Both the disperser and the agitator will mix. Mixers are sometimes compared to pumps. The performance of a pump is usually measured in the horsepower (HP) required for its gallons-per-minute discharge capacity. A high-speed disperser is a high-powered, low-volume pump. Considering its substantially higher horsepower per gallon requirement, a disperser is an inefficient mixer. An agitator is a low-powered, high-volume pump—it is an efficient mixer. A typical dispersion application (such as dispersing pigment to make paint) requires about 1 HP for every 10 gallons; in contrast, an agitator application (such as thinning the pigment dispersion with solvent) requires about 1 HP for every 100 gallons. Although the agitator is the more efficient pump, it does not create sufficient shear to disperse most solids into the liquids.
Moderate-shear high-speed dispersers operating at about half the normal blade speed of high-shear dispersers are sometimes used in place of agitators when some shear is required. Typically, the discs have larger teeth to promote better pumping and require about a third of the horsepower of a high-shear disperser but still three times more than an agitator.