A modified Kapitza method used in the study of conditions favorable to the growth of single crystals of zinc (99.99+percent pure), shows that the ratio of the temperature gradient (across the interfacial boundary between the liquid and solid phases) to the rate of growth of the crystal must be maintained within an optimum range of values, depending on the angle of orientation. Optically mosaic crystals give no indication of a preferred region of growth and can be obtained over a much wider range of conditions.