The compact fluorescent bulb is a fluorescent lamp in which the tube and ballast are miniaturised. It is a derivative of the mercury vapour discharge lamps developed from the mid-19th century onwards, but the first efficient small-scale fluorescent tubes, folded into a U, were not produced until the 1970s. Their low consumption and long life have made them a viable alternative to the traditional incandescent lamp, which has been gradually withdrawn from sale since 2009. The compact fluorescent bulb contains a small quantity of mercury and requires specialised recycling. Philips developed and marketed the first low-energy lamps in the early 1980s and donated these four models to the museum in 1998. In globular-shaped light bulbs, the fluorescent tube is merely encased in a glass envelope.