Abstract: The present invention is for a mixing machine for plasticizable compounds which attaches directly to a molding machine and which is used to color a base material with a color additive. The apparatus receives a base material and color additive for mixing and has a mixing chamber within which the compounds are mixed. The machine has a central impeller which drives a first and second helical flight one of which is right handed and the other is left handed. The material is folded over itself within the mixing chamber before depositing into a molding machine. The mixing chamber consists of a cylindrical housing which has a drive motor attached to one end wall, the other end wall being removable. The housing has a substantial portion of its lower wall remove to form an exit aperture into a downwardly extending funnel.