An improvement in an apparatus and a method produces a particle dispersion by processing a particle-carrying feedstock passed from a supply vessel through a bed of media contained within a containment wall having an inlet end and a longitudinally opposite terminal end. An auxiliary chamber surrounds the containment wall so that the feedstock is passed from the bed of media, through the containment wall and into the auxiliary chamber while the media is contained within the bed of media. An external pumping mechanism established a pressure differential that draws the feedstock into the containment wall and through the bed of media, then through the containment wall into the auxiliary chamber, and then out of the auxiliary chamber at a location juxtaposed with the containment wall between the inlet end and the terminal end, while maintaining a negative pressure within the supply vessel and within the auxiliary chamber during processing of the feedstock.