António Candeias

Extracting natural dyes from wool—an evaluation of extraction methods

The efficiency of eight different procedures used for the extraction of natural dyes was evaluated using contemporary wool samples dyed with cochineal, madder, woad, weld, brazilwood and logwood. Comparison was made based on the LC-DAD peak areas of the natural dye’s main components which had been extracted from the wool samples. Among the tested methods, an extraction procedure with Na2EDTA in water/DMF (1:1, v/v) proved to be the most suitable for the extraction of the studied dyes, which presented a wide range of chemical structures. The identification of the natural dyes used in the making of an eighteenth century Arraiolos carpet was possible using the Na2EDTA/DMF extraction of the wool embroidery samples and an LC-DAD-MS methodology. The effectiveness of the Na2EDTA/DMF extraction method was particularly observed in the extraction of weld dye components. Nine flavone derivatives previously identified in weld extracts could be identified in a single historical sample, confirming the use of this natural dye in the making of Arraiolos carpets. Indigo and brazilwood were also identified in the samples, and despite the fact that these natural dyes were referred in the historical recipes of Arraiolos dyeing, it is the first time that the use of brazilwood is confirmed. Mordant analysis by ICP-MS identified the widespread use of alum in the dyeing process, but in some samples with darker hues, high amounts of iron were found instead.

Cadmium accumulation and antioxidative defences in Brassica juncea L. Czern, Nicotiana tabacum L. and Solanum nigrum L.

Remediation of sites contaminated with heavy metals using hyperaccumulators seems a promising alternative to engineering approaches. In this work, we compared cadmium (Cd) accumulation and tolerance (based on responses to oxidative stress) in three different species, Brassica juncea (L.) Czern, Nicotiana tabacum L. and Solanum nigrum L., described in the literature as very tolerant or even as hyperaccumulators. The plants were grown in soil spiked with different Cd concentrations (0 – 35 mg kg−1) over a period of 90 days. The translocation factor (TF), used to measure the effectiveness to translocate Cd from roots to shoots, depended greatly on the species. N. tabacum was the plant which exhibited the highest TF values. It was the only plant under study that fulfilled the conditions of a hyperaccumulator for all levels of soil contamination. On the other hand, S. nigrum presented the highest Cd concentration in plant tissues, with TF >1 in the presence of 5 mg Cd kg−1 of soil. Although B. juncea had presented the lowest TF and Cd concentrations, it was the only plant with TF values increasing with the level of cadmium. Oxidative stress in plants was evaluated by lipid peroxidation and activities of catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (GPX) and superoxide dismutase (SOD), both in roots and shoots. A significant enhancement (versus control) on lipid peroxidation and enzymatic activity of CAT and APX in shoots of B. juncea, N. tabacum and S. nigrum was observed for the highest levels of Cd in soil, 15 and/or 35 mg Cd kg−1. B. juncea presented the most sensitive response of GPX, for all levels of Cd in soil. Lipid peroxidation and CAT activity were greater in shoots than in roots for all plants and soil Cd concentrations. SOD activity did not present consistent trends for any plant.

Microbial communities analysis assessed by pyrosequencing--a new approach applied to conservation state studies of mural paintings.

The knowledge about the microbial communities present in mural paintings is of utmost importance to develop effective conservation and mitigation strategies. The present paper describes a methodological approach for the detailed characterisation of microorganisms thriving in mural paintings by combining culture-dependent methods that allow the identification of microorganisms capable of growing in the laboratory conditions and to obtain high cell densities for further studies, and culture independent methods, such as denaturing gradient gel electrophoresis (DGGE) and pyrosequencing. The coupled use of culture-dependent methods and DGGE does not give enough information to investigate the diversity and abundance of microorganisms present in wall paintings. Pyrosequencing, a novel molecular technique, used here for the first time in this area of research, allowed the identification of a large number of microorganisms, confirming some already identified by the cultivation-dependent methods such as fungi of the genera Penicillium and Cladosporium, but also providing a great contribution in the identification of several genera and species, not previously identified in these artworks, giving also a detailed overview of contaminants which was not possible with the other approaches. The results obtained on several mural painting samples show a strong relationship between the most deteriorated areas of the paintings and higher microbial contamination.

Weathering of S. Domingos (Iberian Pyritic Belt) abandoned mine slags

Abstract The S. Domingos abandoned mine is a major source of pollutant-metals contamination. Slags from the 19th-20th century contain the most hazardous material. However, the release of pollutant metals depends on the metal-retention capability of weathering products. This work shows that Zn is not effectively retained by these weathering products while As and Pb are partially stored in sulphates. Copper, on the other hand, has a different behaviour and is the most leachable of the elements studied.

Material Characterization and Biodegradation Assessment of Mural Paintings: Renaissance Frescoes from Santo Aleixo Church, Southern Portugal

The aim of this work is the material characterization of wall paintings and biodegradation assessment, including the analysis of microbial growth and the effect of microbial proliferation, in view of their conservation. The methodology was applied to the study of frescoes dated from 1531, located in the ancient parish church of Santo Aleixo, Southern Portugal. The combined use of optical microscopy, scanning electron microscopy coupled with energy dispersive X-ray spectrometry (SEM-EDS) and μ- X-ray diffraction (XRD) showed that the painting palette is composed of red and yellow ochers, malachite, azurite, and bone black. The pigments do not show signs of chemical deterioration, except for malachite, which transformed to black copper oxide (tenorite). The microbiological study allowed the identification of several bacterial strains (e.g., Gram+ cocci, Gram+ bacilli, Actinomycetes sp.), yeast strains, and filamentous fungi of the genera Penicillium, Cladosporium and Aspergillus, among others of the microflora present in the paintings. Their metabolic activity is primarily responsible for the physical disruption of paint layers and underlying mortars. The combined approach using SEM analysis and enzymatic dehydrogenase measurement allowed the evaluation of microflora proliferation and diagnosis of the biodeterioration of the mural paintings. Additionally, the effect of some commercial biocides was evaluated for the predominant strains in order to select the most efficient biocide.

Blue Pigment Colors from Wall Painting Churches in Danger (Portugal 15th to 18th Century): Identification, Diagnosis, and Color Evaluation

Samples of blue wall paint layers from selected 15th to 18th century religious mural paintings from southern Portugal (Alentejo) have been analyzed using a multi-analytical methodology involving the combination of in situ visible spectro-colorimetry with microanalytical techniques such as optical and scanning electron microscopy and Raman spectroscopy. In situ analyses and micro-sampling were carried out in nine different churches, many in an advanced state of deterioration. The objectives of this study were: (a) to identify and compare the pigments that were used in the blue paint layers across the Alentejo region and through time by analysis of the elemental and mineralogical composition and pictorial techniques, and (b) to correlate the data between the actual color of the paint layer and the state of conservation of the pigments. For the paintings dated from the 16th century forward, the results show a generalized use of smalt blue. To a lesser extent, natural azurite was used despite the geological richness of the region in copper and pyrite ores. In only one painting was an optical blue made of carbon black and lime found. The pigments, pure or mixed with red and yellow ochres, were coarsely ground and used in different concentrations to create three-dimensional effects. These parameters as well as the presence of iron oxides in underlayer paints influence the colorimetric coordinates in the more transparent smalt blue paint layers. The state of conservation of the pigments plays an important role in the alteration of the paint color. A clear example of this is the fading of the smalt blue in several paintings due to lixiviation processes.

Characterisation of Roman Mortars from the Archaeological Site of Tróia (Portugal)

Roman mortars from the industrial archaeological site of Tróia (Portugal) have been studied by means of chemical, mineralogical and microstructural analysis. The mortars are calcitic aerial lime mortars differing in the type and proportion of aggregates used, including crushed carbonaceous rocks (limestone and dolomite), siliceous sand and crushed ceramics. The results show that although these mortars have been subjected to a very aggressive environment they are still in a very good state of conservation.

On the Use of the Unusual Green Pigment Brochantite (Cu 4 (SO 4 )(OH) 6 ) in the 16th-Century Portuguese- Flemish Paintings Attributed to The Master Frei Carlos Workshop

This paper reports an unusual green pigment, brochantite (Cu4(SO4)(OH)6), on 16th-century Portuguese-Flemish paintings, attributed to the Master Frei Carlos workshop. This green mineral is usually identified as an impurity or alteration product in the green pigments verdigris (Cu(CH3COO)2 nCu(OH)2) or malachite (CuCO3 Cu(OH)2). However, after thorough investigation with a broad range of analytical techniques, it became clear that, in this case, brochantite was applied as a pigment. The abundance, pigment granulometry, and pigment morphology suggest intentional use by this Portuguese-Flemish Master as a natural pigment rather than its accidental use as an alteration product. This seems to be a distinguishable feature to other painters (Flemish and Portuguese) working in Portugal at the beginning of the 16th century. The multi-analytical study of these easel paintings was first performed by physical imaging techniques and material characterization was carried out by optical microscopy, micro-Fourier-transform infrared-spectroscopy, micro-Raman spectroscopy, scanning electron microscopy coupled with energy dispersive X-ray spectrometry, and micro-X-ray diffraction analysis (XRD).

Study of mural paintings using in situ XRF, confocal synchrotron-μ-XRF, μ-XRD, optical microscopy, and SEM-EDS--the case of the frescoes from Misericordia Church of Odemira.

In this work, we present the results of an analytical method developed for detailed pigment identification, stratigraphy, and degradation of the paint layers of mural paintings applied in the study of the 17th century frescoes from the Misericordia Church of Odemira (Southwest Portugal). In situ X-ray fluorescence spectrometry analyses were performed on three panels of the mural paintings and complemented by colorimetric measurements. The different color areas were also sampled as microfragments (approx. 1 mm2) that were studied as taken or mounted in epoxy resin to expose the different paint layers. The microfragments of paint layers and their cross sections were characterized by optical microscopy and scanning electron microscopy coupled with energy dispersive X-ray spectrometry. Furthermore, elemental analysis was obtained with spatially resolved confocal synchrotron radiation μ-X-ray fluorescence spectrometry performed at ANKA synchrotron FLUO beamline. Occasionally, phase analysis by μ-X-ray diffraction was also performed. Results from the different techniques allowed pigment identification and, in some cases, the evaluation of color changes due to degradation processes and, considering the Southern Portugal geology, the identification of their possible provenance. The pigments used were essentially yellow, brown and red ochres, smalt blue, copper green, and black earths, probably from local sources.

Characterization of glue sizing under calcium carbonate ground layers in Flemish and Luso-Flemish painting – analysis by SEM-EDS, μ-XRD and μ-Raman spectroscopy

This work regards the study of painting techniques in Portuguese workshops of the 15th and early 16th centuries, specifically addressing the methodology used on the preparation of ground layers. The influence of Flemish painting in Portugal is evident in stylistic and iconographic themes of that period. As regards the painting materials, we confirmed that this influence also extended to the ground layer technique. The use of a sizing layer with calcium sulphate or garlic to isolate the support from the calcium carbonate layer was verified by SEM-EDS but not confirmed by μ-XRD or μ-Raman spectroscopy. This work is part of a larger project, “The invisible ground layer and its influence in Portuguese paintings from the 15th and 16th centuries: a question to be settled”.