Three different salt crystals (K2SO4, KCl, and Na2SO4·10H2O) were produced via batch cooling and continuous crystallization using a bench‐scale crystallization device, in order to elucidate the mechanism of inclusion of the mother liquor as a function of crystal size. The inclusion ratio of the mother liquor was higher at small sizes and decreased with crystal growth. All results were represented by the previously proposed model of core‐aggregation and shell‐growth processes for the three different salt crystals. Crystals with small Vickers hardness aggregated with each other, and the inclusion ratio of the mother liquor of aggregated grown crystals was high for all three salt crystals tested herein.