-IR) to investigate the spatial chemical complexity and reaction pathways of organic species in artists' paints, including oil, tempera, and mixed-media tempera grassa. By analyzing these paints at the nanoscale, we established connections between their structural organization, chemistry, and formulation.

Flax plays an important role in art, especially for painters. Flax seeds are ground into linseed oil, which is used as binder for oil paints, and fibers are used to make linen canvas as a support for paintings. Because of the rapid growth of flax, linen canvas fiber and linseed oil are considered good candidates for the radiocarbon ( 14 C) dating of paintings. However, the time necessary to transform flax into a linen canvas must be estimated in order to determine the completion date of paintings. Based on the paintings of the French painter Pierre Soulages (1919–2022), who titled his works with the day on which he considered them finished, the time elapsed between completion of the painting and harvesting of the flax was determined for 25 canvases and 13 oil binders. For the canvases, three periods can be distinguished between 1956 and 1981 with durations of 5±1 years in the 1950s, 3±2 years in the 1960s and 11±3 years for the paintings from the 1970s–1980s. For the oil, the time elapsed between the date indicated by the artist and the 14 C calibrated date has a mean value of 3±2 years in the 1950s and 1960s and more than 15 years in the 1970s. These long time lags could be due to the massive change in flax processing, which was relocated, resulting in longer times between flax harvesting and canvas marketing. The determination of these time lags enables us to better interpret the 14 C dating results for the paintings.

This paper investigates the alteration of copper acetate (verdigris) and resinate green pigments widely used in oil paintings during the Middle Ages and Renaissance periods. These are bimetallic Cu(II) complexes. Their alteration consists in a color change of these bimetallic pigments from green into brown resulting in a darkening.By combining micro-analysis of both historical painting samples and analogue mock-ups this study elucidates the interactions between pigments and organic oily matrix and the chemical changes leading to the long-term degradation of copper acetate and resinate.Different analytical techniques were combined to characterize browning and identify degradation markers. The use of multimodal micro- spectroscopic techniques with a high lateral resolution (such as scanning electron microscopy, infrared micro spectroscopy, synchrotron photoluminescence, synchrotron micro-X-ray absorption near edge spectroscopy at the Cu K-edge) proved to be successful for the characterization of paint stratigraphy. The study shows the development of the pigment degradation from the surface to the inner painted layers, its facilitated propagation through defects (as cracks) and the influence of light and oxygen.The reproduced alteration in model samples fits with the ageing of masterpiece paintings. Finally, the browning mechanism is attributed to the formation of new copper complexes resulting from the ageing of organic binder and its interaction with copper bimetallic, without any detected structural modification of pigments in altered and non-altered areas.

The application of X-ray methods (using conventional sources or synchrotron radiation) for investigating degradation phenomena in paintings has significantly increased in the last two decades. This rise is due to their ability to provide spatially resolved elemental, molecular, and structural information from the macroscopic to the nanoscopic levels. This review will focus on the application of latest-generation X-ray techniques, including X-ray fluorescence (XRF), X-ray absorption spectroscopy (XAS), and X-ray diffraction (XRD), to study the alteration processes of pigments in paintings. The first part outlines the fundamentals of XRF, XAS, and XRD techniques and then describes the corresponding instrumental set-ups used for non-invasive macro-scale mapping of paintings and synchrotron radiation-based X-ray analysis of paint micro-samples. Subsequent sections will cover advancements in X-ray data analysis software, workflow management systems, Open Science and FAIR data initiatives, alongside practical aspects of sample preparation and issues concerning X-ray-induced damage to paints. The final section will review degradation phenomena resulting from chemical changes of selected classes of pigments. This will involve describing key findings obtained from paintings, related micro-samples, and artificially aged paint mock-ups. The outcomes discussed in this review highlight their crucial role in developing effective monitoring and preventive conservation strategies for artworks highly susceptible to degradation within heritage sites and museums.

The chemical investigation of modern art materials and synthetic paint materials has been a major focus of research in cultural heritage science over the past decade. Since the 1970s, street art has become an influential cultural movement with significant artistic and social impact in modern cities, and the conservation of relevant artworks related to urban neo-muralism has been increasingly recognized. Understanding these materials is critical to developing conservation strategies, as their composition continues to change with industrial innovation and regulatory changes. This study presents the application of an analytical approach that integrates chemical mapping based on spectroscopic approaches together with analytical pyrolysis, chromatography, and mass spectrometry to investigate two key case studies and provide insights into the evolution of street art materials over the past 30 years. This comprehensive approach provides a deeper understanding of the composition and transformation of urban art materials over time, overcoming the limitations of individual methods and revealing both organic and inorganic materials. This combined approach represents the state of the art in the study of synthetic paints used in modern art and provides new insights into the evolution of the formulation of materials used by street artists.

1. Polyacrylamide gel electrophoresis is commonly used to visualize mixtures of proteins, such as those embedded in calcareous biominerals. However, it is ineffective for the detection of biochromes, a major class of low molecular weight organic compounds commonly associated with calcified exoskeletons. 2. We describe a novel approach based on the coupling of electrophoresis and photoluminescence (PL) spectral imaging to reveal invisible biochromes, identify them chemically, provide evidence for their putative interaction with exoskeletal macromolecules and purify them in large amounts. Our protocol relies on three key-steps: a mild extraction of all organics from bleached skeletal powder (step 1); an optimized electrophoretic fractionation immediately followed by direct on-gel spectral image acquisition performed before classical gel staining (step 2); a large-scale purification via preparative electrophoresis coupled to PL spectral imaging, to obtain significant amounts of biochromes of interest (step 3). 3. Steps 1-3 were successfully applied to recent gastropod shell extracts, while steps 1 and 2 were applied to their fossil equivalents from the Eocene epoch (approximate to approximately 45 million years). In both cases, we were able to identify porphyrins associated with the shells via a spectrophotometric measurement of the luminescent bands directly on the analytical gel, even at low concentration in the case of fossil extract. For recent shell extracts, our approach allowed us to identify spectrophotometrically the tubes containing the invisible pigments, after preparative fractionation and fraction collection. 4. Our protocol enables direct on-gel identification of porphyrin molecules, even in trace amounts. It opens up new avenues for studying a wide range of biological composites, whether mineralized or not, that contain photoluminescent biochromes. It is particularly well-suited to ancient specimens and fossils to trace the origin and evolution of biochrome complexes in the geological record.

In palaeontology, the observation of morphological characters is at the heart of species determination. Nonetheless, since most fossils have undergone considerable morphological loss, distortion, and/or flattening throughout their taphonomic history, the use of visual techniques often remains limited. Complementary approaches such as geochemical analyses or molecular palaeontology are increasingly developed. However, them as well remain limited by the preservation state and diagenetic overprinting of the vast majority of fossils. Based on data obtained by state-of-the-art non-destructive synchrotron micro-X-ray fluorescence (µXRF) major-to-trace elemental mapping of Early Triassic Paris Biota fossils, we show here, at least within a single fossil fauna, the existence of a clade-specific elemental signature. Using complete multi-elemental µXRF spectra instead of elemental quantifications/concentrations, we set a data-formatting protocol that allows us to compare the morphology of the spectra. We then statistically demonstrate the existence of a geochemical discrimination between specimens of different clade despite intra-clade mineralogical variability, and build a "elemental-comparative taxonomic identification" model accordingly. The latter, that goes beyond the simple distinction of tissue nature or type of preservation, is all the more important as it appears to hold the potential to identify some hitherto unrecognizable specimens of the fossil record.

Identifying evidence of human modification of extinct animal remains, such as Pleistocene megafauna, is challenging due to the similarity of anthropogenic and non-anthropogenic taphonomic features observed under optical microscopy. Here, we re-investigate a Late Pleistocene ground sloth tooth from northeast Brazil, previously suggested as human-modified based only on optical observation. To characterize the macro- and micro-morphological characteristics of the marks preserved in this tooth and evaluate potential human modification, we used stereomicroscope and scanning electron microscopy (SEM) supplemented by energy dispersive spectroscopy (EDS), UV photoluminescence (UV/PL), synchrotron-based X-ray fluorescence (SR-XRF), and synchrotron micro-computed tomography (SR-µCT). These methods allowed us to discriminate non-anthropogenic taphonomic features (root and sedimentary damage), anthropogenic marks, and histological features. The latter shows the infiltration of exogenous elements into the dentine from the sediments. Our evidence demonstrates the sequence of anthropogenic and non-anthropogenic taphonomic modification of this tooth and supports its initial intentional modification by humans. We highlight the benefits of emerging imaging and spectral imaging techniques to investigate and diagnose human modification in fossil and archaeological records and propose that human modification of tooth tissues should be further considered when studying possibly anthropogenically altered fossil remains.

Over the last few decades, significant research efforts have been devoted to developing new cleaning systems aimed at preserving cultural heritage. One of the main objectives is to selectively remove aged or undesirable coatings from painted surfaces while preventing the cleaning solvent from permeating and engaging with the pictorial layers. In this work, we propose the use of electrospun polyamide 6,6 nonwovens in conjunction with a green solvent (dimethyl carbonate). By adjusting the electrospinning parameters, we produced three distinct nonwovens with varying average fiber diameters, ranging from 0.4 mu m to 2 mu m. These samples were characterized and tested for their efficacy in removing dammar varnish from painted surfaces. In particular, the cleaning process was monitored using macroscale PL (photoluminescence) imaging in real-time, while postapplication examination of the mats was performed through scanning electron microscopy. The solvent evaporation rate from the different nonwovens was evaluated using gravimetric analysis and Proton Transfer Reaction- Time -of -Flight. It was observed that the application of the nonwovens with small or intermediate pore sizes for the removal of the terpenic varnish resulted in the swollen resin being absorbed into the mats, showcasing a peel -off effect. Thus, this protocol eliminates the need for further potentially detrimental removal procedures involving cotton swabs. The experimental data suggests that the peel -off effect relates to the microporosity of the mats, which enhances the capillary rise of the swollen varnish. Furthermore, the application of these systems to historical paintings underwent preliminary validation using a real painting from the 20th century.

Enregistrer l’apparence des oeuvres d’art moderne est un enjeu majeur car celle-ci évolue dans le temps, et un défi qui exige le développement de nouveaux principes d’imagerie ou d’adapter les principes existants car la couleur n’est pas le seul attribut visuel exploité par les peintres : le brillant, le relief, la texture jouent aussi un rôle essentiel, en témoigne l’analyse en mars 2023 d’une toile de Pierre Soulages.

The PUMA beamline, created for the heritage community and accessible by all fields of science, welcomed its first users in 2019. Its optical layout uses a horizontal focusing mirror to prefocus the light emitted from the wiggler source for the experimental endstation. It provides a 5 µm × 7 µm microbeam for XRF, XAS, XRD and XEOL analysis or a wide 20 × 5 mm full field when the beam is defocused, and the KB mirrors are retracted. An extremely stable fixed-exit Si(111) monochromator is used to select the wavelength. Many experiments have been performed at PUMA, particularly in archaeology, paleontology, conservation, art history and in identifying safer conditions of irradiation for precious heritage samples. XRF analysis has been used, for example, to show the effects of the interaction of Palaeolithic ivory with soil; to identify the elemental composition of mineralized textiles and to reveal hidden morphologies of fossils.

Knowledge of the early evolution of post-Palaeozoic crinoids mainly relies on the well-preserved and abundant mate-rial sampled in Triassic Konservat-Lagerstatten such as those from the Anisian Muschelkalk (Middle Triassic) of the Germanic Basin. These crinoid-bearing Lagerstatten have been central to understanding the rapid evolution and diver-sification of crinoids after the dramatic Permian/Triassic Boundary biological crisis that led the class to near-extinction. The Encrinida are the emblematic crinoids of the Triassic. They are mainly known from rich fossil deposits where their abundant ossicles are at the origin of the extensive crinoidal limestone beds of the German Upper Muschelkalk. So far, they were first represented in the Middle Triassic by the family Dadocrinidae and genus Dadocrinus. In the present work, a new species Dadocrinus montellonis sp. nov., is described based on a well-preserved, almost complete articulated spec-imen from the Spathian (Lower Triassic) of Nevada (USA). The new species differs from other species ofDadocrinus by its palaeobiogeographic position but also by its earlier stratigraphic occurrence and ancestral morphology. It represents the first reported occurrence of Dadocrinus outside the Germanic Basin prior to the Middle Triassic and also the oldest firm evidence of its presence in the Early Triassic (middle-late Spathian). This discovery sheds new light on the origin of post-Palaeozoic crinoids. It suggests a much wider distribution than commonly assumed for the genus Dadocrinus and implies that the first dadocrinids originated either in the Panthalassa or Tethys oceans, and then dispersed over long distances in a relative short period of time.

In recent years, we have seen a significant increase in interest in the effects of irradiation used for analytical purposes on art, archaeological, palaeontological and palaeoenvironmental samples and objects. Among the main trends regarding ionising radiations used in X-ray, UV and ion beam experiments, we have observed a greater consistency in the description of the effects of irradiation, a number of quantitative studies, while several works studied in depth the corresponding chemical mechanisms and kinetics. We have also observed the development of analytical strategies and dedicated instruments to better detect and limit the effects of irradiation in real experiments on ancient samples and objects. Emerging trends include detailed mechanistic studies on specific systems, the development of statistical methods to reduce the doses required to study samples, and the development of early warning systems capable of feeding back into the experiment while an acquisition is in progress.

The peopling of the Americas and human interaction with the Pleistocene megafauna in South America remain hotly debated. The Santa Elina rock shelter in Central Brazil shows evidence of successive human settlements from around the last glacial maximum (LGM) to the Early Holocene. Two Pleistocene archaeological layers include rich lithic industry associated with remains of the extinct giant ground sloth Glossotherium phoenesis. The remains include thousands of osteoderms (i.e. dermal bones), three of which were human-modified. In this study, we perform a traceological analysis of these artefacts by optical microscopy, non-destructive scanning electron microscopy, UV/visible photoluminescence and synchrotron-based microtomography. We also describe the spatial association between the giant sloth bone remains and stone tools and provide a Bayesian age model that confirms the timing of this association in two time horizons of the Pleistocene in Santa Elina. The conclusion from our traceological study is that the three giant sloth osteoderms were intentionally modified into artefacts before fossilization of the bones. This provides additional evidence for the contemporaneity of humans and megafauna, and for the human manufacturing of personal artefacts on bone remains of ground sloths, around the LGM in Central Brazil.