A widely used process for the production of hollow thermoplastic shapes. The process is divided into two general categories: extrusion blow moulding and injection blow molding. These processes are typically used to manufacture plastic bottles and containers. (Modern Plastics encyclopaedia 1995)

• Extrusion Blow Molding: A parison or tube of plastic material is dropped or lowered from an extruder. mould halves close around the parison, which is then expanded against the cavity wall by the injection of air. (Modern Plastics encyclopaedia 1995)
• Injection Blow Molding: A two-stage process where plastic is first injection moulded into a preform. The preform is then transferred to a blow mould where it is expanded. (Modern Plastics encyclopaedia 1995).