Mapping Henry: Dendrochronological Analysis of a Sixteenth-Century Panel Painting Based Upon Synchrotron-Sourced X-ray Fluorescence Mapping

Abstract

The study of materials that comprise artworks significantly contributes to understanding of age and provenance. While dendrochronology is a particularly valuable and well-established technique for panel paintings comprising oak timber, conventional practices of resurfacing endgrains to reveal tree rings is becoming less acceptable because it removes material, modifying the painting. Recently, application of non-destructive X-ray fluorescence (XRF) spectroscopy to a portrait of Henry VIII held by the Art Gallery of NSW (AGNSW) revealed tree-ring boundaries in the resulting high-resolution elastic scatter XRF map. In this study, we examine the dendrochronological potential of that mapping with the aim of contributing to resolving the relation of the AGNSW portrait to similar paintings elsewhere. Examination of the timber revealed affinities with Quercus petraea (Matt.). We measured tree-ring widths along multiple paths in the XRF scatter map and crossdated the resulting 81-year XRF ring-width (XRF portrait ) series against master chronologies of English, western European, and Baltic origin. Rather than an arbitrarily defined threshold, we used a Bonferroni correction to determine a minimum significance level for crossdating. While the XRF portrait series did not crossdate with the continental European chronologies, we identified a single significant (α = 3.4 x 10 -6 ) dating position with the English chronology (1400-1480 CE). Cross-matching with site-level chronologies revealed a cluster of high t-values in central-southern England. The earliest date of felling precedes the documented date of completion for the AGNSW and two similar Tudor portraits of Henry VIII held by the National Portrait Gallery (NPG), London and one at the Society of Antiquaries, London. While, the apparent British provenance of timber used in the AGNSW portrait contrasts to Baltic origin of timbers used for the two NPG portraits and the majority of English panel paintings, it is consistent with the provenance of the timber used for the Society of Antiquaries portrait.

X-ray computed tomography for non-invasive dendrochronology reveals a concealed double panelling on a painting from Rubens’ studio

“…The optimal scanning routine may be different for other panels, as the paint material, the length of the panel, the size of the detector, the focal spot size of the tube and the space constraints of the X-ray facility are factors that influence the range of motion and reconstructed image quality. Further, monochromatic X-ray beams or polychromatic X-ray beams with higher photon count (higher tube voltage and power settings) such as those available at synchrotrons could result in less noisy X-ray images with reduced imaging artefacts [64,65].…”

Using machine learning on tree‐ring data to determine the geographical provenance of historical construction timbers

“…These samples are often collected from local historical construction wood of unknown origin (Büntgen et al, 2005; Hartl et al, 2022; Klippel et al, 2020; Labuhn et al, 2016; Liu et al, 2009; Schweingruber, 1988; Tegel et al, 2010; Wilson et al, 2005). The determination of the origin of ancient wood, the so‐called dendroprovenancing, is a frequently applied tool to reconstruct trade and transportation routes (Bonde et al, 1997; Daly & Tyers, 2022; Linderholm et al, 2021; Shindo & Claude, 2019; Wazny, 2002), to uncover illegal logging (Kagawa & Leavitt, 2010), and determine the origin of artwork or shipwrecks (Bridge, 2011; Brookhouse et al, 2021; Domínguez‐Delmás et al, 2020; Haneca et al, 2005). Classic approaches in dendroclimatology and ‐archaeology consider the correlation of series from unknown origin to a set of existing reference tree‐ring chronologies (Bonde, 1992; Bridge, 2012).…”