Jorge Ordaz

Airborne particulate matter around the Cathedral of Burgos (Castilla y León, Spain)

A methodology to collect and analyse atmospheric particulate matter has been developed at the Cathedral of Burgos (Spain). Particles were collected in a portable particle sampler on carbon layers and stone surfaces. The analyses were undertaken under SEM-EDX by means X-ray mapping and Featurescan (a program for the automated characterisation of particles). To determine their possible sources, particles collected in the sampler and on carbon layers were classified according to their composition, mainly by cluster analysis. Then, they were compared with those deposited on stone surfaces. This classification is useful when a plan of preventive conservation for monuments is to be undertaken. In general, no important differences are observed between the chemical composition of particles directly collected from the atmosphere and those deposited on different substrates. Fine particles present the highest sulphur contents (almost 100%), while calcium is the major element in the medium and coarse particles. Other abundant elements are silicon, chlorine and phosphorus. The number of iron-rich particles is small. The study of the material deposited on carbon layers and stone substrates has confirmed the presence of gypsum in all cases.

Laser cleaning of stone materials: an overview of current research

Abstract This paper presents an overview of current knowledge and recent advances in the application of pulsed laser radiation to the cleaning of works of art, particularly ornamental stone. Special emphasis is put on the critical review of publications from the last six years. The recent history of laser cleaning in art conservation is summarised and a description of laser fundamentals, laser types and practicalities for use in conservation is given. Existing explanatory models of the underlying physics of laser cleaning are briefly described, as are the advances in laser cleaning of different stone types. Common techniques, including on-line monitoring used to detect material damage after laser irradiation, are outlined and examples are given of their application. Finally, current trends and improvements in laser-cleaning efficiency and the reduction of damaging side effects are addressed. It is hoped that this overview will bring greater attention to the issues that are important for future research on the laser cleaning of stone.

La petrofísica en la interpretación del deterioro y la conservación de la piedra de edificación

Entre la importante coleccion de fosiles que guarda el Museo del Departamento de Geologia de la Universidad de Oviedo, procedentes principalmente de la cordillera Cantabrica, se destaca en este trabajo el material tipo (holotipo y paratipos) de 55 especies de braquiopodos carboniferos. Se mencionan el holotipo y paratipos de estas especies (7 de ellas son, a su vez, especies tipo de sus respectivos generos, y uno de estos ultimos es el genero tipo de una subfamilia), se indica su procedencia y edad, asi como la sinonimia correspondiente y se figura el holotipo. Se destaca la importancia de esta vertiente ligada a la investigacion y la obligacion que tiene la institucion de conservar, catalogar adecuadamente y poner este material a disposicion de la comunidad cientifica.

ULTRASONIC VELOCITY AND HUMIDITY IN MONUMENTAL STONES

The velocity of propagation of ultrasonic waves in three sedimentary rock types, with different petrographical and physical properties, has been studied in relation to water content. The rocks investigated were a dolomite, a limestone and a sandstone used in the Cathedrals of Leon, Seville and Salamanca respectively. The objective was to determine the variation in the propagation velocity of waves under different conditions of water saturation. The technique can also be used to determine indirectly the water content of the rocks studied.

Reactivity of laser-cleaned stones to a SO 2 ageing test

Con el fin de estudiar la reactividad o susceptibilidad frente a un ambiente contaminado de piedras limpiadas con radiacion laser Nd:YAG, se ha sometido una serie de materiales rocosos cementados (calizas) y cristalinos (marmol, granito) a un ensayo de exposicion a atmosfera concentrada en dioxido de azufre. Los efectos producidos en las muestras ensayadas se han valorado en funcion de las variaciones en la morfologia superficial, en el peso y en el color. Se concluye que la aplicacion de radiacion laser a las muestras de piedra seleccionadas no influye, de manera significativa, en la reactividad de estas frente al dioxido de azufre.

Relaciones entre porosidad, contenido en arcillas y durabilidad de areniscas

Se realiza la caracterización petrográfica de tres variedades de areniscas procedentes de Villamayor (Salamanca), Somió y Tazones (Asturias), poniendo de relieve la significación que el porcentaje y tipo de arcillas que cementan los granos minerales tiene, en estos casos concretos, en la configuración del sistema poroso. Asimismo, se correlacionan estas características con la durabilidad de dichas areniscas, evaluada mediante ensayos de heladicidad y cristalización de sales. R. M. ESBERT; J. ORDAZ; L. VALDEON Departamento de Petrología y Geoquímica Facultad de Geología. Universidad de Oviedo