Colorimetric cataloguing of stone materials (biocalcarenite) and evaluation of the chromatic effects of different restoring agents

Using measures of reflectance and corresponding colorimetric coordinates (CIELAB, 1976), we established the chromatic characteristics of biocalcarenite material from quarries in Granada (Spain), which has been widely used in historic monuments in this city. We also evaluated the effects on this material of inorganic, silicon-organic, organic and mixed silicon-organic and organic substances, which are normally used as consolidating and/or protective agents. The results obtained show that the biocalcarenite material varies gradually between two extremes of colour, with no discontinuities that could help to establish clearly differentiated groups. Regarding treatments, products such as calcium or barium hydroxide provoke a significant increase in reflectance (whitening), whereas acrylic and vinyl resins and various silicon-organic mixtures have a less marked effect (slight increase in colour saturation). Ethyl silicate and silicone monomer barely modify the initial colour of the material.