CONICET | Buscador de Institutos y Recursos Humanos

Carbon-based black pigments are a wide group of dark-colored materials, which are classified according to the starting material used and their method of manufacture. Raman spectroscopy is an ideal technique for the characterization of carbonaceous matter: crystalline carbon materials present well defined peaks, which can be easily assigned; amorphous carbon materials, on the other hand, show broad bands between 1300 and 1600 cm-1. The aim of this work was the discrimination between carbon-based pigments by micro-Raman spectroscopy. Five carbon-based pigments provided by Zecchi (lampblack, ivory black, bistre, bitumen, and graphite), two-humic-earth materials (Van Dyck (Kremer) and Earth of Kassel (Zecchi)) and a commercial wood charcoal were studied. Raman spectra of all the samples showed the characteristic bands at ~1580 cm-1 and ~1350 cm-1, however a clear difference in position, width and relative intensity could be observed for most of the samples. The resulting analysis showed that micro-Raman spectroscopyallowed discrimination of most of the reference pigments and allowed the identification of carbon-based black pigments in two South American colonial paintings dated from the early eighteenth century.