The present invention provides an apparatus for forming a chemical mechanical polishing pad, comprising a tank with polymeric materials, a storage silo with microspheres and a curative storage tank with curing agents. The apparatus further provides a premix prep tank for forming a pre-mixture of the polymeric materials and the microspheres and a recirculation loop in the premix prep tank for recirculating the pre-mixture until a desired bulk density is reached. The apparatus further provides a premix run tank for storing the pre-mixture, a mixer for forming a mixture of the pre-mixture and the curing agents and a mold for molding the mixture.