The bentonite in the flush fluid lubricates and cools the cutting tools whilst protecting against corrosion. As the drilling fluid generates hydrostatic pressure in the borehole, it hinders fluid and gas penetration.

Although these drilling fluids are also used for simple drilling such as wells, their true potential is only demonstrated for demanding tasks such as drilling for oil and natural gas sources and exploration on drilling platforms.

The drilling liquid conveys the drill cuttings to the surface. When the purge pumps have idle periods, the thixotrophy of the bentonite hinders the stone material from dropping back into the drilled shaft.

As a flush fluid, bentonite seals the drilled shaft from water ingress downwards and at the sides of the shaft. The mineral forms a firm sludge cake on the bore wall which provides the borehole with additional stability. The fine bentonite particles enter into the bore wall, swell and harden. Depending on the constitution of the ground structure, fine and coarse particles are needed.