Fresco and lime-paint: an experimental study and objective criteria for distinguishing between these painting techniques.

Identification of the painting technique adopted by an artist is often debated in studies on the characterization, restoration and conservation of mural paintings. However, objective criteria to identify the two main lime-based painting techniques, fresco and lime-paint, have not yet been systematically verified on replicas. Replicas were painted following both fresco and lime-painting techniques. A comparison of microstratigraphic sequences and distribution of chemical elements reveals systematic differences between the two techniques, providing objective distinguishing criteria. Samples from the Abbey of Chiaravalle (Milan, Italy) and Pompeii were also analysed, and the results were compared with experimental data to validate the recommended criteria.