The PH Lamp: Poul Henningsen's Glare-Free Louis Poulsen Lamp

Few objects have shaped how we think about artificial light as much as the PH lamp. Designed by the Danish architect and critic Poul Henningsen and produced by the Copenhagen firm Louis Poulsen since the mid-1920s, it is the Louis Poulsen lamp most people picture: a stack of curved shades that hides the bulb completely while spreading soft, even light. A century later, its principle — never let the eye see the light source — still underpins good lighting design.

This article tells that story as design history: the problem Henningsen set out to solve, how the layered shade works, the Paris debut, the later PH 5 and Artichoke, and why the idea matters to anyone designing a room today.

Poul Henningsen and the problem of glare

Poul Henningsen (1894–1967) trained as an architect and became one of Denmark’s most outspoken cultural critics, writing on architecture, design, politics and society. His interest in light was practical as well as aesthetic. The electric bulb had arrived in homes, and with it a new discomfort: a bare filament is intensely bright, and the shades of the day either exposed it or smothered it.

Henningsen’s diagnosis was precise. Good light, he argued, should be free of glare, should fall where it is needed, should model faces and objects with gentle shadows, and should have a warm, pleasant colour. Above all, the source itself should be hidden from normal viewing angles. Every ray reaching the eye should first be reflected off a surface that softens it.

He approached this as an engineering problem: the shape and position of each reflecting surface would be calculated so that light from the bulb was redirected, not merely blocked.

The three-shade system and the Paris lamp

Henningsen began working with Louis Poulsen, then an electrical supply company, in 1924. Their first major result was a multi-shade lamp entered in the 1925 Exposition Internationale des Arts Décoratifs et Industriels Modernes in Paris — the exhibition that later gave Art Deco its name. The lamp won a gold medal.

The production versions that followed from around 1926 used three shades of different sizes, stacked one above another with the bulb positioned at a calculated point between them. Their geometry works in a few ways at once:

The shades overlap so that, from normal viewing positions, the bulb is never visible directly.
Each curved inner surface reflects light outward and downward, so most light reaches the table or floor after a single reflection.
Some light passes through or around the shades, gently illuminating the shades themselves and the surroundings, so the lamp glows rather than appearing as a black object with a bright pool below.
Shade finishes — matt white undersides, coloured or metallic tops — control the brightness and colour of the reflected light.

The three-shade principle became a system. Varying the shade diameters, materials and arrangement produced a family of pendants, table and floor lamps, named by the size of their shades and the designer’s initials, such as the PH 4/3, which combines a top shade of 40 centimetres with a middle shade of 30.

How the Louis Poulsen lamp tames light

What distinguishes the PH lamp from a merely attractive shade is that its curves are functional. Louis Poulsen describes the shades of the later PH 5 as based on the logarithmic spiral, a curve that recurs in nature, with the light source at its focal point. The aim is an even distribution of reflected light across each shade, so that no part of the surface becomes a hot spot.

This is the essence of the Louis Poulsen lamp tradition: light is shaped by geometry rather than by diffusing material. Compare it with the Akari lamp, which achieves softness by making the whole paper shell glow, or the Anglepoise lamp, which concentrates light into a directable beam. All three are glare-free in their own way, but by completely different physical means.

For anyone planning lighting, Henningsen’s rules translate directly into practice: hide the source, light surfaces rather than air, and let the fitting itself glow just enough to read as part of the room.

The PH 5 and the Artichoke

In 1958, Henningsen developed two of his best-known designs. The PH 5 pendant takes its name from its 50-centimetre top shade. It adds an inverted shade above the main stack to light the upper surfaces, and small coloured elements around the light source that soften and adjust the colour of the light. It was designed partly in response to changing light sources: households were switching between bulbs of different shapes and sizes, and the PH 5 was intended to give comfortable light from a range of them.

The same year, Henningsen designed the PH Artichoke for the Langelinie Pavilion restaurant in Copenhagen. Its 72 leaves are arranged in staggered rows around the source, so that every leaf both conceals the bulb and reflects light outward. From below, the fitting reads as a dense sculptural form; lit, it glows from within with no visible source. It applies exactly the same principle as the 1920s lamps on a far more elaborate scale.

Place in Danish design

The PH lamps belong to a broader story of Danish design in the twentieth century, in which careful craft, clear purpose and humane comfort were valued above novelty. Henningsen’s lamps predate the mid-century boom that made Danish furniture famous, but they share its values: an object should do its job exceptionally well, and its form should follow from that job.

They also anticipated ideas that shape interiors today. The emphasis on soft, warm, glare-free light is central to Scandinavian interior design, where long winter evenings make the quality of artificial light a daily concern. The Danish idea of comfortable domestic atmosphere owes a good deal to the kind of light Henningsen championed.

Lessons for lighting a room today

The light sources have changed — LEDs have replaced incandescent bulbs — but Henningsen’s principles are, if anything, more relevant. LED chips are small and extremely bright, which makes glare a more acute problem than it was with a frosted bulb. A fitting that exposes bare LEDs at the edge of vision will tire people in the same way a bare filament did a century ago.

The practical lessons are straightforward. Choose fittings that conceal the source from where people sit. Light walls, tables and ceilings, which then light the room. Use warm, good-quality light for living spaces. Hang pendants at a height where the shade, not the source, is in the eye line. Our guide to pendant lighting ideas applies these ideas to choosing and hanging pendants. As with any fixed fitting, new lighting points in Singapore must be installed by an EMA-licensed electrical worker.

Frequently asked questions

Who designed the PH lamp?

The Danish architect, designer and critic Poul Henningsen, working with Louis Poulsen from 1924. The first multi-shade lamp won a gold medal at the 1925 Paris exhibition, and the three-shade system was refined for production in the years immediately after.

Why is the Louis Poulsen lamp glare-free?

Its overlapping shades hide the light source from normal viewing angles and reflect light off curved, matt inner surfaces before it reaches the eye. The shapes are calculated so that light is redirected, not simply blocked.

What does PH 5 mean?

PH stands for Poul Henningsen, and the 5 refers to the 50-centimetre diameter of the top shade. Other PH lamps are named by the sizes of their shades in the same way.

What is the PH Artichoke?

A pendant designed by Henningsen in 1958 for the Langelinie Pavilion restaurant in Copenhagen. Its 72 leaves are arranged to conceal the source completely while reflecting light outward.

How does the PH lamp differ from a paper lantern?

A paper lantern diffuses light through a glowing shell. The PH lamp shapes light by reflection from solid, curved shades, keeping the source hidden and directing most light downward.

Planning an interior where structure, ceiling and lighting must be resolved together? Talk to our consultancy or get in touch.