MOESM2 of Seeing red: towards an improved protocol for the identification of madder- and cochineal-based pigments by fiber optics reflectance spectroscopy (FORS)

Additional file 2: Figure S1. FTIR spectra for substrate characterization of all synthesized pigments, including the pigments DYE15046 and DYE15047 from the GCI reference collection. All spectra have been vector normalized for comparison. Reference substrates have been synthesized without the dyestuff using recipes described in Table S.1. For simplicity, only characteristic bands of the references are marked for comparison. (A) Pigments with alumina substrates with varying amounts of carbonate (amorphous hydrated form) and sulfate (light hydrated form); (B) Pigments with calcium carbonate as the main substrate component; (C) Pigments containing wool protein in the alumina substrate; (D) Carmine pigments with little or no substrate similar to pure carminic acid except for the C=O stretch band at 1720 cm−1, which is absent [2, 41, 42].