Chromaticism differentiations: A study of the diversified aesthetic appeal of the Ghiandone granite range

This paper presents the results of the study of the change in colour of the Ghiandone granite, which is typically used for ornamental purposes, and of all its mineral constituents, whenever undergoing different surface finishings. Changes in roughness as well as gloss were recorded, and put in relation to CIE colour parameters. The study was carried out by using a spectrophotometer, in order to measure the colour coordinates in CIE L*a*b* and CIE L*C*h colour spaces of those stone samples which have been treated following traditional methods (i.e. polishing, bush-hammering and flaming) and advanced technologies (i.e. pure water-jet and abrasive water-jet); sawplane surfaces (from traditional gangsaw and diamond disk) were also considered in this study. The results show that lightness (L*) is the colour coordinate that experiences a higher variation when different surface finishings are applied, especially bush-hammering. In the CIE L*C*h colour space, polished and pure water-jet finished samples are characterized by higher chroma values than the others samples which are featured by higher lightness. Hue doesn’t show any significant variation. When the total colour difference (ΔE*) is measured, pure water-jet also preserves the original colour of stone and minerals, similarly to the polishing. An inverse correlation between specular gloss values and mean average roughness have been documented.