Interpretación de los valores de microdureza de la recta de Gahm. Aplicación del método al estudio de la dureza de la hematites y de la cobaltina

The description of how to obtain the experimental data of the hardness at microscopical scale in hematites and cobal- tirie and of the respective equipments used is given. The graphics of the data obtained are exposed according to Gahm, to obtain the best straight line. The conclusions and recomtnendations on doing the research work on the hardness of the minerals, are stablished

Estudi de les constants òptiques del carbur de silici entre 400 i 1100 nm

The silicon carbide has a capital importance as oficial standard for photometric measurements. For this reason, the correct calibration of its optical constants is very important in the quantitative microscopy field. The experimental dispersion curves of the reflectance in air and oil by direct method are obtained. The n and k optical constants from 400 to 1.100 nm are also calculated

Are patinas of the Mediterranean monuments really related to the rock substrate?

Patinas of different mineralogies and colours occur on most monuments of the Mediterranean area. The origin(s) of the latter have often been related to previous painting and/or protective treatment(s). Microbial and biogeochemical pathways of formation, however, have as well been proposed and discussed. Paintings and photographs make it clear that coatings of changing colours have covered famous monuments in the past 200 years. Also the presence of microbiota has been recorded already 150 years ago. The work recorded here was done on several buildings in the Mediterranean area. A wide variety of localities and rock substrates and the patinas on them have been studied. Among the rocks were marbles, limestones calcarenites, granites and sandstones. In all cases studied patinas, their thickness and colour as well as their mineralogical composition were related to the exposure type. The patinas usually are multi-layered, the individual layers characterized by different crystal size, texture, mineralogy, and colour. Orange to grey layers are characterized by calcium carbonates and oxalates with some phosphates admixed, while the dark grey to black layers are rather characterized by gypsum with some trapped air-borne particles in cases. The petrology and mineralogy of the patinas is practically identical in all cases. Many of the patinas are inhabited by a variated microflora causing pitting and exfoliation in cases of the patina. Sometimes the pitting is only seen in the patina, and it reaches also the bedrock. A relationship between patina formation, preservation, destruction and climatic changes over the past 200 years is derived from these findings

Medida de reflectancias en inmersión en aceite mediante el método directo y cálculo de n y k de 400 a 1100 nm.

Se ha centrado el problema en las mediciones en aceite en el directo para calcular n y k. Para ello se ha colocado una gota de aceite que se mantiene en contacto con la muestra mediante un cubreobjetos. Éste provoca una reflectancia adicional (efecto glare) que es necesario corregir. Se plantea el desarrollo matemático para esta corrección, y se realizan las comprobaciones con un sistema estándar

Characterizing paint technologies and recipes in Levantine and Schematic rock art: El Carche site as a case study (Jalance, Spain)

This paper contributes to current debates on the technologies and practices of prehistoric artists using the rock art site of el Carche (Jalance, Spain) as a case study. The site preserves both Levantine and Schematic paintings, yet poorly understood from an analytical point of view. In the past, it has even been argued how little differentiation there is between these two post-Paleolithic traditions in terms of paint composition. Our aim with this paper was to identify pigments, paint recipes and technologies and decipher the order of the superimpositions, both between Levantine motifs of different styles, and between these and the Schematic ones. To do so, we adopted a multi-stage and multi-technical analytical strategy, trying to find a balance between sound scientific investigation and impact on the art, considering the irreplaceable nature of this World Heritage rock art. As such, our approach begins with in situ non-invasive investigations using portable EDXRF, to then collect micro-samples for non-destructive analyses by means of Optical Microscopy, Scanning Electron Microscopy coupled with Energy Dispersive X-Ray Spectroscopy (SEM-EDX), micro-Raman Spectroscopy and Fourier Transform Infrared Spectroscopy (FTIR). One of the key highlights of these paper is the identification of up to four different paint compositions, produced with various hematite-based raw materials and different processing techniques. This variability had not been previously documented. Interestingly though, no direct correlations appear to exist between styles or sub-styles and recipes. Some of these paint mixtures were even shared by both traditions. These results are discussed in cultural terms, challenging previous interpretations suggesting a similar pigment composition between Levantine and Schematic art. Microstratigraphic analysis of the cross-sections only partially clarified the overlapping sequence unveiling the complexity of these analysis. They also revealed several degradation layers and external crusts related to rock alteration processes and biological formations. Their role in rock art conservation is also discussed

Proceso automático para la medida de las reflectancias. 1.- Descripción preliminar

To calculated the physical constant, n, k, from the reflectance measurements in two different media of known refractive indices, it is necessary to apply a stadistic criterion that represents to obtein a great numher of experimental data. The preliniinary description of the method used shows how et is simplified the calculation of the values of n, k, from the experimental data of reflectance

Caracterización de los lignitos Garumnienses del Pirineo Central catalán

La Formación Tremp en los sectores de Berga, Tremp y Ager (Pirineo) presenta materia orgánica de tipo húmico, procedente de plantas terrestres y con una amplia variabilidad de resinita. Asociada a ella rellenando cavidades celulares, reemplazando o alternando en bandas se encuentra la fracción mineral, siendo mayoritariamente carbonática. El dominio de una fracción u otra está directamente relacionada con el momento de sedimentación y el ambiente deposicional

La decoració de reflex metàl·lic: Un nanocompòsit medieval

Metallic reflection in decoration: a medieval nanocomposite.Decoration using metallic reflection is a technology that was developed in the 9th Century in the Middle East, from where the Muslim world spread, arriving in the Iberian Peninsular in the 13th century. By the 14th century the Craftsmen had reached the Aragon kingdom, and by the 15th century this technology had also arrived in Italy. The recent characterization of antique pieces of ceramic decorated in this way, as well as of modern reproductions, has shown that the metallic reflection is due to the formation of prime layers of silver and copper nanoparticles in the glazing. In this article we describe the key points of this nanotechnology developed by medieval craftsmen, via trial and error, and without having exact knowledge of how they were affecting the material