Scanning X-ray Fluorescence Data Analysis for the Identification of Byzantine Icons' Materials, Techniques, and State of Preservation: A Case Study.

X-ray fluorescence (XRF) spectrometry has proven to be a core, non-destructive, analytical technique in cultural heritage studies mainly because of its non-invasive character and ability to rapidly reveal the elemental composition of the analyzed artifacts. Being able to penetrate deeper into matter than the visible light, X-rays allow further analysis that may eventually lead to the extraction of information that pertains to the substrate(s) of an artifact. The recently developed scanning macroscopic X-ray fluorescence method (MA-XRF) allows for the extraction of elemental distribution images. The present work aimed at comparing two different analysis methods for interpreting the large number of XRF spectra collected in the framework of MA-XRF analysis. The measured spectra were analyzed in two ways: a merely spectroscopic approach and an exploratory data analysis approach. The potentialities of the applied methods are showcased on a notable 18th-century Greek religious panel painting. The spectroscopic approach separately analyses each one of the measured spectra and leads to the construction of single-element spatial distribution images (element maps). The statistical data analysis approach leads to the grouping of all spectra into distinct clusters with common features, while afterward dimensionality reduction algorithms help reduce thousands of channels of XRF spectra in an easily perceived dataset of two-dimensional images. The two analytical approaches allow extracting detailed information about the pigments used and paint layer stratigraphy (i.e., painting technique) as well as restoration interventions/state of preservation.

Kynos Through Time: Decorated Pottery Sherds from Eleven Strata of a Homeric Greek Site.

Excavations at the Kynos settlement, a Homeric site and the home of an early school of key Greek pictorial pottery painting, revealed extensive remains of several chronological horizons which continuously span the period from Middle Helladic (∼2100 BC) to Byzantine times (330 AD onwards), along with thousands of decorated sherds. The scope of the present study is the exploration of the technological traits of this pottery, which would contribute substantially to the archaeological understanding of the site. Samples from a sizeable assembly of decorated sherds were studied by means of analytical techniques, i.e., scanning electron microscopy-energy dispersive X-ray (SEM-EDX) analyzer, micro X-ray fluorescence (µXRF), and portable X-ray fluorescence (pXRF). Results indicate that the dark decorations have been achieved by versions of the iron reduction (IRe) technique using mostly materials identical to those of the red decorations, while for the white decorations contrast-enhancing Ca-Mg-enriched clays were used. All coexisting red and dark hues reflect similar compositions while the color difference is due to the thicker application of the darker decorations, which are thus not affected by the last oxidative firing stage of the IRe technique. X-ray fluorescence analysis focusing on several clay-origin markers shows that only a minority of samples is of non-local character and continuity in Kynos pottery tradition, at least as far as raw materials is suggested. Some of the local body-clays exhibit a puzzling enhanced level of Ni, Cu, and Zn at a nearly fixed ratio. Finally, we find that XRF may provide valuable nondestructive analysis in the case of fine pottery decorative layers of cultural significance.