Differential X-ray attenuation in MA-XRF analysis for a non-invasive determination of gilding thickness

When investigating gilded artifacts or works of art, the determination of the gilding thickness plays a significant role in establishing restoration protocols or conservation strategies. Unfortunately, this is done by cross-sectioning the object, a destructive approach not always feasible. A non-destructive alternative, based on the differential attenuation of fluorescence radiation from the sample, has been developed in the past years, but due to the intrinsic random nature of X-rays, the study of single or few spots of an objects surface may yield biased information. Furthermore, considering the effects of both porosity and sample inhomogeneities is a practice commonly overlooked, which may introduce systematic errors. In order to overcome these matters, here we propose the extrapolation of the differential-attenuation method from single-spot X-ray fluorescence (XRF) measurements to macro-XRF (MA-XRF) scanning. In this work, an innovative algorithm was developed for evaluating the large amount of data coming from MA-XRF datasets and evaluate the thickness of a given overlapping layer over an area. This approach was adopted to study a gilded copper-based buckle from the sixteenth to seventeenth century found in Rome. The gilded object under investigation was also studied by other analytical techniques including scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS). Previous results obtained from SEM-EDS were used to confront the data obtained with the proposed methodology and validate it. MA-XRF elemental distribution maps were fundamental in identifying and choosing sampling areas to calculate the thickness of the gilding layer, avoiding lead islands present in the sample that could negatively influence the results. Albeit the large relative standard deviation, the mean thickness values fell within those found in literature and those obtained from previous studies with SEM-EDS. Surface fissure has been found to deeply affect the results obtained, an aspect that is often disregarded

A visão do envelhecimento, da velhice e do idoso veiculada por livros infanto-juvenis

Este estudo, de abordagem qualitativa e tipo descritivo-exploratório, analisa a visão do envelhecimento veiculada por livros infanto-juvenis. O caminho metodológico foi permeado pela seleção, aquisição e análise, utilizando-se a técnica de análise de conteúdo categorial por temática, de livros nacionais recomendados pelo Programa Nacional Biblioteca da Escola (PNBE), publicados entre 2003 e 2012, tendo em seu enredo a menção ao idoso e/ou à velhice e/ou ao envelhecimento de seres humanos. Identificaram-se duas grandes categorias temáticas, compostas por subcategorias: 1) aspectos biológicos na velhice, com as subcategorias senescência versus senilidade e mitos relacionados aos aspectos físicos dos idosos; e 2) aspectos psicossociais na velhice, com as subcategorias conhecimento e experiência de vida do idoso, intergeracionalidade, autorrealização na velhice, isolamento social, mitos relacionados à velhice e morte na velhice. Os resultados procuram contribuir para uma melhor utilização dos livros infanto-juvenis no processo educativo a respeito do tema envelhecimento, não só em termos de cidadania e civilidade como também em termos de educação em saúde

Thin thickness gilding determined by x-rays ratios from EDXRF-spectra

A by-product of energy-dispersive X-ray fluorescence (EDXRF)-analysis consists of using the ratios of selected X-ray peaks to determine the thickness of multilayered objects. Three different methods were developed in the past, all because the two main K or L X-lines from an EDXRF spectrum emitted by a chemical element have a distinct energy and are differently attenuated by an overlying layer. This specific subject has many papers dedicated, but only a few considerations were devoted to the limits of these methods, that is, the range, for example, of gold thickness that can be usefully determined by each method. This paper defines these limits in the specific case of thin gilding (with d < 1 μm). Three typical situations were considered, and the following artefacts were studied: two artefacts on gilded lead, where the gold leaf is superimposed to a white lead pigment, both in the painting “La Fornarina” of Raphael, dated 1520 AD, and in the imperial carriage of Dom Pedro II emperor of Brazil. In this last case, the white lead pigment was painted over the wood structure of the carriage; four artefacts on gilded copper, three crowns and a pendant, from the tomb of the Lady of Cao, from the Moche civilization of the North of Peru, dated around 350 AD; finally, an artefact on gilded silver, a vase from the Chavín civilization of the North of Peru, dated around 1000-200 BC

Modular MA-XRF scanner potentialities and further advances

In Heritage Science applications, in-situ and non-destructive analyses are commonly preferred. The valuable nature of historical objects often hinders the possibility of either sample or transport them into laboratories. Macro X-ray fluorescence (MA-XRF) has become widespread in the archaeometry field, due to its non-destructive and non-invasive characteristics and especially to the amount of information provided by the technique. Unfortunately, most of the instruments are either fixed or mobile, hindering their in-situ applications. Moreover, most of the mobile instrumentation are bulky and require some logistics for transportation. In this scope, a modular instrument has been developed. The scanner, which requires no more than one person to transport and assemble, has been tested and compared under compatible circumstances to state-of-the-art instrumentation. Preliminary results are presented and discussed