The effect of the thermal decomposition of calcium hydroxide, in the 500-800 degrees C range, for CaO production was studied. The produced materials were characterized by X-ray powder diffraction, thermogravimetric analysis, N-2 adsorption-desorption at -196 degrees C, Scanning Electron Microscopy and Diffuse Reflectance Spectroscopy. The produced materials were evaluated in Rhodamine 6G (Rh6G) photodegradation and the effect of annealing temperature, catalyst amount and Rh6G concentration were determined. It was evidenced by the X-ray diffraction analysis that upon annealing an average crystal size was achieved which was in accordance with the Scanning Electron Microscopy and specific surface area results. The badgap values of the samples (5.35-5.53 eV) corroborated their insulator nature. Materials evaluation indicated CaO produced at 700 degrees C was the most active material. Samples were taken after adsorption and the photocatalytic reaction, respectively; indicating that CaO was not the effective active phase but Ca(OH)(2). Being both CaO and Ca(OH)(2) insulator materials, the photocatalytic activity was attributed to an indirect dye sensitization.