Caracterización de materias primas y muestras cocidas de utilidad como búcaros

Se conocen por búcaros a aquellas vasijas de barro que además de refrescar y perfumar el agua eran apreciadas porque se comía trozos de ellos, una vez be bida el agua. Esta costumbre, buctmofagia, estaba muy extendida en España en tre los siglos XVI y XVII. Se han caracterizado química y mineralógicamente diversas materias primas y fragmentos cerámicos de posible utilidad como búcaros. Las materias primas proceden de Tierra de Barros, Badajoz, y las piezas cerámicas de España, Por tugal y México. Se han estudiado asimismo algunos cortes estratigráflcos y se han analizado mediante energías dispersivas de rayos X los pigmentos decorativos y por microespectrometría de infrarrojos los posibles compuestos orgánicos presentes en superficie. Se estudian asimismo los engobes y vidriados

Study of the dehydroxylation-rehydroxylation of pyrophyllite

Pyrophyllite is a raw material of significant interest due to its large number of applications. Most of these applications require a thermal transformation of pyrophyllite; this thermal transformation implies the release of structural OH groups and the formation of new phases. In this paper, we report on the dehydroxylation of pyrophyllite and the reversibility of the process. A value of 224±16 kJ/mol for the dehydroxylation of pyrophyllite was obtained. In addition, it was observed that the partially or totally dehydroxylated pyrophyllite suffered a partial reversible rehydroxylation when cooled to room temperature. This rehydroxylation was substantiated by thermogravimetric measurements, while infrared spectroscopic studies showed that, during the rehydroxylation, the intensity of the OH band at 3675 cm -1 increased as two new bands at 3690 and 3702 cm-1 appeared. This rehydroxylation process was heavily influenced by the particle size of the pyrophyllite. Thus, smaller particles (<1 μm) showed a larger rehydroxylation percentage (about 12%), while the larger ones (20-40 μm) showed a smaller percentage (about 1.6%). The extent of rehydroxylation also depended on the dehydroxylation temperature and reached a maximum value at 750°C.Ministerio de Economía y Competitividad 2008-06619/MATJunta de Andalucía TEP-0300

Scientific study of the Gothic-Renaissance altarpiece of Santiago church in Écija (Spain)

This work reports the characterization of inorganic and organic materials used for producing the polychrome of gothic-renaissance altarpiece of 16th century. The study was carried out in the cross sections prepared from small samples. Combined use of optical microscopy, micro-FTIR spectroscopy, SEM-EDX and XRD techniques has proved to be valuable for the characterization of compounds detected within artworks studied. Gypsum and animal glue animal support, casein and egg, lead oxide, gold and bole layers, iron oxides, red lake, cinnabar, white lead, cobalt smalt, azurite, tin-lead compounds were found. Red colours were obtained by a mixture of vermilion (HgS), and red lead (Pb3O4). A red lake was also added in some cases. Hematite was used mostly for the obtaining of violet colour, mixed with azurite in some cases or with smalt in other ones. Green colour was obtained with a mixture of azurite and tin-lead yellow with hydrocerussite and calcite. These pigments and the kind of binders were indicative of original materials or at least not recent interventionsPeer reviewe

A new approach to the determination of the synthetic or natural origin of red pigments through spectroscopic analysis

This work suggests a way of differentiation between the natural or synthetic origin of inorganic materials that were historically used in the Cultural Heritage field. An exhaustive review of different reported procedures of synthesis of pigments was conducted, as well as a review of the accompanying minerals in case of natural pigments. The natural or synthetic origin of the pigments studied in this work was performed through the characterization of the accompanying minerals, in the case of the natural pigments, or the trace elements that are present as part of synthesis by-products or washing/purifying reagents and/or reactants that have only been partly removed in the final steps of these processes. This work characterized red pigments due to their wide variety, complexity and possibility of use in different mixtures. The following pigments were studied: cinnabar-vermilion, red lead and iron pigments. Also mixtures of these pigments between them and with red lake were also studied. Natural cinnabar was accompanied by silicon oxide (opal, chalcedony or quartz), calcite, clay minerals and, sometimes, pyrite. K together with S indicated a synthetic pigment (vermilion) obtained through the wet method. Nevertheless, K has not been found in layers containing only vermilion in our samples. The presence of Sn in some cases indicated vermilion that came from the dry process. K from the synthesis always appeared in the red lead pigment. The red natural ochre was confirmed by presence of clay minerals and iron. It should be said that Ca and S, and sometimes Al and K, were usually found in Mars red pigment. The presence of Al and Ca allowed the identification of carmine lake.The financial support of the Ministerio de Economía y Competitividad, Secretaria de Estado de Investigación, Desarrollo e Innovación (BIA2014-55318-R) is also acknowledged

Study of the thermal decomposition of historical metal threads

In this work, it is reported that thermal analysis techniques such as differential thermal analysis and thermogravimetric analysis are very useful for evaluating metals threads and fibres used in the manufacture of historical artifacts. Thermal analysis has been used to characterize the silk, cotton and linen employed as supports and the copper, silver and aluminium as the metallic components in the studied threads. Other organic compounds, mainly added for the conservation of the threads, have also been characterized.The financial support of the Spanish Commission Interministerial of “Economia y Competitividad” (Plan Estatal 2013–2016 Retos–Proyectos I+D+i) under Project BIA2014-55318-R is also acknowledged

Study of the dehydroxylation-rehydroxylation of pyrophyllite

Pyrophyllite is a raw material of significant interest due to its large number of applications. Most of these applications require a thermal transformation of pyrophyllite; this thermal transformation implies the release of structural OH groups and the formation of new phases. In this paper, we report on the dehydroxylation of pyrophyllite and the reversibility of the process. A value of 224±16 kJ/mol for the dehydroxylation of pyrophyllite was obtained. In addition, it was observed that the partially or totally dehydroxylated pyrophyllite suffered a partial reversible rehydroxylation when cooled to room temperature. This rehydroxylation was substantiated by thermogravimetric measurements, while infrared spectroscopic studies showed that, during the rehydroxylation, the intensity of the OH band at 3675 cm -1 increased as two new bands at 3690 and 3702 cm-1 appeared. This rehydroxylation process was heavily influenced by the particle size of the pyrophyllite. Thus, smaller particles (<1 μm) showed a larger rehydroxylation percentage (about 12%), while the larger ones (20-40 μm) showed a smaller percentage (about 1.6%). The extent of rehydroxylation also depended on the dehydroxylation temperature and reached a maximum value at 750°C. © 2010 The American Ceramic Society.Peer Reviewe

Forgery detection on an Arabic illuminated manuscript by micro-Raman and X-ray fluorescence spectroscopy

An Arabic manuscript, supposed to be from the 14th century, was investigated and its components (pigments and dyestuffs) characterised using micro-Raman and X-ray fluorescence (XRF) spectroscopy, the latter employing a portable XRF/X-ray diffraction (XRD) system. The presence of anatase, rutile, calcite, barite, zinc oxide, carbon black, vermilion, hematite, goethite, β-naphthol, copper phthalocyanine, pigmosol green and a brass-based pigment was detected in the different zones of the illuminated manuscript. The detection of titanium oxides, barite and organic synthetic colourants such as β-naphthol and copper phthalocyanine and derived compounds provides indisputable indication of forging, repainting or retouching after the 19th century in the image of the manuscript. © 2010 John Wiley & Sons, Ltd.The authors acknowledge assistance from the C2RMF-AGLAE staff (especially Dr Jacques Castaing), English editing from one the reviewers and financial support from contracts MEC/FECYT 2007, JAE Doc 088, the program EU-ARTECH (FP6, European Union, contract RII3-CT-2004-506171) and the projects MAT2008-02008MAT (National I+D+I 008-2011) and P08-HUM04188 (Excellency).Peer Reviewe