Detecting recent forgeries of Impressionist and Pointillist paintings with high-precision radiocarbon dating.

We report on the capacity of AMS radiocarbon dating to play a decisive role in fighting against the illicit trade in art. In the framework of a current police investigation, where previously unseen paintings were discovered in a restorer's workshop by the French Central Office for the Fight against Illicit Trafficking in Cultural Property (OCBC), we demonstrated that two paintings alleged to be by Impressionist and Pointillist artists had in fact been painted recently. Our results were based on the excess of 14C derived from atmospheric nuclear tests detected in the fibers used to make the canvas. By combining AMS 14C absolute dating and the fine precision of the post-bomb atmospheric calibration curve, we established a clear chronological context for the production of these forgeries. 14C content of the fibers revealed that the canvases were manufactured in 1956-1957 or, more likely, after 2000. As a result, absolute dating proves unambiguously that the Impressionist and Pointillist paintings are forgeries since they were not painted at the beginning of the 20th century by the alleged artists, who died in the 1940s.

Development of a non-destructive methodology using ATR-FTIR and chemometrics to discriminate wild silk species in heritage collections.

This paper aims to develop a non-destructive methodology applicable to heritage artifacts in order to discriminate between different species of wild silks. Wild silks are less known than domestic silk from Bombyx mori, but they are numerous and have been used in textile weaving for thousands of years. Archaeological artifacts, museum artifacts, and ethnographic collections deserve to be better documented regarding wild silks. The developed methodology is based on Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR-FTIR) coupled with chemometric analyses such as Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA). Discriminant statistical analysis has enabled within a corpus of wild silks, including cocoons from the collections of the musée du quai Branly-Jacques Chirac (Paris, France), to differentiate cocoons of the species Borocera madagascariensis (Lasiocampidae) from samples belonging to the Saturniidae family. These very encouraging results are promising for future studies involving more species and more diverse artifacts.

In-place molecular preservation of cellulose in 5,000-year-old archaeological textiles.

The understanding of fossilization mechanisms at the nanoscale remains extremely challenging despite its fundamental interest and its implications for paleontology, archaeology, geoscience, and environmental and material sciences. The mineralization mechanism by which cellulosic, keratinous, and silk tissues fossilize in the vicinity of archaeological metal artifacts offers the most exquisite preservation through a mechanism unexplored on the nanoscale. It is at the center of the vast majority of ancient textiles preserved under nonextreme conditions, known through extremely valuable fragments. Here we show the reconstruction of the nanoscale mechanism leading to the preservation of an exceptional collection of ancient cellulosic textiles recovered in the ancient Near East (4,000 to 5,000 years ago). We demonstrate that even the most mineralized fibers, which contain inorganic compounds throughout their histology, enclose preserved cellulosic remains in place. We evidence a process that combines the three steps of water transport of biocidal metal cations and soil solutes, degradation and loss of crystallinity of cellulosic polysaccharides, and silicification.

Unraveling the polychromy and antiquity of the Pachacamac Idol, Pacific coast, Peru.

Pachacamac is the name of the 15th-16th century Inca sanctuary on the Peruvian coast as well as the name of one of the principal oracles of Inca divinities. This effigy would have been destroyed by Pizarro in 1533 during his visit to the great monumental complex, and as such the originality and antiquity of the wooden statue-the so-called Pachacamac Idol-have been the subject of much controversy and debate. We present here previously unpublished dates that confirm its manufacture during the Middle Horizon (AD 500-1000), as well as evidence of its original polychromy. Traces of colors were observed on its different sections with portable microscopy and analyses with two different X-Ray Fluorescence spectrometry techniques, leading to identification of yellow, white, and red mineral pigments, including the presence of cinnabar. Dated between the 8th and 9th centuries, the statue would have been worshipped for almost 700 years, from the time of its creation to the time of the Spanish conquest, when Pachacamac was a major place of pilgrimage. These data not only offer a new perspective on Pachacamac's emblematic sacred icon, but also on the colorful practices of the Pre-Hispanic Andes.

Synchrotron-Based Phase Mapping in Corroded Metals: Insights from Early Copper-Base Artifacts.

The detailed description of corrosion processes in ancient and historical metal artifacts currently relies on the in-depth study of prepared cross sections. The in-plane elemental and phase distributions can be established from a combination of light and electron microscopy characterization. Here, we show that high-resolution virtual sectioning through synchrotron X-ray microcomputed tomography allows a precise noninvasive 3D description of the distribution of both internal and external mineral phases in whole objects. In fragments of early copper artifacts (third-second millennium BC) from Southern Mesopotamia and the Indus valley, this approach provided essential clues on long-term corrosion processes. Major and minor phases were identified through semiquantitative evaluation of attenuation coefficients using polychromatic X-ray illumination. We found evidence for initially unidentified phases through statistical processing of images. We discuss interpretation of the distribution of these phases. A good correlation between the corrosion phases identified by CT and by invasive BSE-SEM is demonstrated. In addition to the stratigraphy of the copper corrosion compounds, we examine and discuss the variations observed in the attenuation coefficients of Cu(I) phases. Semiquantitative synchrotron X-ray microtomography phase mapping requires no specific sample preparation, in particular polishing or surface finishing, and any material tearing or displacement is avoided. We also provide evidence for the noninvasive observation of phases rapidly altered upon preparation of real cross sections. The method can be applied when cross-sectioning even of minute fragments is impossible.

The embalmed heart of Richard the Lionheart (1199 A.D.): a biological and anthropological analysis.

During the Middle Ages, the partition of the cadaver of the elite members was a current practice, with highly technical treatment given to symbolic organs such as the heart. Considered mostly from a theoretical point of view, this notion of dilaceratio corporis has never been biologically explored. To assess the exact kind of embalming reserved to the heart, we performed a full biomedical analysis of the mummified heart of the English King Richard I (1199 A.D.). Here we show among other aspects, that the organ has been embalmed using substances inspired by Biblical texts and practical necessities of desiccation. We found that the heart was deposed in linen, associated with myrtle, daisy, mint, frankincense, creosote, mercury and, possibly, lime. Furthermore, the goal of using such preservation materials was to allow long-term conservation of the tissues, and good-smelling similar to the one of the Christ (comparable to the odor of sanctity).