A multi-technique approach to the chemical characterization of colored inks in contemporary art : the materials of Lucio Fontana

The present study aims to the characterization of the materials at the disposal of the artist Lucio Fontana. In particular, several analytical techniques were employed to determine the chemical composition of thirteen inks found in Fontana's studio in Milan. Synthetic dyes responsible for the different shades of the inks were identified mainly by means of conventional Raman and surface-enhanced Raman spectroscopy as well as by high-performance liquid chromatography. Indeed, rhodamine-based dyes, often in mixture with yellow colorants such as metanil and acridine yellow, or monoazo dyes were detected in red and ochre inks. Triarylmethane and phthalocyanine molecules were identified in green and blue inks, while the azine compound nigrosine was found in a black ink. The presence of binders, such as gum Arabic and shellac, was instead detected in ink formulations by means of Fourier transform infrared spectroscopy. Moreover, an evaluation of the possibility to perform non-invasive analyses for the characterization of such materials was carried out by means of micro-Raman and reflection FTIR spectroscopies, resulting successful only for selected dyes. On the contrary, non-destructive analyses by reflectance spectroscopy and spectrofluorimetry allowed to start building a spectral database of such materials, potentially useful also for field investigations. More generally, the entire study allowed to obtain important information for future analytical work both on Fontana's paintings and on colored inks used in 20th century art.