Abstract: A mixer for viscous liquids having an inlet for connection to a pressurized source of the liquids and an outlet for the mixed liquids. A series of chambers are arranged between the inlet and the outlet, these chambers being separated by several convergent/divergent surfaces providing narrow openings between said chambers. The openings are in the form of slits defined by the inner edges of dies which also form the convergent/divergent surfaces upstream and downstream of the slits. The chambers include parallel sided portions which allow for quiescent flow of liquid through these portions. At least some of the dies are movable to adjust the width of the slits. Preferably, the dies and chambers are annular and concentric, and the liquids pass radially inwardly through the narrow openings during mixing and are subjected to increasing stress as they progress through the slits.