In saturated vapor, the aluminumtrihydroxides dissolve in the water and the velocity of dissolution of the trihydroxides becomes larger as the temperature rises. When this solution is supersaturated over the solubility of boehmite, transformation proceeds. The alkalinity and the boehmite added to the hydroxides accelerate the transition. The former makes easy the dissolution of trihydroxides, and the latter acts as the seed and accelerates the velocity of the crystallization of boehmite.