Caracterización química y mineralógica de cerámicas del bronce final en el Ribatejo Norte ( Centro de Portugal):primeros resultados de Quinta Da Pedreira (Abrantes)

El yacimiento de Quinta da Pedreira (Abrantes), ubicado en una terraza pleistocénica en la orilla derecha del Tajo, viene estudiándose sistemáticamente desde 1994, en el marco de un proyecto de investigación que busca la construcción de un modelo explicativo del proceso histórico observado en el Ribatejo Norte en la transición Bronce-Hierro (1200-700 a.C.). Entre el conjunto de fragmentos de cerámica doméstica recogidos en este yacimiento, se ha seleccionado una mues tra compuesta por 15 fragmentos de piezas distintas, procediéndose a su carac terización química (FRX), mineralógica (DRX) y textural (MOLT). Los resulta dos obtenidos han sido manejados bajo procedimientos estadísticos multivariantes, en especial análisis de componentes principales y análisis cluster

Calcium sulfate fillers and binders in Portuguese 15th and 16th centuries: Ground layers from a family painting workshop — Study by multianalytical spectroscopic techniques

This study presents results on a developed methodology to characterize ground layers in Portuguese workshops. In this work a set of altarpieces of the 15th and 16th centuries, assigned to Coimbra painting workshop was studied, overall the masters Vicente Gil (doc. Coimbra 1498–1525), Manuel Vicente (doc. Coimbra 1521–1530) and Bernardo Manuel (act. c. 1559–94), father, son and grandson, encompassing from late gothic to mannerist periods. The aim of the study is to compare ground layers, fillers and binders of Coimbra workshop, and to correlate their characteristics to understand the technical evolution of this family of painters, using complementary microscopic techniques. The cross-sections from the groups of paintings were examined by optical microscopy and the results were integrated through the analysis obtained by μ-X–ray diffraction, scanning electron microscopy with energy dispersive X–ray Spectrometry, μ-confocal Raman and occasionally with μ-Fourier transform infrared spectroscopy imaging. Ground layers are of calcium sulfate, present as gesso grosso (mainly anhydrite with small amounts of gypsum) in the first and last phases of the workshop and gesso mate (mainly gypsum with small amounts of anhydrite) in an intermediate period. Binders have protein and oleic characteristics

Technical replicas of Portuguese ceramic tile bodies produced in the Oporto region in the late nineteenth to early twentieth centuries

Portugal is well known for its facades decorated entirely with ornamented glazed ceramic wall tiles called azulejos. On ageing, the tiles may detach and fall off, or deteriorate to such an extent that it becomes necessary to replicate them. Hence tile replication is a common practice in Portugal for facade restoration, but very often these new tiles do not have the same physical and/or chemical properties as the original ones. Such differences might be a factor in differential deterioration of the facades after restoration. One step toward an improvement in compatibility is to make new ceramic bodies with the same characteristics as the original ones. This study focuses on two types of glazed ceramic wall tiles from the Oporto region in Portugal: 'calcic faience' and po de pedra. A total of 25 samples from the late nineteenth to early twentieth centuries were studied systematically as an attempt to improve knowledge of these materials and to create a basis for their replication. All samples were collected from facades that were under conservation/restoration at the time when sampling was performed. The original traditional ceramic bodies were analyzed by X-ray diffraction and X-ray fluorescence. Total open porosity, capillary absorption coefficient, and mercury intrusion porosimetry were also measured in order to gain knowledge on their physical characteristics in addition to their chemical and mineralogical compositions. High-temperature crystalline phases such as diopside, gehlenite, and mullite were found in the calcic faience, suggesting that the firing temperature of calcic faience bodies was within the range of 1100-1150 degrees C. Calcination trials were also performed in order to determine the most probable firing temperatures of the ceramic bodies. Collected data led to the assumption that the raw materials used for the ceramic bodies were kaolinitic clay, quartz sand, limestone, and talc. The raw materials for po de pedra tiles were found to include kaolinite clay and quartz with firing temperatures estimated within the temperature range of 1150-1360 degrees C. Technical replicas made on the basis of these investigations were found to have the same mineralogical and capillary properties as the original tiles