Cleaning PH Lamps: Matt Lacquered Aluminium and Opal Shades

Poul Henningsen designed his lamps around reflected light, so a PH lamp is only as good as the surfaces the light bounces off. This guide explains how to clean matt lacquered aluminium, soft-touch paint, opal acrylic, opal glass and fabric cord without dulling the finish or changing the quality of the light.

Why the white inner surfaces matter

Every PH shade is drawn on a logarithmic spiral. The curve lets light from a single bulb strike the inside of each shade and leave at a controlled angle, so the source is hidden and the room receives soft, layered, glare-free light. Put simply, the bulb lights the shades and the shades light the room. If you want the geometry in more detail, our piece on how the PH three-shade system works walks through the numbers.

That is why the PH 5 Pendant Lamp is made in matt lacquered aluminium with white inner sides whatever colour the outside is. The outer finish is what you see when the lamp is off; the white underside is what you see when it is on. Inside the PH 5 there are also small red and blue cones that subtly refine the colour rendering. On the PH 80 Table Lamp, a concealed red top reflector nudges the light towards the warmth of a candle.

A film of dust on these surfaces does more than look untidy. Matt white is chosen because it scatters light evenly; dust gives it a greyish, slightly textured layer that absorbs some of that light and flattens the gradient from one shade to the next. Treat the insides as the working part of the lamp and the outsides as its face.

Dusting matt lacquered aluminium

Matt lacquer is the finish most likely to be damaged by enthusiasm. Its low sheen comes from a fine surface texture, and anything abrasive (scouring pads, gritty powders, rough paper towels, even hard rubbing with a dry cloth over trapped grit) can polish small areas into shiny patches that never quite match the rest of the shade again. The same care applies to the soft-touch black painted aluminium of the PH 3/3 Pendant.

1. Switch off and let it cool. Turn the lamp off at the switch or wall and wait until the bulb and shades are cool to the touch.
2. Remove loose dust first. Use a soft feather duster or a clean, dry microfibre cloth and work with light strokes, following the curve of each shade from the top outwards. Do the white inner sides as well as the outsides.
3. Lift, do not scrub. For marks that dust will not shift use a microfibre cloth that is only slightly damp with clean water, wrung out until it no longer feels wet. Wipe gently, then dry at once with a second soft cloth.
4. Leave the spacers alone. The PH 5's rolled aluminium spacers hold the shades in their precise relationship. Dust around them, but do not bend or twist them while you clean.

Avoid spraying anything directly onto the lamp. Liquid runs to the lowest point, which on a pendant usually means the lamp holder. Keep the cloth barely damp and the electrical parts dry.

How often? Pendants over a dining table or kitchen island benefit from a light dusting every few weeks and a gentle damp wipe when you see a film. Little and often is kinder to a matt finish than an occasional heavy clean.

Handling opal acrylic and opal glass

Opal shades behave differently. They transmit light as well as reflecting it, so any smear shows as a shadow when the lamp is lit. Check your work with the lamp switched on (once it has cooled and been reconnected, never while you are cleaning), because marks that are invisible in daylight become obvious against the glow.

PH 80: moulded opal acrylic

The PH 80 Table Lamp, created in 1974 for what would have been Henningsen's 80th birthday, has shades in high-pressure moulded white opal acrylic with a polycarbonate top shade. Acrylic is lighter than glass and glows very evenly, but it is softer, which means it scratches more readily. Use only a clean microfibre cloth, dry for dust and very slightly damp with water for fingerprints. Wipe in one direction rather than in circles. Rough fibres and abrasive products will leave fine scratches that catch the light.

The lamp measures 320 x 405 x 320 mm and weighs 6.0 kg, so do not lift it by the shades. Hold the stem or base with one hand while you clean, and move it by the base when you need to reach the back.

PH 2/1 and PH 3/3: mouth-blown opal glass

The PH 2/1 Table Lamp has shades in mouth-blown white opal glass, sandblasted on the undersides for uniform light distribution, and the PH 3/3 Pendant is available in mouth-blown white opal three-layer glass or combined with metal. Glass tolerates a damp cloth well, but the sandblasted undersides of the PH 2/1 need a lighter touch: their fine matt texture holds dust and can hold fibres too. Brush them with a soft, dry brush or a microfibre cloth, and keep any damp wiping to the smooth outer surfaces.

The PH 2/1 is compact at 200 x 355 x 200 mm with a base of Ø120 mm, and weighs 3.4–3.6 kg depending on finish. Clean it on the table where it stands, supporting the shade you are wiping with your free hand. The top plate, base and stem are machined brass in a metallised or high-lustre chrome-plated finish; a soft dry cloth is enough to remove fingerprints.

Cleaning the fabric cord and canopy

The fabric cord is easy to forget and quick to collect dust. The PH 5 hangs on 3 m of fabric cord; the PH 3/3 on 4 m of black textile cord. Always switch off the power first.

• Run a dry microfibre cloth down the cord in one direction, from the canopy downwards, holding the cord lightly so you do not pull on the lamp or the ceiling fixing.
• For stubborn dust, use a vacuum cleaner with a soft brush attachment on its lowest setting, again working downwards.
• Do not wet the cord, twist it or knot it. Moisture can travel along a textile braid, and knots strain the internal conductors.
• Wipe the canopy at the ceiling with a dry cloth. On the PH 3/3 the suspension unit and canopy are matt black powder-coated aluminium, which responds to the same gentle approach as the shades.

On the PH 80 the cord is 2.5 m with a switch on the cord. Wipe the switch housing dry and keep it free of liquid.

A short routine for each lamp

The principle behind all four is the same. Remove dust before it settles into a film, keep water to a minimum, never use anything abrasive and keep liquids away from electrical parts. Kept this way, a PH lamp gives the same even, warm light for decades.

If you are adding another piece to a room already lit by a PH lamp, see the full Louis Poulsen collection for designs that share the same thinking about reflected light.