Hot water bottle, 1996.
© Science Museum / Science & Society Picture Library
Hot water bottles are made from rubber by compresion moulding. Two blocks of rubber are heated and squashed inside a mould, while at the same time the rubber is formed around a central mould. A stretcher is used to widen the neck and remove the mould once the rubber has cooled. Made by The Haffenden Moulding Company Ltd.