Influence of surface roughness on color changes in building stones

The influence of surface roughness on color change in several Spanish building stones is studied in samples of the following: Red Alicante, Black Marquina, White Macael, and Yellow Triana. In an experimental laboratory test (acid attack), we simulated the weathering process and made a comparative analysis between this and the polishing process. Changes in both color and roughness were measured during these processes. In limestones with medium or high chroma (Red Alicante) and both low chroma and lightness (Black Marquina), the total color changes were particularly affected in both the polishing and acid attack processes. On the other hand, in marbles with both low chroma and high lightness (White Macael and Yellow Triana), the total color changes were almost imperceptible in both processes. However, no change occurred in the hue of any of the analyzed stones. Spectrophotometric data showed that color change was due mainly to changes in surface roughness and not to chemical reactions that may have altered the oxidation state of the chromophore in the chromogen of the stone.Contract grant sponsor: Research Project GV-97-RN-14-3 Contract grant sponsor: predoctoral research fellowship from Generalitat Valenciana awarded to D. Benavente