Secondary nucleation is a central process in natural and industrial crystallization, yet its fundamental understanding remains limited. The current concept proposes that many new crystals can originate from a complex, semiordered boundary layer at the crystal–solution interface. Here, we challenge this concept and argue that the generation of new crystals following seed addition can be explained without invoking a complex boundary layer. Instead, we advance that secondary nucleation can be described exclusively by mechanisms involving crystal breakage. We demonstrate this alternative perspective on secondary nucleation through analysis of fluid shear-induced secondary nucleation and cross-nucleation experiments. This contribution aims to recalibrate the field’s conceptual foundations and to offer a simpler physical basis for secondary nucleation.
Vrieze et al. (Mon,) studied this question.