Technological features of Cotto Variegato: a petrological aprroach.

The ‘Cotto Variegato’ are tiles used in Lombardy, between the XVII and XIX centuries as flooring for several historical buildings. Tiles are produced by the processing of two compositionally distinct clays. The main stylistic character of these tiles is a banded texture producing a veined aspect, in which white and red bands are also folded. The artefacts were hand crafted using two clayey raw materials of different composition, that are only partially mixed before the firing. The colour differences are produced during the firing. In all samples white and red portions are always composed of Ca-rich and Ca-poor clay, respectively. The multi-layered texture was obtained by a multiple folding and pressing process of the mixture. The interference of fold limbs with the tile surface gives the ‘variegato’ style to tiles. The paper explains how basic petrological knowledge can be applied to the study of ceramic artefacts in order to define provenance of the raw material, firing technology and how ancient craftsmen transformed the natural clayey materials into floor tiles. The methodological approach is that commonly applied to the study of the rocks and consists of textural analyses, at a different observational scale, combined with X-ray powder diffraction, X-ray fluorescence and microprobe analyses.