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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.

The aim of this work is to compare the performance of two x‐ray fluorescence (XRF) spectrometers, a portable one and a non‐portable one, in order to evaluate the advantages and drawbacks of each system. The used spectrometers are not commercial, and in both cases the excitation beams are produced by x‐ray tubes and the detection systems are based on common detectors. The portable system is a 90° geometry between the incident and the emitted beams, and the stationary spectrometer is based on a triaxial geometry with a secondary target. Detection limits are compared for a metallic Cu alloy reference material. A case study for ancient metallic artefacts of Cu‐based alloys, is used to compare the performance of both spectrometers. With the portable spectrometer several tests were carried out using two modes: an ‘unfiltered’ and a ‘filtered’ one in order to evaluate the best peak/background ratio for the studied samples. The obtained results showed significant differences between the two systems, namely, in what concerns peak shaping and trace elements detection. Copyright © 2008 John Wiley & Sons, Ltd.

This work shows the first analytical results obtained by X-Ray Fluorescence (XRF) (conventional and 3D) and Scanning Electron Microscopy with Energy Dispersive System (SEM-EDS) on original Portuguese ceramic pieces produced between the 16 th and 18 th centuries in Coimbra and Lisbon. Experts distinguished these productions only based on the color, texture and brightness, which originates mislabeling in some cases.Thanks to lateral and spatial resolution in the micrometer regime, the results obtained with µ-XRF were essential in determining the glaze and pigment thicknesses by monitoring the profile of the most abundant element in each "layer". Furthermore, the dissemination of these elements throughout the glaze is different depending on the glaze composition, firing temperature and on the pigment itself. Hence, the crucial point of this investigation was to analyze and understand the interfaces color/glaze and glaze/ceramic support.Together with the XRF results, images captured by SEM and the corresponding semiquantitative EDS data revealed different manufacturing processes used by the two production centers. Different capture modes were suitable to distinguish different crystals from the minerals that confer the color of the pigments used and to enhance the fact that some of them are very well spread through the glassy matrix, sustaining the theory of an evolved and careful procedure in the manufacturing process of the glaze.

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