Evidence of the Use of a Dye Chemically Related to Commelinin in Mesoamerican Codices

Non-invasive analytical campaigns carried out on several Mesoamerican codices pointed to the presence of a blue dye (and associated hybrid pigments) different from Maya blue, the most widespread blue painting material used in the artistic and cultural products in Mesoamerica. The scientific and historical literature suggests that the dye is chemically related to commelinin, an anthocyanin extracted from the blue petals of the Commelina species. UV-vis and FTIR reflectance spectroscopy have been used to identify the spectral markers of the petals extract, and its hybrid pigments, for non-invasive identification. Furthermore, since some Commelina-based painted areas appear highly faded and degraded, artificial ageing tests were performed on laboratory mock-ups to investigate this phenomenon. Spectroscopic and colorimetric analyses were performed to follow the degradation process upon light exposure. Preliminary results indicated that different techniques for colour preparation were employed by the codices’ painters. These technologies are most probably responsible for the different extent of degradation which is experimentally observed.