Before the parison cools down, a hollow ramrod is injected into its center and pushed to the top of the mold, stretching out the warm plastic preform as it goes. Compressed air is then forced out in controlled low-pressure stages through the hollow ramrod. The plastic form is forced out to the sides of the mold. Because the stretching is performed evenly, the plastic remains uniformly thin and strong. The soda bottle assumes the shape of the mold and is dropped out of the blow molding machine as the two mold halves separate. A new parison is extruded and the entire blow molding process begins again. The actual manufacture of a soda bottle takes only a few seconds.
Since the introduction of bottled water into the market in the 90′s, it has become a household norm. Blow molding a two-liter soda bottle requires a preformed piece called a parison. The parison is mechanically loaded onto a stand and two sides of a bottle-shaped metal mold come together around it and is usually extruded from a plastic injection mouldplaced very close to the blow molding machine. The warm parison looks like an upside-down plastic test tube, with a preformed collar and threads for the cap at the bottom.