1064 nm DISPERSIVE RAMAN MICRO-SPECTROSCOPY FOR THE IN-SITU IDENTIFICATION OF ORGANIC RED COLORANTS

Raman spectra of red colorants were obtained in-situ using a dispersive Raman microscope equipped with a 1064 nm laser source and InGaAs array detector. By employing near-IR excitation, the fluorescence of organic colorants is significantly reduced compared to visible wavelengths. Spectra presented include alizarin crimson, lac dye, cochineal, brazilwood, dragon’s blood, sandalwood, logwood,and safflower. Analyses of dry pigments versus those applied in binding media are also presented. This work demonstrates that using 1064 nm excitation in a dispersive Raman system may allow in-situ characterization of artists’ materials, including organic colorants, which are challenging to analyze using visible excitation wavelengthsbecause of interfering fluorescence.