AbstractThe influence of hydrodynamic conditions on crystallization kinetics and properties of borax crystals obtained in a dual‐impeller batch cooling crystallizer was investigated. The two impellers used, i.e., pitched‐ and straight‐blade turbines, were mounted on the same shaft. Hydrodynamics was analyzed by means of the mixing time values and specific fluid flow patterns generated. Results indicate that wider metastable zones were generally observed at impeller positions characterized by longer mixing times. In those cases, the growth rate constants were lower, resulting in a formation of smaller but more regularly shaped crystals. These findings imply that the dual‐impeller position should be taken into account in order to produce crystals of desired characteristics.