In 1924, Sophus Kaastrup-Olsen, then head of Louis Poulsen, met Poul Henningsen: architect, designer and an endlessly curious mind. From that encounter came an idea that would change lighting forever. The goal was clear: to create glare-free light, able to coexist with both space and people. Two years later, in 1926, that vision took shape in a system that remains a reference today: the PH System.
Henningsen didn’t just design a lamp, he came up with a whole logic. A structure based on three shades working together to control light. The result: soft, balanced and fully functional lighting. A solution that still feels strikingly relevant a century later.
At the core of the PH System lies the logarithmic spiral, a geometry found in nature, from seashells to plant growth. By shaping the shades according to this curve, Henningsen managed to layer the light, removing harsh contrasts and preventing glare.
Each shade serves a precise function: the top one emits the main light, the middle one redirects and softens it, and the lower one shields the eye. Together, they create a warm and natural light, close to daylight yet with the intimacy of candlelight. A balance that’s still hard to achieve today.
All PH lamps follow a very specific naming system: PH 4/3, PH 3/2…
The first number refers to the diameter of the top shade in decimetres. The second defines the combination of lower shades.
This system goes beyond a technical detail, it’s part of the design’s DNA. It helps you understand scale, proportion and light behaviour before even switching the lamp on.
Talking about the PH System means talking about one of the key milestones in lighting design. It’s not just about aesthetics, but about how light shapes the way we live in spaces.
Today, this system remains a go-to reference for architects, interior designers and design lovers looking for coherent, long-lasting and well-thought-out solutions.
At BioscaBotey, Poul Henningsen’s legacy is still very much alive.
Visit us and discover the PH System and other iconic Louis Poulsen lamps at our store on C/Princesa, 52 (Barcelona). See you there!
