Heating system for the manufacture of plastic articles

In a blow molding machine having an array of generally parallel, vertically spaced heating elements adjacent a path along which a plurality of essentially tubular thermoplastic parisons are conveyed in succession in route to a blow molding station where each parison is blown within a blow mold to form a blown plastic article, a gaseous coolant source for directing coolant gas onto the outer peripheral surface of the parisons as they are conveyed in heat exchange proximity to the heating elements, and means for rotating the parisons while in heat exchange proximity to the heating elements, the improvement of said heating elements consisting of infra-red sources generating a spectral energy peak wave length of about 1.2 microns to completely penetrate the thickness of the plastic parison in order to substantially uniformly heat the parison across its wall thickness at each radial position to within a temperature gradient of no more than about 5.degree. C. to about 10.degree. C., and the heating elements being interposed between said path and the gaseous coolant source.