Floréal Daniel

Symbolic use of marine shells and mineral pigments by Iberian Neandertals

Two sites of the Neandertal-associated Middle Paleolithic of Iberia, dated to as early as approximately 50,000 years ago, yielded perforated and pigment-stained marine shells. At Cueva de los Aviones, three umbo-perforated valves of Acanthocardia and Glycymeris were found alongside lumps of yellow and red colorants, and residues preserved inside a Spondylus shell consist of a red lepidocrocite base mixed with ground, dark red-to-black fragments of hematite and pyrite. A perforated Pecten shell, painted on its external, white side with an orange mix of goethite and hematite, was abandoned after breakage at Cueva Antón, 60 km inland. Comparable early modern human-associated material from Africa and the Near East is widely accepted as evidence for body ornamentation, implying behavioral modernity. The Iberian finds show that European Neandertals were no different from coeval Africans in this regard, countering genetic/cognitive explanations for the emergence of symbolism and strengthening demographic/social ones.

Hyperspectral imaging, spectrofluorimetry, FORS and XRF for the non-invasive study of medieval miniatures materials

BackgroundIlluminated manuscripts are complex multi-layer and multi-material objects. To this difficulty, from the analytical point of view, is added the impossibility of removing samples from these paintings for the study of their materials and techniques. There are relatively few analytical methods that satisfy these constraints as the availability of non-invasive techniques adapted to painted manuscripts is limited and mainly focused on the characterization of inorganic compounds. In the context of a research project on the analytical study of the forty miniatures in the Marcadé collection (Treasury of the Saint-André Cathedral of Bordeaux, XIII to XVI century), the potential of two non-invasive methods, hyperspectral imaging (HSI) and spectrofluorimetry is explored.ResultsThe methodological development of these techniques as well as preliminary tests on miniatures recreated according to medieval recipes and materials, allowed the validation of the analytical parameters and the creation of a database of reference spectra (parchments, pigments, binders). Hyperspectral imaging associates reflectance spectra with each pixel of the image and treats the signal received in various wavelengths. The characteristics of the spectral signal in VIS range or NIR are used to get an identification and a localization of the components. It allows the study of the entire image and offers lots of ways to work: comparison of spectra, mapping, principal component analyses and false color images. Spectrofluorimetry is a sensitive method which gives information on fluorescent organic compounds under UV or visible light. Emission and excitation spectra of five red pigments in binding media have been collected. These methods were compared with X-ray fluorescence spectrometry for the qualitative analysis and mapping of the inorganic elements in a facsimile which had been purposely reproduced by an illumination painter who worked with original medieval recipes for the sake of developing the present study.ConclusionsThe combination of all these techniques allows good identification of all the materials used on an illuminated manuscript. The pertinent selection of the wavelengths used with the HSI system and a preliminary database and study of materials under UV and white light is described in this paper.

Hyperspectral imaging for the study of two thirteenth-century Italian miniatures from the Marcadé collection, Treasury of the Saint-Andre Cathedral in Bordeaux, France

Abstract Illuminated manuscripts are complex multi-layered and multi-material objects which include a support, preparatory layer, pigment layers, and often highlights. During research into a collection of medieval miniatures (Marcadé collection, Treasury of the Saint-Andre Cathedral in Bordeaux, France) dating from the thirteenth to the sixteenth centuries, two Italian illuminations were studied using hyperspectral imaging. This technique associates reflectance spectra with each pixel of the image. The characteristics of the spectral signal in the visible range are used to map pigments comparing reflectance spectra obtain with those of our reference library of medieval pigments. The exploitation of the data cube of the hyperspectral imaging was completed by point analyses such as Raman and X-ray fluorescence spectroscopy commonly used for the identification of pigments. A methodological development as well as preliminary tests on models made according to medieval recipes and materials (parchments, pigments, and binders, alone and combined together), allowed the validation of the analytical parameters and the development of a database of reference spectra. In the two Italian miniatures, the palette was identified and corresponds to typical medieval pigments as lapis lazuli, red lead, lead white, green copper-based pigment, and probably anthraquinone-based pigments such as brazilwood and kermes. Gold foil gilding decorates the corners of the images.

Gilding Techniques in Mural Paintings: Three Examples from the Romanesque Period in France

Since paleo-Christian times, gold maintains a close relationship with colour within the church. However, more than just colour, gold is also matter and light. It is heat, weight and density. The use of the precious metal has an artistic, aesthetic, political and liturgical function: it is a sign, mark, and symbol of power and authority.

Comparison between non-invasive methods used on paintings by Goya and his contemporaries: hyperspectral imaging vs. point-by-point spectroscopic analysis

The development of non-invasive techniques for the characterization of pigments is crucial in order to preserve the integrity of the artwork. In this sense, the usefulness of hyperspectral imaging was demonstrated. It allows pigment characterization of the whole painting. However, it also sometimes requires the complementation of other point-by-point techniques. In the present article, the advantages of hyperspectral imaging over point-by-point spectroscopic analysis were evaluated. For that purpose, three paintings were analysed by hyperspectral imaging, handheld X-ray fluorescence and handheld Raman spectroscopy in order to determine the best non-invasive technique for pigment identifications. Thanks to this work, the main pigments used in Aragonese artworks, and especially in Goya’s paintings, were identified and mapped by imaging reflection spectroscopy. All the analysed pigments corresponded to those used at the time of Goya. Regarding the techniques used, the information obtained by the hyperspectral imaging and point-by-point analysis has been, in general, different and complementary. Given this fact, selecting only one technique is not recommended, and the present work demonstrates the usefulness of the combination of all the techniques used as the best non-invasive methodology for the pigments’ characterization. Moreover, the proposed methodology is a relatively quick procedure that allows a larger number of Goya’s paintings in the museum to be surveyed, increasing the possibility of obtaining significant results and providing a chance for extensive comparisons, which are relevant from the point of view of art history issues.

Mobile hyperspectral imaging for the non-invasive study of a mural painting in the Belves Castle (France, 15th C).

Abstract Art History and the conservation of paintings require knowledge of the artist’s materials used, such as pigments, binders and preparatory layers. This information can also provide insight into the artist’s working methods. In recent years, research carried out mostly on paintings has proved that imaging spectroscopy techniques can be used efficiently for material identification and for mapping on artworks. The development of such in situ tools capable of examining the entire surface of a painting is of interest to the fields of history of art techniques and conservation In the context of a research project on the analytical study of the mediaeval mural painting in the Belves Castle (XV century), the potential of a new mobile system for hyperspectral imaging is explored. The pigments identified on the Belves mural paintings correspond to “classic” materials used in medieval times (red lead, red ochre, calcite and carbon black). From the methodologic point of view, the combination of methods has shown its efficiency. HSI allows a global vision and mapping of the pigments; point methods (Raman, EDXS) complete the results of reflectance spectra data.

Pigments & dyes in a collection of medieval illuminations (14th–16th century)

The Marcade Collection (Bordeaux Cathedral treasury) consists among other objects of 42 illuminations (14th to the 16th century) from five origins (France, Italy, Germany, the Netherlands, and Spain). For better knowledge of these miniatures, the pigments and dyes have been analyzed in ten illuminations chosen in order to represent the diversity of the collection. The aim of this study is to establish a panorama of the pigments and techniques used in medieval miniatures through the study of a set of manuscripts and to discuss the potentialities of the analytical techniques in order to reach this objective. Hyperspectral imaging is a rapid, mobile and noninvasive technique. It gives reflectance spectra for each pixel of the image. The datacube obtained was treated in order to visualize images and reflectance spectra. The software allows the mapping of the pigments by comparing spectra with those of our database. As some interpretation difficulties can appear for dyes or mixtures, to confirm the identification, point techniques such as Raman, X-ray spectroscopy, and Fiber Optic Reflectance Spectroscopy in the Near Infrared range were used. Analyses allowed access to the palette for each illumination and showed the colours diversity and pigments treatment. They increase knowledge about the materials used and the evolution of them during the time period: the use of dyes and shell gold became more important at the end of the period. The analytical choice respects the fragility and preciousness of these artworks and helps the fast data acquisition for the materials identification.

Probing some organic ukiyo-e Japanese pigments and mixtures using non-invasive and mobile infrared spectroscopies

Non-invasive identification of organic colourants in paintings still remains a challenging issue, especially in the case of extremely thin layers of paint on printed paper such as Japanese ukiyo-e prints. Because prints are fragile artworks, various non-invasive analytical methods need to be employed. The present work focuses on results obtained by combining fibre optic reflectance spectroscopy in the near-infrared range (FORS NIR) with mid-infrared (MIR) spectroscopy. The first step consists of identifying spectroscopic marker bands typical of some organic pigments (indigo, gamboge, cochineal, turmeric, safflower, dragon’s blood). Some reference printouts involving paper substrate, binder and pigments (seldom used or as mixtures) were then investigated in order to establish a straightforward way to extract the marker bands of the pigments. Some data post-treatments were applied to the spectra, such as spectral subtraction, in order to abstract the signal from overlapping bands originating from both substrate and binder, and second derivative calculation to emphasise the pigment marker bands’ frequency positions. These data treatments turned out to be relevant to extract information on the organic pigments of interest, even within complex mixtures.