A second annealing process of silver- or cuprous halide microcrystals containing glass changes their photochromic behaviour. The second-annealing is carried out both below T-g of the glass and below the melting point of the crystals. In situ UV-VIS spectroscopic measurements in this temperature range indicate changes in excitonic peaks of CuBr or CuCl microcrystals as function of temperature, annealing time and cooling rate. Room temperature spectra of irradiated samples show a direct dependence on the conditions of the second annealing process. The decrease in the transition temperature of these small crystals below the bulk value causes partly transitions of the low temperature modification of the crystals into the high temperature modification, that does not contribute to excitonic absorptions and darkening ability.