The secondary growth mechanism of b-out-of-plane oriented ETS-4 films was investigated and conditions were established to effectively decouple nucleation from crystal growth. Supported ETS-4 films were prepared by a two-step hydrothermal synthesis procedure, which included direct crystallization of seed layers on supports followed by secondary growth of seed layers. Porous α-alumina and titania substrates were employed as supports. Rectangular substrates were diagonally placed in 10 mL Teflon-lined stainless steel autoclaves. Both faces of these rectangular substrates had identical surface characteristics. Syntheses were carried out at 448 K for 72 hr. Seed layer syntheses were performed under autoclave rotation (72 rpm), and static hydrothermal conditions were used for secondary growth of these seed layers. FE-SEM, X-ray powder diffraction, and energy dispersive X-ray spectroscopy were used for characterization.