An apparatus for manufacturing articles made of polyurethane that includes a mold assembly in communication with a mix chamber. The mix chamber is positioned below the mold assembly. The mix chamber includes a propeller for mixing the liquid polyurethane chemicals. The mix chamber further includes a pneumatically actuated bladder that causes the mixed chemicals to move from the mix chamber to the mold assembly. The chemicals expand to take on the shape of the mold. The method of the present invention comprises the steps of: (a) selecting polyurethane chemicals having certain specific weights; (b) placing said chemicals in a mix chamber wherein chemicals stratify according to their specific weights to prevent detrimental reaction among the chemicals until final mixing; and (c) allowing the chemicals to expand to form an article.