The effect of the growth and annealing temperatures on anomalous biref
ringence of solid solutions of alum crystals has been studied. An incr
ease in the growth temperature of alum crystals results in lower biref
ringence values, which favors the hypothesis that kinetic ordering of
cations causes optical anomalies in alum crystals. The kinetics of a d
ecrease of birefringence during annealing is also consistent with this
hypothesis.