To perform experiments at variable interaction potentials, mixtures of oppositely charged PS particles with 4.5 mM NaCl and 0.1 wt% F108 were introduced into 50-mm-long glass capillaries (inner dimensions: 2.0 mm × 0.2 mm, VitroCom) and sealed at one end. The capillaries were then immersed in 100 mm diameter Petri dishes filled with deionized water (Extended Data Fig. ). During crystallization, each capillary was imaged using a Luxonis OAK-D S2 camera, recording a time-lapse with a 10-minute delay between frames (Extended Data Movie 5). The position of the crystallization front was tracked over time using Im-ageJ, by identifying and tracking the boundary between the opaque area of the capillary (gas phase) and the transparent area (crystalline phase). Simultaneously, we tracked the crystallization front by taking microscopy images at regular intervals using a bright-field microscope equipped with a 10X air objective.