The three-tone system in Sant Climent de Taullwall paintings: An imprint of medieval treatises

Medieval texts describe the use of the three-tone system as a pictorial procedure characteristic of Ro-manesque art to represent shape and volume. Some Medieval art treatises provide detailed instructions of its application, using specific names for each of the carnation colours: membrana (mid-tone or base colour), rosa and posc (darker) and lumen (lighter). In this study we have verified its use and application by analysing the mural paintings of the central apse of the church of Sant Climent de Taull (Catalonia), currently on display at the Museu Nacional d'Art de Catalunya. A combination of microanalytical tech-niques, micro-infrared spectroscopy (& mu;FTIR), synchrotron-based micro-X-ray diffraction (& mu;SR-XRD), Scan-ning Electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS), and Optical microscopy (OM), provided precise information on the composition and distribution of the compounds in the se-quence of micrometric layers. We have identified the use of up to eight different pigments carefully mixed, to obtain a variety of tones in accordance to the recipes given in the Theophilus' De diversis Artibus and the Hermeneia (Byzantine pictorial tradition). The inner layers, painted directly on the still wet lime mortar, show the typical carbonation microstructure of fresco, while the surface layers for the contours of geometric decorative elements and figures which required longer working times, were applied al secco. & COPY; 2023 The Authors. Published by Elsevier Masson SAS on behalf of Consiglio Nazionale delle Ricerche (CNR). This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ )