Multianalytical characterisation of a variety of ultramarine pigments

Eleven different synthetic ultramarine pigments of a set of more than 1300 pigments at the Academy of Fine Arts in Vienna were chosen for a detailed study and comparative analysis. A thorough investigation was done by x-ray fluorescence analysis, x-ray diffractometry, Raman and infrared spectroscopy as well as colorimetry. The S3-/S2- ratio responsible for the hue of the pure ultramarine pigments as well as other compounds influencing the final hue of the colorant were precisely determined for each sample. A correlation between the relative concentration of the yellow chromophore, S2-, and the hue of the pigment has been established and the correlation between the color saturation of the pigment and its hue was determined.