Lighting history

Incandescent light bulbs (lamps) have illuminated the world for more than a century. They’ve done it in a way that has felt natural in historic interiors and has been flattering to the complexion because traditional tungsten filaments provide a spectrum of light not dissimilar to fire or candlelight. Now they’ve been banned in favour of low-energy alternatives. While this will help cut energy bills and carbon emissions, it potentially creates a very different interior ambience and, for anyone with historic fitments, may pose a problem, especially where the light source is visible.

Until recently compact fluorescent lamps (CFLs) were the mainstay of low-energy lighting. These take varying amounts of time to come to full power and are perceived as having a different light quality to tungsten filaments. Now LED lamps, which use light-emitting diodes as the source of light, are seen as the future as they use even less power than CFLs and have the potential to provide high quality illumination. I’ve written about do LED lights for home use impress for SuperHomes.

Despite the virtues of LEDs their output can be different to tungsten filament, fire or candlelight which provide warm and yellow light with a colour temperature range of 1,850 K to 3,300 K. This means that when buying LEDs it’s important to be aware of their colour temperature as some cheap LEDs can give a very blue light – the LED lamps I’ve fitted in my office are 2800 K. It’s also worth remembering that the colour can shift as the lamp ages. Another important fact is that we can no longer equate Watts to light; the actual light output is more clearly stated in lumens.

Another consideration is that clear lamps were used in early electric light fittings and many had a distinct shape. Although there are some exceptions, LEDs rarely have the same profile and some have heat sinks which are visible. It’s also worth remembering the physical impact of fitting these lamps into historic lampholders which may be physically weak or in poor condition

The National Trust has been looking at various options for LED lighting and has blogged about candle bulbs and retrofitting energy saving lighting. Along with the Historic Houses Association, it has worked with Heritage Lighting to develop lamps that will be suitable for lighting rooms and artifacts and will mimic the appearance of a filament.

A consideration with any type of light in an historical context is the potential damage it might do due to heat and harmful emissions. The Trust has tested LEDs from the conservation perspective and, along with other organizations concerned with caring for artifacts, is satisfied that they are no more damaging than any other type of light source that might be used. Indeed, LEDs don’t emit any UV which is the most damaging component of the spectrum and produce considerably less heat than other light sources.