Study on Brazilian 18th century imperial carriage using x-ray nondestructive techniques

Nardes, Raysa C.; Silva, Marcelo Souza da; Rezier, A.N.S.; Sanches, F.A.C.R.A.; Filho, Hamilton S. Gama; Santos, Ramon Silva dos; Oliveira, Davi F.; Lopes, Ricardo Tadeu; Carvalho, Luísa; Cesáreo, R.; Zanatta, E.M.; Assis, Joaquim T. de; Anjos, M.J.

doi:10.1016/j.radphyschem.2018.04.005

Cited by 14 publications

(7 citation statements)

References 12 publications

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“…This value can also be experimentally determined by directly measuring the sample exposed substrate or by creating a calibration model via Monte Carlo simulations (Pessanha et al, 2019a) when the former is not feasible. Therefore, assuming the attenuation coefficient of the overlapping layer is known (its composition is known or experimentally determined using the acquired XRF data) and that the matrix can be considered infinitely thick, the superficial layer thickness is finally given by Equation ( 5) below (Cesareo et al, 2016;Nardes et al, 2019):…”

Section: The Differential Attenuation Methodsmentioning

confidence: 99%

“…The existence of an "extra" layer on top of the gilding layer further attenuates the photons coming from the substrate and therefore introduce systematic errors. If the protective layer is known, as in the case of paraloids, the further attenuation introduced can be calculated and Equation (5) can be adjusted accordingly (Nardes et al, 2019). Past interventions or cleaning routines applied to the objects surface can be assessed by the complete absence of soil impurities in the elemental distribution maps generated with the MA-XRF data.…”

Section: Introductionmentioning

confidence: 99%

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Differential X-Ray Attenuation in MA-XRF Analysis for a Non-invasive Determination of Gilding Thickness

et al. 2020

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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.

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Section: The Differential Attenuation Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Differential X-Ray Attenuation in MA-XRF Analysis for a Non-invasive Determination of Gilding Thickness

et al. 2020

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“…When measuring the substrate with resin (AoI A) the mean value was slightly lower: 5.20. The gold leaf thickness at each point was calculated following Equation (1) [9,18]:…”

Section: Differential Attenuationmentioning

confidence: 99%

“…An alternative to microsampling is the use of the differential attenuation of fluorescence radiation [8], basing on the concatenation effects of (a) the production of photons in the sample's substrate and (b) their subsequent attenuation by the gilding's uppermost layer. This approach has been previously applied to a series of objects of cultural heritage [9][10][11][12]. Nevertheless, archaeological materials and works of art are known to be considerably heterogeneous, i.e., the substrate underneath the gold foil can differ throughout the sample, so the study of only one or few points on the surface may yield biased information [8,13].…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, different mordants used to adhere the gold foils or leaves to the substrate surface and protective layers further applied to the finished gilded surface can enhance the attenuation effects. Nardes et al [9], when investigating gold foils protected with mica, demonstrated that the addition of a protective layer can introduce considerable errors to the estimated mean thickness by the different attenuation method.…”

Section: Introductionmentioning

confidence: 99%

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Testing the Accuracy of the Calculation of Gold Leaf Thickness by MC Simulations and MA-XRF Scanning

et al. 2020

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The use of X-ray fluorescence (XRF) scanning systems has become a common practice in many application sectors. In multistratified and heterogeneous samples, the simple analysis of an XRF spectrum as a response of the entire sample is not reliable, so different spectral analysis techniques have been proposed to detect the presence of surface stratification. One commonly studied case is that of gilding, i.e., the presence of a superimposing gold-leaf layer. The observation of changes in the net peak ratios of a single element or of several elements in an XRF spectrum is a well-developed practice, but is still not used in the case of XRF scanning (macro-X-Ray fluorescence scanning, MA-XRF), a technique that can be described as the extrapolation of XRF spot analysis to a second dimension, scanning a sample surface instead. This practice can yield information on the overlaying layer thickness, if some properties of the sample are known—or estimated—beforehand, e.g., the overlapping layer’s chemical composition and the matrix effect contribution from the bulk material (thick ratio). This work proposes the use of an algorithm to calculate the thickness distribution of a superimposing gold layer accurately and automatically through the differential attenuation method by using MA-XRF datasets in a total noninvasive manner. This approach has the clear advantage over the traditional spot sampling of allowing the generation of a surface heightmap to better visualize and interpret the data, as well as a considerably larger sample space. Monte Carlo simulations were used to verify the influence of the medium used to adhere the gold leaves to the substrate and to generate known spectra to assess the algorithm’s accuracy.

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Gold‐coating thickness determination on Ag, Cu, Fe, and Pb using a handheld X‐ray instrument

2021

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Here, the X‐ray fluorescence technique is used to determine the thickness of a coating layer as well as to analyze the surface of objects. Four metals (Ag, Cu, Fe, Pb) were covered with increasing thicknesses of gold. The measurements were performed with a commercial handheld instrument, X‐SORT (Spectro). In double layers, the thickness of the covering layer was assessed by (a) the ratio between the most intense fluorescence lines of the covered element, (b) a cross‐ratio between two lines of the elements in the two layers, and (c) the ordinary partial least squares (PLS) regression method. In all cases, the curves obtained could be used for the quantitative determination of the thickness. The experimental data followed the theoretical trend even though the values of the attenuation parameters were not always in agreement with the theoretical ones. Comparisons and discussion of the results of the different approaches and also with models in the literature are made. The methods studied were applied to determine the nature of the coating layers of some gilded objects and proved to be suitable for estimating the thickness of gold by providing results that were in good agreement with each other.

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Study on Brazilian 18th century imperial carriage using x-ray nondestructive techniques

Cited by 14 publications

References 12 publications

Differential X-Ray Attenuation in MA-XRF Analysis for a Non-invasive Determination of Gilding Thickness

Differential X-Ray Attenuation in MA-XRF Analysis for a Non-invasive Determination of Gilding Thickness

Testing the Accuracy of the Calculation of Gold Leaf Thickness by MC Simulations and MA-XRF Scanning

Gold‐coating thickness determination on Ag, Cu, Fe, and Pb using a handheld X‐ray instrument

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