Through a process called blow molding, the pellet can be used by manufacturers to make new butter tubs. First, the pellet is melted, and then formed into a parison (a hollow, tube-shaped blob of melted plastic). The parison is clamped into the tub mold and air is pumped into it. The air pressure pushes the plastic out into the mold. Once the plastic has cooled and hardened, the mold opens and the new tub is ejected.