[show abstract][hide abstract] ABSTRACT: 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.
[show abstract][hide abstract] ABSTRACT: Wool samples were dyed with madder and alum, copper, and iron salts at different concentration by pre-mordanting (MD) and simultaneous mordanting (M + D) procedures. Samples were artificially aged to identify the influence of the mordant on the madder chromophores photodegradation. A set of analytical techniques was used for complete characterisation of the dyed fibres before and after light exposure, which included colour and chromophore analysis (colourimetry and LC-ESI-MS/MS analysis), determination of mordant ions amounts in the fibres (FAAS and ICP-OES analysis), morphological characterisation of the fibres and punctual chemical analysis (SEM-EDS studies).Fibre colour hue was found to be dependent on the mordant ion nature, mordant bath concentration and dyeing procedure. Mordant ion quantification showed that the uptake of metal ion by the fibres is relatively small, with the Cu ion presenting the highest affinity for the fibre. MD method yields fibres with higher amounts of metal ions and larger chromophore chromatographic peak areas corresponding, in general, to stronger colour hues. Photodegradation was more severe in alum mordant samples and in the first 480 h of light exposure. Chromophore degradation rates are unequal and dependent on the mordant nature, contributing for colour changes observed after light exposure.
[show abstract][hide abstract] ABSTRACT: The trees of the species Rhus vernicifera, Rhus succedanea and Melanorrhoea usitate grow in various regions of Asia and their sap is used, for thousands of years, as coating materials for the most varied kinds of objects. After drying, the sap of these trees forms a very hard and durable polymer, commonly known as oriental lacquer. The sap consists of water, polysaccharides, glycoproteins, enzymes and a mixture of derivatives of catechol whose composition differs with the species. In this work, pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) was applied successfully to the identification of these species through the analysis of their saps. The saps of the three species of lacquer trees were studied and the method developed was applied to identify a tree whose species was unknown. Results show that pyrolysis is an alternative and efficient technique to identify the species of lacquer trees.
Journal of Analytical and Applied Pyrolysis. 01/2010; 89(1):117-121.
[show abstract][hide abstract] ABSTRACT: The reddish-brown, brown or yellowish stains of circular or irregular shape known as foxing spots have been fully described in conservation literature but still, this phenomenon does not find any scientific agreement since many hypotheses have been raised concerning their origin. In this work a contribution to foxing definition not only focussed on its appearance but also reported on its chemical information. For this purpose foxing stains present in drawings from two Portuguese artists dated from the eighteenth to nineteenth centuries were observed under ultra-violet light and optical microscope and analysed by three non-invasive spectroscopy techniques. The observations carried out on the stains provided information on their surface morphology. The use of energy-dispersive X-ray fluorescence revealed a variation on the elemental content between foxing and paper region. Although the results from X-ray diffraction analysis showed no signs of cellulose degradation in foxing stains, Fourier-transformed infrared analysis revealed the presence of oxide groups. Both the information on the chemical nature and surface morphology of the stains achieved in this study will contribute to increase foxing formation information and develop future protocols for conservation purposes.
Analytical and Bioanalytical Chemistry 09/2009; 395(7):2029-36. · 3.66 Impact Factor
[show abstract][hide abstract] ABSTRACT: Arraiolos tapestries are probably one of the richest artistic Portuguese expressions in terms of textile heritage. It is difficult to date the beginning of the production of rugs in Arraiolos (Southern Portugal), but they were already produced in the late 1600's as they are listed in the inventories of Portuguese aristocratic households in the beginning of the 18th century. Sensitive detection techniques play an increasing role in the chemical investigation of historical objects since the knowledge derived from the chemical composition of materials is of upmost importance for textile conservation and restoration purposes. Textiles deteriorate due to natural causes like heat, radiation, mechanical stress, moisture, microbiological and enzymatic attack. Deterioration of materials causes breakdown of the molecular structure and results in a loss of strength, extensibility and durability, discoloration and fading which affects the appearance of the textiles.
[show abstract][hide abstract] ABSTRACT: Pigments used in traditional limewashing paintings in Alentejo urban Heritage are inorganic materials and can be grouped into
four categories: a) reds – red ochre (from terras rossas, red schists and iron ore deposits weathering), almagres, terra roxa
(natural processed red ochres) and synthetic red iron oxides; b) yellows – yellow ochre (from schists and iron ore deposits),
processed natural ochres, yellow iron synthetic oxides, c) blacks – black earths and black iron synthetic oxides and d) blues
– artificial ultramarine. The present work proposes to characterize natural, natural processed and synthetic pigments by comparing
phase and elemental compositions. The results reveal differences in Fe, Si, K and Al total content according to their origin
and fabrication process and reveal intentional addition of white charges like carbonates. Elements like Zr, Ti, Cr, Mn, Ca
and Zn are present in all categories. Under optical microscopy, some samples of processed natural pigments do not exhibit
optical activity, thus revealing mixtures with synthetic pigments, while natural pigments present a strong birefringence colorless
due to optically active minerals.
Applied Physics A 12/2007; 90(1):49-54. · 1.55 Impact Factor