Weathering impact on the colour of building stones of the ‘Gateway of India’ monument

Study of the chromatic changes of the ancient pigments in some wall paintings in Egypt and the procedures of conservation

“…Thus, the increase of the partial pressure of the water vapor on the warmed frescoes causes a flux of vapor toward the indoor atmosphere (Figures 2.7). The actual process of color change begins in the summer season, when the temperature is comparatively high to promote oxidation process, which may result in an increase in L* value (lightness-brightness) if the stone is lighter and also decrease in L* value if it becomes darker due to alteration [Tiwari et al, 2005].…”

“…The degree of brightness also depends on overall color of the stones. For sustainable monument preservation, a suitable technique should be adopted so that the degree of alteration can be easily documented [Tiwari et al, 2005].…”

“…The b* values, as well as the values of dominant wavelength indicate an increasing trend towards yellow. The actual process of color change begins in the summer season, when the temperature is comparatively high to promote oxidation process, which may result in an increase in L* value if the stone is lighter and also decrease in L* value if it becomes darker due to alteration [Tiwari et al, 2005]. The variations in color parameters depend mainly on the state of the altered condition of the stone and the surrounding weathering conditions.…”