Abstract: A male member has a cylindrical core with an internal poppet that is displaced by air pressure to open an air passage for pressurized air to an end of the poppet. The female cavity and poppet form a container bottom wall. A thermoplastic copolymer polyethylene is injected into the mold at about 470.degree. F., the mold having a surface temperature of about 100.degree.-130.degree. F. and the plastic material a temperature of about 130.degree.-160.degree. F. at the time of ejection of the container from the mold. Ribs are formed at the container rim having a depth such as to cause the container to stretch about 6% when removed from the core. The ribs outer edges are coextensive with the container side wall. A lid engaging lip is formed at the container rim edge. The process has a preferred 14 second cycle time and uses a core with no draft. The mold surface is maintained at the desired temperature by a cooling water circuit in the mold.