Comparison of gold leaf thickness in Namban folding screens using X-ray fluorescence

Abstract

In this work, the thickness of the gold leaf applied in six Japanese folding screens is compared using a nondestructive approach. Four screens belonging to the Momoyama period (*1573-1603) and two screens belonging to the early Edo period (*1603-1868) were analyzed in situ using energy dispersive X-ray fluorescence, and the thickness of the applied gold leaf was evaluated using a methodology based on the attenuation of the different characteristic lines of gold in the gold leaf layer. Considering that the leaf may well not be made of pure gold, we established that, for the purpose of comparing the intensity ratios of the Au lines, layers made with gold leaf of high grade can be considered identical. The gold leaf applied in one of the screens from the Edo period was found to be thinner than the gold leaf applied in the other ones. This is consistent with the development of the beating technology to obtain ever more thin gold leafs.

Determination of gold leaf thickness using X-ray fluorescence spectrometry: Accuracy comparison using analytical methodology and Monte Carlo simulations

“…This method relied on the comparison with the analysis of the substrate without coating, which is, sometimes, not possible. This was the case of the study and comparison of the gold leaf in a set on Namban folding screens, where only the different characteristic lines of Au were determined and compared in order to assess different thicknesses (Pessanha et al, 2014b). Buccolieri et al (Buccolieri et al, 2018) used the total attenuation of the radiation coming from an 241 Am γ-ray source for the determination of the thickness of a wreath of gold leaves from the National Archaeological Museum of Taranto, while Ferreti et al (Ferretti et al, 2013) derived the thickness of gilded silver using the mass fractions for Ag-K and Ag-K in the XRF spectra.…”

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

“…Portable instruments with unfiltered radiation can be used to obtain reliable results in the study of ancient and artistically important artifacts. [ 6 ]…”

“…The method that uses the differential attenuation of fluorescence radiation coming from the internal matrix (substrate) [ 31 ] is based on the concatenated effect of two distinct processes: (a) the production of fluorescence photons in the internal matrix, and (b) the differential attenuation in the surface layer. [ 6 ] These methods were designed to be implemented using a monochromatic X‐ray source. This is not the case in most circumstances, where only some kind of filtering is used to partially reduce the background or even no filtering and the direct bremsstrahlung from the tube is applied for analysis.…”

“…[ 4,5 ] The interaction of X‐rays with a sample with different layers leads to a clear change in the intensity ratio between the different characteristic lines, which can be used to determine the thickness of the different layers. [ 6,7 ] The ratio of the characteristic line intensities of an element in the substrate depends on, and can be also used to measure, the thickness of the coating. [ 8–14 ] A multivariate statistical method, the ordinary partial least squares (PLS) regression, was also used to obtain the thickness of the overlapping layer of objects coated with silver [ 7 ] and gold.…”

2015 Atomic Spectrometry Update – a review of advances in X-ray fluorescence spectrometry and their applications

“…The investigators used various techniques including XRF to demonstrate the coexistence of different levels of wear and colours of gold, the extensive use of hard soldering by the addition of Cu to gold-based alloys and the presence of PGE inclusions implying the use of alluvial gold or recycled alloys of alluvial gold. The thickness of gold leaf applied to six Japanese folding screens from the Momoyama (1573-1603 AD) and Edo (1603-1868 AD) periods was reported by Pessanha et al 330 The authors made measurements in situ by EDXRF instrumentation using a methodology based on the differential attenuation of different characteristic lines of Au in the gold leaf layer. Results indicated the use of fresh rather than recycled Cu-Sn binary alloys, with the relative concentrations adjusted according to use to be made of the alloy.…”