The representation of skin colour in medieval stained glasses: The role of manganese

The present study concerns a corpus of 17 glass pieces representing character heads, originating from 11 major cathedrals and churches North Western France which constitute the masterpiece stained windows. Skin complexion ranges colourless to flesh-tone purple. These glasses have been investigated using non-destructive non-invasive techniques. Particle Induced X-ray Emission Gamma analyses at AGLAE show that these potassic plant ash compositions, typical 12th −15th centuries. compositional variability components remains limited, similar found for single monuments, despite diversity geographic origins. Mn Ba concentrations follow different trend in flesh-coloured or purple glasses, suggesting sources two kinds originated raw materials. Purple flesh tone contain more manganese than with an almost iron content. Synchrotron absorption near-edge structure spectroscopy (XANES) portable UV–visible-NIR optical indicate colour varies results Fe2+, Fe3+, Mn2+ Mn3+. thickness about 3 mm, has measured ultrasound Its dispersion is various coloured glasses. This parameter mostly influences saturation but not hue. Obtaining requires some control oxidation state during making. Divalent largely prevalent change hues driven by small variations Mn3+ As are related Fe/Mn ratio, resulting difficult predict on only basis composition. Due low kinetics obtaining redox equilibrium between furnace atmosphere silicate melt, Mn4+- Mn3+-oxide minerals made it possible favour oxidized melts, provided be taken out oven before reached: shorter melting time, will glass. shows medieval glassmakers were able overcome challenge making under highly oxidizing conditions retaining enough colours wood-fuelled furnaces.