Analysis of pigments and inks on oil paintings and historical manuscripts using total reflection x-ray fluorescence spectrometry

Old oil paintings and illuminated historical manuscripts are valuable objects of cultural heritage. Pigments and inks once used for these artefacts today allow insights of art historical or archaeological relevance. For their identification, a number of non-destructive spectroanalytical methods can be applied. This paper first gives a historical review and describes fundamentals of optical and x-ray fluorescence spectrometry including instrumentation and analytical characteristics. The variant of total reflection x-ray fluorescence (TXRF) is shown to be a highly convenient tool for the characterization of inorganic pigments and inks. Since only micro-samples are needed, a very gentle sampling technique can be applied. It consists of rubbing a dry cotton-wool bud (Q-tip) over the painted surface without causing any visible damage. Only a minute amount of a few micrograms is removed from the object, transferred to a glass carrier and analyzed by TXRF. Some remarkable examples of TXRF analysis of old paintings and illuminated manuscripts are given. Rather than emphasizing the analytical details, the archaeometric potential of the method is illustrated.