Abstract: An apparatus for the thermal pressure forming of plastic blanks into containers includes several elements. A heater brings the plastic blanks to a melt phase by heating them to a melting temperature sufficient to relieve internal stresses therein. A conveying arrangement takes the plastic blanks through the heater. This conveying arrangement includes a device for preventing the plastic blanks from reaching the melting point only along their outer peripheral edges so that the plastic blanks maintain dimensional stability. Thereafter, a press forms the plastic blanks into retortable containers.