Analysis of pigments in polychromes by use of laser induced breakdown spectroscopy and Raman microscopy

Ochres were the most common source materials for pigments used in Palaeolithic rock art paintings. This work analyses the petrographic and geochemical signatures of different ochre samples from outcrops inside Tito Bustillo Cave and the Monte Castillo Caves using the most common techniques (petrography, XRD, SEM-EDS and ICP-MS) in archaeological pigment characterization studies. The results obtained permit the identification and characterization of the different source ochre types and, furthermore, allow the establishment of mineralogical and geochemical proxies for the study of questions related to ochre characterization, formation processes and provenance.

The origin and geochemical characterization of red ochres from the tito bustillo and monte castillo caves (northern spain)

There is a clear need to de velop and systematise a methodology to approach interventions on ancient renders. In fact inadequate interventions, with systematic resource to modern solutions, originated in Portugal a situation characterised by the disappearing of original lime renderings and finishings and caused several anomalies due to functional incompatibility between pre-existing elements and new materials. The research project Oldrenders, accomplished by researchers from LNEC in collaboration with the construction enterprise STAP - Reparacao, Consolidacao e Modificacao de Estruturas, SA., and partially financed by Agencia de Inovacao , has as main objectives the definition of such a methodology and the preparation of criteria to support the selection of substitutive compatible mortars. This paper synthesises the aims and conclusions of the Project. 1. OBJECTIVES OF THE RESEARCH Interventions on ancient buildings included for too long the systematic remotion of the original renders, plasters and finishings and its substitution by render s and plasters based on Portland cement, painted with products based, first in oil paints and then in acrylic and vinylic resins. In the meantime, the theory of conservation has more and more pointed out the historic and aesthetic importance of preservati on of material evidences and their fundamental part in the definition of formal and material authenticity of historic artifacts.

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Methodologies for characterisation and repair of mortars of ancient buildings

We present a new multi-analytical approach to the characterization of black pigments in Spanish Levantine rock art. This new protocol seeks to identify the raw materials that were used, as well as reconstruct the different technical gestures and decision-making processes involved in the obtaining of these black pigments. For the first of these goals, the pictorial matter of the black figurative motifs documented at the Les Dogues rock art shelter (Ares del Maestre, Castellon, Spain) was characterized through the combination of physicochemical and archeobotanical analyses. During the first stage of our research protocol, in situ and non-destructive analyses were carried out by means of portable Energy Dispersive X-Ray Fluorescence spectrometry (EDXRF); during the second stage, samples were analyzed by Optical Microscopy (OM), Raman spectroscopy, and Scanning Electron Microscopy coupled with Energy Dispersive X-ray spectroscopy (SEM-EDX). Two major conclusions have been drawn from these analyses: first, charred plant matter has been identified as a main component of these prehistoric black pigments; and second, angiosperm and conifer charcoal was a primary raw material for pigment production, identified by means of the archaeobotanical study of plant cells. For the second goal, black charcoal pigments were replicated in the laboratory by using different raw materials and binders and by reproducing two main chaines operatoires. The comparative study of the structure and preservation of plant tissues of both prehistoric and experimental pigments by means of SEM-EDX underlines both a complex preparation process and the use of likely pigment recipes, mixing raw material with fatty or oily binders. Finally, the formal and stylistic analysis of the motifs portrayed at Les Dogues allowed us to explore the relationship between identified stylistic phases and black charcoal pigment use, raising new archaeological questions concerning the acquisition of know-how and the transfer of traditionally learned chaines operatoires in Spanish Levantine rock art.

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Identification of plant cells in black pigments of prehistoric Spanish Levantine rock art by means of a multi-analytical approach. A new method for social identity materialization using chaîne opératoire.

This work explores the use of multispectral imaging (MSI) techniques applied to the investigation of Late Antique (c. 250-800 AD) textiles found in Egypt. Although the use of these techniques is well-established in the study of polychrome surfaces, they have only been sparingly and often unsystematically applied to the investigation of textiles. The aim of this work is therefore to bridge this gap by showing how this non-invasive, relatively inexpensive and portable methodology can be used to map the photoluminescence and reflective characteristics of textiles under different wavelengths of light, and to provide qualitative and holistic insights into the chemical nature of the materials that compose them. Standardised acquisition and post-processing methods were applied to produce visible-reflected (VIS), ultraviolet-induced visible luminescence (UVL), infrared-reflected (IRR), infrared-reflected false colour (IRRFC), ultraviolet-reflected (UVR) and ultraviolet-reflected false colour (UVRFC) images that provided preliminary indications of the colourants used and their spatial distribution. This proved to be an important aid in planning more targeted and effective sampling strategies and facilitated comparisons between objects. Visible-induced visible luminescence (VIVL) and multiband-reflected (MBR) imaging were also explored for the first time with application to textiles, demonstrating their potential in mapping red and blue colourants respectively. The physical properties observed from all of these images were then related to the more detailed information provided by complementary non-invasive techniques, such as fibre optic reflectance spectroscopy (FORS), and micro-invasive approaches, such as high-performance liquid chromatography mass spectrometry (HPLC-MS). Guidelines towards the interpretation of complex MSI images and a discussion of the potential and limitations of relating multispectral data to chemical properties are presented. An important result of this work is the delineation of a protocol, which combines optical microscopy (OM), MSI, FORS and HPLC-MS and shows a high degree of potential, not only for the investigation of Late Antique textiles but for textiles in museum and historic collections generally.

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A multispectral imaging approach integrated into the study of Late Antique textiles from Egypt.

Examen científico aplicado a la conservación de obras de arte

Pure gold is a soft, malleable, and ductile metal. These characteristics allow it to be hammered into thin leaves and applied to other surfaces, a process known as gilding. This study examines the gilding techniques used in Spanish panel and retable painting from the fifteenth to early sixteenth century, considering gold’s intrinsic value and symbolism as well as its role as a painting material. First, historical references and laboratory analyses of panel paintings will be compared and interpreted; second, important technical aspects of gold leaf will be discussed, including its composition and possible origin, its thickness and size, its price, and the different poliments and modes of adhesion used to apply it to the substrate.

Gilding in Spanish panel painting from the fifteenth and early sixteenth centuries

Estudio de la policromía y patinas de los relieves del claustro del Monasterio de Santo Domingo de Silos (Burgos)

Resultados analíticos obtenidos en el estudio de pigmentos y posibles materiales colorantes de las pinturas de la Cueva de Tito Bustillo

La madera y la piedra han sido los materiales más comunes empleados por los artistas para realizar objetos tridimensionales que posteriormente se policromaban. La policromía, ilumina las formas de las figuras y busca un efecto de realismo, unas veces, de fantasía, otras, que varía también con la iconografía, la función de la obra, etc. Su estética propia es inseparable de la de la escultura y está sujeta a la evolución técnica y estilística de los diferentes períodos de la historia del arte. Además, hay otros materiales fundidos, tallados o modelados, de origen inorgánico —como los metales, la terracota, el yeso y el estuco—, u orgánico —como el marñl, el cuero y las fibras vegetales recubiertas de papel o papelón—, que pueden presentar una policromía completa o parcial .̂ La escultura, por ser tridimensional y estar conformada mediante volúmenes, suscita problemas relativos a la materia constitutiva del material tallado, modelado o fundido, y al desigual desgaste de sus diferentes zonas. Si además está policromada, hay que atender al de-

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María Luisa Gómez González

Papers

Examen científico aplicado a la conservación de obras de arte

Gilding in Spanish panel painting from the fifteenth and early sixteenth centuries

Estudio de la policromía y patinas de los relieves del claustro del Monasterio de Santo Domingo de Silos (Burgos)

Resultados analíticos obtenidos en el estudio de pigmentos y posibles materiales colorantes de las pinturas de la Cueva de Tito Bustillo

Diagnóstico y metodología de restauración en la escultura policromada