Art, Conservation and Restoration

In the brewing process, kieselguhr performs as a filtration medium and one generated by-product is a sludge containing kieselguhr, which is mainly composed of fragmented diatom frustules associated to organic material retained during the clarification process.The physic-mechanic tests were performed on assemblages with brick composition and brewing spent kieselguhr containing 3, 9, and 15 wt% incorporation levels of sludge, being extruded and dried (105°C) before being submitted to slow firing at 900°C, 950°C, and 1000°C.The obtained results showed that, even when at its maximum incorporation level, the spent kieselguhr for all firing temperatures do not cause important losses on the properties exhibited by the clay paste without kieselguhr incorporation and the best incorporation levels are 4.2 wt% when fired at 900°C, 9.8 wt% when fired at 950°C, and 13.4 wt% when fired at 1000°C. When fired at 950°C, 15 wt% addition of spent kieselguhr increased by 27% the open porosity and decreased by 10% the bulk density of the brick paste.Furthermore, physic-mechanic tests and ecotoxicity evaluation on semi-industrial brick manufactured with 9 wt% of brewing spent kieselguhr were accessed. The results do no show any constrain concerning mechanical properties, and the ecotoxicity evaluation shows the safety of the brewing spent kieselguhr incorporation in ceramic products.

Abstract Several mortars from mural paintings were collected from the Misericórdia Church of Odemira and analysed by using different techniques namely X-ray diffraction, thermogravimetric analysis with differential thermal analysis, SEM-EDX, optical ...

The influence of carbonates in the temperature of Br volatilization during firing of clays and its implications in archaeometric studies are investigated. The main goal is to determine the circumstances in which Br content of fired products (“pottery”) can be considered inherited from raw material or added to ceramic pastes after production. Seven samples representing different types of clays (non-calcareous clays, calcite-rich clays and dolomite-rich clays) from Algarve region (South Portugal) were studied before and after firing at temperatures ranging from 300 °C to 1100 °C by steps of 100 °C. Original clays were characterized by major element geochemistry, obtained by X-ray fluorescence, and by mineralogy of bulk rock and < 2 μm fraction, using X-ray diffraction. The chemical composition of the test pieces (unfired and fired at various temperatures) of each clay was determined by instrumental neutron activation analysis, as it enables obtaining Br concentration with high precision and accuracy. Thermogravimetric analysis was done to better characterize mass changes after firing. The results confirm the influence of clays composition, especially the presence of carbonates rather than the clay minerals associations, on temperature of Br volatilization: i) in non-calcareous clays Br volatilized more intensely up to 600 °C, suggesting its association with combustion of organic matter and dehydroxylation of clay minerals; ii) in calcareous clays Br volatilized more strongly after 800―900 °C, suggesting that at least part of the process is associated with decarbonation reactions. As a result, this study contributes to elucidate that not all Br existing in pottery can be interpreted as a contamination product. Instead, Br can be inherited from raw material and its presence in pottery, particularly in carbonate-rich pastes, may simply indicate that the temperature attained in the kiln was not enough for its complete volatilization. Extending the Algarve study to other clay materials used in ancient ceramics, the conclusions of this study may assist broad archaeometric studies.►Influence of clays composition on temperature of bromine volatilization. ►In calcareous clays Br volatilize at higher T associated to decarbonation reaction. ►Bromine in pottery can be added after production or inherited from raw material. ►Br in calcareous pastes may indicate T was not high enough to its volatilization.

The need for the formulation of mortars for repair of ancient Roman renders in the archaeological site of Conímbriga brought about the need for a study of the rendering solutions existent therein. Various samples were extracted and analysed by means of acid attack followed by determination of particle size distribution, execution and visualization of thin sections, thermal analysis and mineralogical and chemical analysis using XRD and XRF. This paper presents the results of four of the Conímbriga mortars; the results show similarities in terms of the raw materials that were used and crushed ceramic particle size.

Mineralogical transformations during firing of two extremely calcareous clays, one calcite and other dolomite rich, and relatively poor in silica were studied. Original clays were mineralogical and chemically characterized with X-ray diffraction (XRD) and X-ray fluorescence (XRF). Firing of both clays was carried out in the temperature range 300–1100 °C under oxidizing conditions and the mineralogical transformations were investigated with XRD, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and scanning electron microscopy associated with energy dispersive X-ray spectroscopy (SEM-EDS).Important compositional differences in the neoformed phases were observed between calcite and dolomite rich clays. In the Ca-rich clay the assemblage gehlenite + wollastonite + larnite was observed. In the Mg(Ca)-rich clay the reaction products included akermanite, diopside, monticellite, forsterite, periclase and spinel.XRD and SEM-EDS showed the presence, in both clays, of a potassium–calcium sulfate in samples fired between 900 and 1100 °C.

According to treatises on 15th and 16th century paintings, artists dedicated particular attention to the sizing layer—consisting mainly of animal glue applied onto the wood support before further application of the ground layer. The stability of a painting mainly depends on the presence of a very cohesive sizing layer. However, the study of these layers has not received special attention from researchers. In this article we present a methodology for characterization of the sizing layer both chemically, by IR spectroscopy (Fourier transform infrared spectroscopy), and morphologically, by scanning electron microscopy (SEM). Secondary electron images obtained by SEM allow precise characterization of such layers. Painting reconstructions were used as references in development of the method to study the sizing layer in real painting samples. Presented herein are examples of this study on 15th and 16th century Portuguese paintings, particularly on the Triptych of S. Simão, from the Aveiro Museum, and S. Pedro, belonging to the Mercy of Tavira.(Received June 07 2013)(Accepted September 10 2013)

... The semi-quantitative results were based on a peak-to-background ZAF evaluation method (P/B-ZAF), ZAF representing a matrix correction, mainly based on analytical expressions for atomic number (Z), dependent X-ray yield, self-absorption (A), and secondary fluorescence ...

ABSTRACT No concelho de Tarouca situam-se dos mais significativos monumentos portugueses, com um representativo espólio de pintura portuguesa dos séculos XV e XVI. Entre os vários espécimes encontra-se o da igreja de São Pedro de Tarouca, que integra uma pintura mural, com o tema da “Ressurreição”, situada no arcossólio da nave da Igreja. Trata-se de uma pintura que se destaca pela sua singularidade, existindo poucos exemplares desta época nesta região do país. A pintura, pela sua raridade, foi objecto de estudo e análise laboratorial aquando da intervenção de conservação e restauro, que deixou a descoberto uma obra de carácter marcadamente maneirista, que se encontrava totalmente repintada. Neste sentido, discute-se o contexto cronológico e estilístico da obra, apresenta-se o estudo dos pigmentos utilizados e descreve-se a metodologia de intervenção adoptada, dando a conhecer os aspectos mais relevantes da sua análise, tais como a presença do pigmento amarelo de Nápoles ou as alterações observadas na iconografia da pintura após a intervenção.