Lighting our houses has come a long way since the humble candle. What you may not know is that Edison didn’t ‘invent’ the first light bulb – there were numerous attempts by people from around 1802 to create artificial light and the first item that could be properly called a ‘light bulb’ in the way we understand it was invented by a British scientist, Warren de la Rue in 1840. It worked well, but used a coiled platinum filament – which was too expensive for commercial use. Next up came another British physicist, Joseph Wilson Swan. He conducted various experiments and by 1860 had a working prototype, but it’s lifetime was too short to be considered a good producer of light. He kept at it and by 1878 had developed a longer lasting bulb that used treated cotton thread as a filament. In 1874 a Canadian patent was filed by Woodward and Evans. They used carbon rods in glass cylinders filled with nitrogen but were unsuccessful in trying to commercialise their invention and so Edison bought their patent in 1879.
Edison went on to discover that a carbonised bamboo filament could last for over 1200 hours and with that the incandescent light bulb as we understand it was born. It’s served us well for the best part of 130 years, but this original design is finally being phased out across the world in favour of more energy efficient bulbs using different technologies and materials.
Now there are a number of different types of bulb being made and these are explained below.
Tungsten – Incandescent
With only 5% of the energy consumed being used to produce light, these always had extremely poor efficiency and are now being phased out across the world. Yet most of us still use the quality of the light produced by this type of bulb as the benchmark for what ‘good’ artificial light should look like. This may well be because it’s the light older folk grew up with, but they are also very ‘warm’ emitting a yellow-ish light between 2,300 and 2,700 Kelvin (Find out about Kelvin here). This kind of light has an inviting quality and is very complimentary to skin tones.
They usually last between 700 and 1,000 hours, but are fragile and break easily and tend to blow suddenly. They can also be used with a dimmer.
Tungsten – Halogen
These are a variation of an incandescent light bulb. As they burn at a much hotter temperature than ordinary tungsten light bulbs, their casing is made from quartz rather than glass. They are most commonly used in downlights, under cabinet lighting and pendant lights and can be dimmed.
Their light is whiter (or cooler) than the standard bulb at about 3,400 Kelvin. This type of light renders colours much closer to their true value (I.e. as they would be seen in bright sunlight) so are ideal for environments where this is important.
They are more energy efficient than ordinary incandescent bulbs and have low-voltage variants that need a transformer to take the wattage down to 12 volts. There are also ‘eco’ versions available such as the Sylvania HI-SPOT Superia ECO 35W=50W GU10 which have a 30% energy saving over a standard halogen bulb
The mention of these tend to summon up images of the harsh buzzing lights casting very flat cold light in commercial spaces . However, the technology has come on leaps and bounds and domestic versions are now available.
The typical fluorescent light emits a very white (cool) light which is pretty close to daylight, but it’s now also possible to get warmer white and coloured versions. The produce more light and last longer than the standard incandescent light bulb. Mini-fluorescent strips are most often found as under-cupboard lighting in kitchens, adding valuable ‘near daylight’ lighting to work surfaces.
Compact Flourescent Bulb (CFL)
The most common domestic version is the CFL (Compact Fluorescent Bulb). These are very energy efficient consuming a quarter of the energy of a standard light bulb and they last ten times longer. These modern fluorescents are quiet, come on instantly and have warmer, colour-enhanced tones that mean the harsh bright light of the old standard fluorescent strips is a thing of the past.For example the Kosnic 11W Ecolight 2U Stick Bulb comes in very warm white (2,700K)with a brightness equivalent to the old 60w bulbs and an 8000 hours life.
On the downside, CFLs contain traces of mercury which is a toxic heavy metal. The amounts are exceedingly small, but they do need to be handled with care and recycled when they burn out.
Light Emitting Diodes – LEDs
These are taking the market by storm. They are extremely energy efficient and long lasting. More familiar as the lights used in mobile phones, digital clocks and traffic lights, they are also used to light some very special landmarks, including the London Eye during New Year’s Eve celebrations.
The technology used is a semiconductor diode which glows when electricity is applied. They can’t burn out as there is no filament to wear out. They are the most energy efficient light bulbs of all, using 90% less energy than the traditional incandescent.
Up until now the downside has been that they have only been able to provide only directional light, not diffused light, which made them ideal for lighting specific areas e.g under-counter task lighting but not general (ambient) lighting. But fortunately, there is a new generation of LED light bulbs which have all the advantages of LED plus they look and feel like an ‘ordinary’ light bulb and fit into standard light sockets, either bayonet or Edison screw E27.
They are also available in dimmable and non-dimmable versions and light-up immediately unlike some of the older energy saving bulbs based on fluorescent technology. They also come in a range of colours from very warm white to white. This really is a breakthrough in light bulb technology and whilst they are still currently very expensive in comparison to the old style light bulb, they last for up to 15 years.