Color Assessment of Facing Brick by UV-VIS-NIR Spectroscopy

Diffuse reflection UV-VIS-NIR spectroscopy was used to study changes in the color of facing bricks from the content of the additive of manganese tetraoxide (Mn3O4) into the ceramic mass. This investigation was shown that with an increase of the additive content, both the intensity of the absorption bands of colored bricks corresponding to hematite decreases, and the absorption intensity increases with a shift in the maximum of the wide absorption band from the visible to the near-infrared range of the spectrum. By changing the values of the color coordinates in the CIE L*a*b* and Mansell systems: lightness and color, and the values of the indicator-relative color ability, it is fixed that the color of a brick depends on the ratio of two pigments: yellowish-red of hematite and black, probably jacobsite in its composition.