PH's three-shade system is turning 90. To mark this occasion, Louis Poulsen has launched a copper limited edition of the PH 3½-2½ Floor Lamp.

The 3½-2½ Copper Floor Lamp will be sold for a limited period from 1 October to 31 December 2016.

Designer and innovator Poul Henningsen (1894-1967) developed his revolutionary three-shade system in 1926. Electricity was becoming increasingly common in Danish homes in the 1920s, but lamps had not yet been developed to suit the advancing technology.

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Poul Henningsen's invention of the three-shade system rectified this. The lamps were developed to illuminate the newly built Forum exhibition hall, one of Copenhagen's first functionalist buildings, designed by leading architect Oscar Gundlach-Pedersen. The lamps hung from the ceiling “like white birds flying through the gigantic hall”, as a newspaper wrote in their review of the building.

Poul Henningsen devoted most of his life to taming electric lighting. He based his three-shade design on the logarithmic spiral, in order to make optimal use of the point light source. He was constantly doing calculations and tests. The shape of the shades was determined by the way they had to shape and reflect the light, and the lamp was designed to be glare-free.

Louis Poulsen put the three-shade lamp into production. The Danish manufacturer of lighting, founded in 1874, has established itself as one of the key suppliers of architectural lighting on the world market, providing of range of lamps designed by architects such as Poul Henningsen, Arne Jacobsen, Verner Panton, Vilhelm Lauritzen, Øivind Slaatto, Oki Sato, Shoichi Uchiyama and Louise Campbell