Blow-moulded plastic 'Tango' drinks bottle, 1997.
© Science Museum / Science & Society Picture Library
To manufacture this type of bottle a hollow tube of plastic (polyethylene terephthalate) with one closed end is put into a stainles steel mould and this is closed around it. Compresed air blows the tube up like a balloon until it touches the inside surface of the mould. As the plastic hardens it takes up the shape and markings on the inside surface of the mould. When the mould opens, the finished container is removed. Made by Constar (UK) Ltd.