Abstract: Apparatus for the refinement of colloidal asbestos dispersions comprises a horizontally disposed cylindrical tube having a plurality of closely spaced holes around the periphery thereof, a helical screw disposed within the tube, and a flanged jacket concentric with and spaced outwardly from the tube. A slurry of unrefined dispersion is continuously fed into the tube to fill it. Refined slurry is drawn through the holes by a suction pump connected to the jacket while contaminants are retained in the tube and moved by the screw to the outlet end of the tube where they are compacted and removed as sludge through a spring loaded discharge door.