Looks can be deceiving: not just chalk in chalk. Analysis of the materials of Madonnari art by XRPD and ATR-FTIR

The characterisation of painting materials is a very special aspect aimed at a greater understanding of the painting technique adopted, the definition of different types of workability and the durability of the artwork. This last feature is the peculiarity of Madonnara art: a particular ephemeral category of street art that entails the use of materials not intended to last over time. The study first involved the professionalism of curators and artists involved in the Arte Madonnara Festival, conceived in 1973 in Grazie di Curtatone (Mantua, Italy), where a 24-hour international art competition takes place annually [1]. Usually, these street paintings are realised on the cobbles or asphalt, nevertheless there is an increasing intention to use mobile substrates, consequently, can be preserved and musealised. Within this research, for the first time, both home-made materials, reclaimed materials and commercial ‘chalks’ used by some Madonnari artists were investigated. The techniques adopted were X-ray Powder Diffraction (XRPD) and Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR-FTIR) (Fig. 1), here combined because providing complementary information. XRPD detected inorganic components, in which the diffractometric patterns obtained can be traceable to crystalline phases. ATR-FTIR enabled the identification of organic dyes and pigments together with any other organic components such as modifiers and stabilisers. The result was a great heterogeneity observed in commercial pastels in which several fillers other than chalk were identified such as barite, kaolinite, calcite, and talc. Also, a certain variety occurred for the different dyes and pigments identified. Moreover, the prevailing minerals of the recovered materials and the composition of the home-made pastels were defined, which were matched by considerations of ease of colour application then related to composition [2]. [1] Artoni P., 2014. I Madonnari a Grazie. Appunti per una storia del primo concorso al mondo di pittura su asfalto, Curtatone. I segni della storia. Mantova, Editoriale Sometti 71-89 [2] Artoni P., Bertelli P., Bottoli M., Pojana G., Cimino D., Labate M., Aceto M., Agostino A., 2023. Conservare l’effimero : il colore dei Madonnari, XVIII Color Conference 2023