TECHNIQUES 8: The wall graze

26 August 2010 | By Lauren Vanderkar

Doug James, director of specialist practice Mindseye, gives expert advice on how to achieve an even illumination across a wall using this architectural lighting technique.

The wall graze can become a great feature in itself, but the effect entirely depends on a range of factors: the light source, angle of the beam, and texture of the wall. “Ideally you want to use a point source – perhaps a low voltage PAR lamp or metal halide with a narrow beam reflector – mounted very close centred and set back from the ceiling line in a trough,” suggests Mindseye’s Doug James. “With the right reflectors it can be done with a T5 fluorescent, but you’ll never get the same effect as you will with a point source.”

Examples

The aim with this technique is to get an even spread of light across the entire wall. Halogen and metal halide pack the necessary punch, carrying light a lot further than fluorescents. But with heightened focus on the environment and reducing carbon emissions, using halogen lamps to illuminate a large space is no longer an option. “At the flagship Jigsaw store in Bond Street, Isometrix reversed the technique by coming up from behind the floor with low watt halogens. But you wouldn’t see them in a project like that today - they use too much energy,” James notes.

At the Dolder Grand Hotel in Zurich, Speirs & Major used point source to illuminate the cobbled walls in the spa area, and Lighting Design International did the same at The Spa at Gleneagles. The result is an even wash of light running down the walls, a very different effect to that produced by fluorescents at the Barbican Arts Centre. However there is one clear advantage to the latter: “With fluorescents you don’t get scalloping, which is an inevitable side effect of point source, so it looks good in that sense. But you still lose that travel of light down the wall,” argues James.

As with several techniques on this list, energy efficient LEDs are being worked into the wall graze. Mindseye is currently using them at a swimming pool to make a feature out of the mosaic back wall. For a decent effect, the LEDs need to be mounted in a continuous row. James recommends collimated LEDs in this case, with an elongation lens to emphasize the wash. “You can get a pretty good effect, but it comes at a cost.” The price of LEDs is certainly a major detractor, as is colour rendition. “LEDs do have a good narrow beam, but they aren’t as powerful as metal halide or halogen. And with the light sources positioned so close to each other, you’d have to manage the heat carefully with ventilation slots.”

As well as retail, wall grazing is a popular technique in lobbies, reception areas and corridors – anywhere that could benefit from a clean light with no overhead fittings: “It allows you to do away with any other ceiling-mounted lighting,” says James. “It’s amazing how much you can illuminate space using light reflected off walls.”

Pitfalls

It’s perhaps no surprise that America started using the wall graze before anyone else. The size of an average building in the US gives lighting designers more opportunity to use this technique, and it is less common in Europe simply because expansive feature walls are relatively unusual. But, as James points out, a wall graze is a simple and effective way to create a point of interest in what could otherwise be a dead space. “It comes into its own when you have a nice large wall with some kind of texture, like rough stone or chain mail. It becomes part of what gives life to the wall.”

But he flags up potential problems with a clean flat wall: “You run this risk of illuminating imperfections. It’s safer when you know there’s going to be some texture.” With the fixtures mounted so close to the wall, using the wall graze to illuminate pieces of hanging art is also unfeasible. The narrow angle of light would produce shadowing with even a small frame, so supplementary lighting would be needed to light the artwork.

The angle of light and the type of light source have a big impact on this technique, largely because the light has to travel a fair distance to evenly illuminate the wall. The distance between the fittings is another important factor, according to James. “Be very careful about what happens when two fittings meet, especially with fluorescents and LEDs. The pattern needs to be kept even along the wall,” he warns.

The texture of the wall and numerous other variables call for thorough planning beforehand. “Test the beam angles and position of the fittings on a mock-up before you start,” advises James. “And it’s always a good idea to ask yourself: does the wall deserve this treatment?”