The heat is on: Raman spectroscopy for the study of repurposed industrial paint coatings on contemporary sculptures

The paint coatings of two scrap metal sculptures by Gonçalo Mabunda were analyzed using XRF, μRaman, and FTIR spectroscopies. These complementary techniques were employed to investigate the materials and degradation processes of recycled paint-coated metals in an art context, an emerging field for material and preservation studies. XRF and μRaman spectroscopies offered detailed insights into the composition and degradation mechanisms of modified industrial materials. These analyses enabled the identification and characterization of several pigments, including phthalocyanine blue and green, chrome yellow and yellow-orange, titanium white, red iron oxide, monoazo red, and yellow goethite, typically used in industrial paint coatings. Alkyd and barium sulfate were identified as the binder and filler in most paint coatings using XRF and FTIR spectroscopies. The stratigraphic study of the paint samples revealed a unique multilayer coating—a silica-lined retroreflective sheet—previously uncharacterized in conservation studies. The analysis of this material offers important insights that may contribute to the conservation of artworks utilizing retroreflective sheets. The combination of colorimetry, ATR-FTIR, and μRaman provided valuable information on the degradation of paint coatings when exposed to heat during the sculptures' assembly process. Results indicate that while a coating's binder may begin to degrade at certain temperatures, the pigment may remain stable. These findings lay the groundwork for a collaborative database on the composition of paint coatings and the definition of effective conservation procedures for painted scrap metals in art and industrial heritage contexts. Overall, this study demonstrates the utility of Raman spectroscopy in conservation research for industrial materials that have been repurposed as art, and its importance in advancing understanding in this novel and rapidly growing area.