Evaluation of the chromatic effectiveness of color pigments in restoration materials (Lime and Portland cement)

Abstract

The present work investigates the way in which cementing materials such as lime or Portland cement alter the quality of pigments normally used in coloring mortars for use in restoring stone construction of historic or artistic value. The colorimetric measurements indicated that both conglomerants diminish the chromatic capacity of the most pigments studied, with noteworthy losses of saturation and, in some cases, substantial variations in hue. The most serious incidents involved lead - vermilion and yellow - in both cases the hue shifting towards the orange range. The compositional study of the material by X-ray diffraction (XRD) showed the decomposition of the compound chromophore, thereby accounting for its loss of color stability.