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Ager F.J.,University of Seville | Gomez-Tubio B.,University of Seville | Paul A.,University of Seville | Gomez-Moron A.,Instituto Andaluz Of Patrimonio Historico | And 3 more authors.
Microchemical Journal | Year: 2016

Archaeological silver-copper alloys are usually affected by silver enrichment of the near surface layers, either intentional or fortuitous. In previous studies we have shown that surface composition of archaeological bronzes and leaded copper coins obtained by XRF can be corrected by means of gamma-ray transmission (GRT) to obtain the bulk composition. In the present work, we have studied the applicability of this method to silver-copper alloys and established the most suitable conditions for the GRT correction calculation. The analysis of the microstructure of the core and the corrosion layers of a set of silver roman coins shows that copper could be leached from the surface during corrosion and cleaning treatments, resulting in an apparent silver surface enrichment. After the correction calculations by GRT method, the concentrations of the major elements, Ag and Cu, were found to be in good agreement with the bulk composition obtained by direct analysis of the cut cross-sections of the coins. The GRT method shows to be a useful tool to study metal artefacts having a surface composition modified by corrosion or cleaning treatments. © 2015 Elsevier B.V.. Source


Alonso C.,Instituto Andaluz Of Patrimonio Historico | Gracia F.J.,University of Cadiz | Rodriguez-Polo S.,University of Cadiz | Martin Puertas C.,German Research Center for Geosciences
Cuaternario y Geomorfologia | Year: 2015

The bay of Cádiz is a coastal area intensively occupied during prehistorical and historical times from which many archaeological remains have been preserved. The bay is a low coast characterized by several spit-barrier systems which close wide estuarine marshes. This kind of coastal environment is especially vulnerable to marine energetic events, like storms and tsunamis, which have occurred in the region during the late Holocene with some regularity. The present work summarizes the different morphosedimentary records of historical marine events identified in the Bay up to date. New chronological and stratigraphical data are presented, obtained from drills, together with different geoarchaeological indicators of historical marine events identified along the Bay. Special attention is paid on the effects produced on the Valdelagrana spit-barrier, where the geometry and age of different historical beach ridges reveal the onset of at least three very energetic events, probably of tsunamigenic origin: one on 2700-2300 cal BP, a second one by the end of the IX century AD and the third one in 1755 AD. The two first events caused deep geomorphological modifications, like river captures, onset of new beach ridge systems, and coastal lowering. Archaeological data indicate that economical effects and infrastructure damage produced by these events conditioned later human occupation and related activities. © 2015, Asociacion Espanola para el Estudio del Cuaternario (AEQUA). All rights reserved. Source


Ortiz P.,Pablo De Olavide University | Antunez V.,Pablo De Olavide University | Ortiz R.,Pablo De Olavide University | Martin J.M.,Pablo De Olavide University | And 3 more authors.
Applied Surface Science | Year: 2013

The removal of unwanted matter from surface stones is a demanding task in the conservation of cultural heritage. This paper investigates the effectiveness of near-infrared (IR) and ultraviolet (UV) laser pulses for the cleaning of surface deposits, iron oxide stains and different types of graffiti (black, red and green sprays and markers, and black cutting-edge ink) on dolomitic white marble. The performance of the laser techniques is compared to common cleaning methods on the same samples, namely pressurized water and chemical treatments. The degree of cleaning achieved with each technique is assessed by means of colorimetric measurements and X-ray microfluorescence. Eventual morphological changes induced on the marble substrate are monitored with optical and electronic microscopy. It is found that UV pulsed laser ablation at 266 nm manages to clean all the stains except the cutting-edge ink, although some degree of surface erosion is produced. The IR laser pulses at 1064 nm can remove surface deposits and black spray acceptably, but a yellowing is observed on the stone surface after treatment. An economic evaluation shows that pulsed laser cleaning techniques are advantageous for the rapid cleaning of small or inaccessible surface areas, although their extensive application becomes expensive due to the long operating times required. © 2013 Elsevier B.V. All rights reserved. Source


Moreno-Suarez A.I.,University of Seville | Ager F.J.,University of Seville | Rodriquez-Segovia C.,Instituto Andaluz Of Patrimonio Historico | Gomez-Moron A.,Instituto Andaluz Of Patrimonio Historico | And 5 more authors.
Spectrochimica Acta - Part B Atomic Spectroscopy | Year: 2016

Archeological pieces with high Ag concentrations often have a surface enrichment of Ag. Usually, researchers in this field do not agree on the causes of these enrichments, one of which could be the cleaning procedures. In this work, a set of 18 ancient Greek silver coins was selected to study the effects of different cleaning procedures in terms of producing a surface Ag enrichment. The aim of this study is to find and select the less aggressive one in terms of the lower modification of Ag concentrations and visual aspect. These coins were analyzed by X-ray fluorescence (XRF) before and after each cleaning procedure. © 2015 Elsevier B.V. All rights reserved. Source

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