Rebecca Piovesan

X-ray powder diffraction clustering and quantitative phase analysis on historic mortars

This paper describes the application of cluster analysis to X-ray powder diffraction patterns (XRPD) to define homogeneous groups of mortar-based materials according to their mineralogical composition. For this purpose, the diffraction patterns of 110 samples of mortars from the Temple of Venus (Pompeii, southern Italy) were used to test the method. Rietveld refinement, for quantitative mineralogical phase analysis, was performed on the most representative sample of each cluster. The mineralogical grouping yielded by cluster analysis of XRPD data turned out to be consistent with the petrographic groups.

The Polychrome Sinopia of Roman Mosaic at Lod (Israel): Pigments Characterization and Microstratigraphic Study

This paper presents the results of the archaeometric study on the pigments and the painting techniques used to produce the polichrome sinopia found under the tesserae of the Roman mosaic at Lod (Israel). The red, yellow, green and black paints, laying on the sovranucleus of the preparation mortar under the mosaic, were studied by polarised light microscopy on disperse pigments (PLM), reflected light microscopy (RLM), scanning electron microscopy (SEM) and X-ray powder diffraction (XRPD). The palette comprises red and yellow ochre, cinnabar, green earth and carbon black. The microstratigraphic analysis shows the presence of a carbonation layer including the pigment particles on the top of the mortars, indicating that the pigments were laid on a fresh mortar, according to a fresco technique.