4 MATERIALS ANALYSIS

Preliminary analysis was carried out to identify the paint fragment materials for guidance they might provide in attributing fragments to various paint layers and in treatment material choices. This analysis also was an opportunity to contribute to the inventory of pigments found in Mesoamerican contexts, the identifications of which often have not been confirmed analytically. Each fragment, no more than 0.5 mm thick, was composed of a white ground layer with one or more thinly applied pigmented layers. The results of analysis by polarized light microscopy, scanning electron microscopy (SEM) with energy dispersive x-ray analysis, and x-ray diffraction analysis methods are presented in table 1. The fragments did not disaggregate in water or organic solvents, suggesting the presence of an insoluble binder in both ground and pigmented layers. However, this finding was not confirmed with either Fourier transform infrared spectrophotometry or ultraviolet fluorescence microscopy, perhaps because of undetectably low concentration. Preserved in the white ground on the reverse of the fragments were minute impressions, the only remaining evidence of the organic material that once served as the substrate for the paint layers. They were examined using SEM, along with comparative materials; the results are interpreted in section 6.

TABLE 1 ANALYSES OF MATERIALS