How does gravity cause filtration in a simple funnel setup?

In a simple laboratory funnel setup, gravity acts as the primary driving force for filtration. For a fluid to pass through a filter medium, an external force must be applied to overcome resistance.1

In this configuration, the weight of the liquid mixture placed in the funnel creates a downward force due to gravity. This force pulls the fluid through the pores of the filter medium, while the solid particles—which are too large to pass through the pores—are retained on the filter. While gravity is sufficient for basic laboratory filtrations, it is a relatively weak force compared to other methods; if the process is too slow, a partial vacuum is often applied below the filter to increase the rate of flow.12