The Tomba dei Demoni Alati is located in the Etruscan necropolis of Sovana (Grosseto, Southern Tuscany, Italy). At the end of the 1990s, excavation revealed remains of this aedicule tomb, carved into red tuff; in 2004, further excavation highlighted new important figurative elements. The Etruscans used different methods to decorate the rock surfaces of the tomb, which were particularly difficult to paint. For this reason, the porous and irregular surface of the tuff was modelled and coated with specific materials. The aim of this work was to study the materials and manufacturing techniques of the preparatory layers applied onto the rock surface in the Tomba dei Demoni Alati. Minero-petrographic, chemical, and micro-chemical characterization of the layers was carried out. The obtained results suggest that different methods were used to prepare the tomb surfaces to be painted. In particular, in the niche of the tomb, two preparatory layers were found: a Ca-basedplaster covers the rock; above it, a thin white Ca lime layer was applied. In the sculptures inside the niche, the colors were applied onto two finishing white Ca lime layers of similar composition, whereas, in the decorations of the sculptured surfaces on the outside, paint layers were laid onto a thin white silica stratum. The data allow us to determine the use of plaster, for the first time, in Tuscany, as well as the discovery of a preparation layer never before found in any other local archaeological context.