Apparatus (20) for the dispersion of minute bubbles in a liquid resin material comprises high pressure tank means (21) containing a liquid resin material (M) under pressure; means for delivering (45) at least one agent selected from the group consisting of blowing agents and nucleating agents into the liquid resin material; means for agitating (63) the mixture of liquid resin material and the selected agent within the tank; means for shearing (60) the mixture; and control means (50) for determining the population of bubbles of the agent within the mixture and provides an output signal for controlling operation of the means for shearing, thereby altering the fineness of dispersion of the agent in the liquid resin material as desired. A method for the dispersion of minute bubbles in a liquid resin material comprising the steps of withdrawing a quantity of the liquid resin material and an agent selected from the group consisting of gaseous and liquid blowing agents and nucleating agents from a supply tank; controlling the operation of means for shearing the liquid resin material and dispersed blowing agent, positioned within the supply tank, thereby affecting as desired the size and homogeneity of the bubbles of blowing agent; and, agitating the mixture of liquid resin material and dispersed blowing agent within the tank with the output from the means for shearing to obtain a uniform and homogeneous population of bubbles dispersed in the liquid resin material.