Bentonite is a silicate composed mainly of montmorillonite. Its viscosity develops when its laminar particles hydrate, as their electrical charges interact with one another. It is normally prepared with fresh water, since electrolytes negatively affect its hydration. ​Its performance can be enhanced by incorporating polymer additives that increase viscosity, optimize consumption, and extend service life. These additives may be incorporated during manufacturing or added later in the plant.

Thanks to its thixotropic behavior, bentonite is essential in drilling operations, as it enables borehole pressure control and stabilization.