How do stacked sieves separate particles by size?

Stacked sieves separate particles by size through a mechanical screening process. In this setup, the screens are arranged in a vertical stack with the largest hole sizes positioned at the top and progressively smaller openings toward the bottom.

When a mixture of particles is placed on the top screen, the assembly is agitated to encourage the particles to move through the successive layers. As the mixture passes through the stack, particles are sorted and distributed among the various sieves based on their specific diameters, with each sieve retaining particles that are too large to pass through its particular mesh size.1

It is important to distinguish this method from the use of molecular sieves, which are porous solids—often zeolites—used to separate substances at the molecular level based on size, shape, and polarity rather than the macroscopic particle diameter sorting performed by stacked mechanical screens.123