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INCANDESCENT LIGHT THE HEALTHIER ALTERNATIVE? INCANDESCENT LIGHT HEALTHIER ALTERNATIVES THE The fact that incandescent light matches natural sunlight much better than any other types of lighting seems to support a small body of scientific and anecdotal evidence that it is the healthier option. Part 1 of 2 by Inger Lorelei © 2003 Email: ingerlorelei@tiscali.se ver the last couple of decades I've had a growing suspicion that fluorescent light may not be very good for our health, and that incandescent light may be much better. However, it was not until my training and work as an interior design colour consultant in the early 1990s that I learned that fluorescent light really is quite inferior in quality compared with incandescent light, and I have since spent much time trying to find out what else sets them apart. So let's begin by looking at the technical differences between incandescent and fluores- cent lamp types. * The incandescent light bulb, Edison bulb or GLS (General Lighting System) lamp, consists, as most people probably know, of a glass bulb in which a spiralled super-thin tungsten filament is heated by electricity until it glows. It is kept glowing at a slow, even pace by the bulb having been emptied of air and instead often filled with an inert gas like argon. As implied by its name, this is a form of firelight—exactly the same natural ele- ment as in sunlight or candlelight, only concentrated and safely contained. This is the first reason why incandescent light may be healthier. * The halogen lamp is a smaller, more compressed incandescent lamp made out of thick heat-resistant quartz glass into which a halogen (usually bromine) is added which creates a recycling process of the tungsten particles that makes the halogen lamp give about twice as much light and last 2-4 times longer than a standard GLS lamp. Besides the tiny low-voltage bulbs usually used in spotlights, fairy lights and car headlights, there are also mains-voltage lamps (that give only about 20% more light but don't require a transformer). These usually come in the form of a mini tube, but some of the newer ones have outer bulbs that resemble GLS bulbs and have the same kind of socket. * The fluorescent light-tube, invented in the 1930s, is a glass tube filled with a gas like neon or krypton and some mercury vapour. At each end it has an electrode connected to ballasts in the fixture that rapidly turn them on and off to create a continual series of elec- trical discharges which make the mercury atoms produce an excess of energy in the form of ultraviolet (UV) light. This UV-C light is then turned into visible light by a combina- tion of phosphors which form a fluorescent layer on the inside of the tube. Synthetic light is what I would call the product of this complicated process. Its main advantage is that it gives more light per watt than both GLS and halogen lamp: * The high-intensity discharge (HID) lamp works in a similar way, but in most of these it is mainly the gas that produces the light directly. It is shaped like a mini tube or a large elliptical bulb that requires special fixtures and ballasts, and is often used outdoors. Measuring the Differences There are certain ways to measure the differences between the various types of lights. * Spectral Distribution (SPD) refers to which wavelengths of the spectrum are present, and in what proportions, in the light from a given light source. This in turn determines both the colour of the light and its colour rendering capacity. * Colour Rendering Index (CRI) is a measure of how accurately the colours of an illu- minated object or surface can be seen compared with how they look under a reference light, and is usually divided into five categories of quality: CRI 90-100 is "accurate" (more or less); CRI 80-89 is considered "good" (or "fairly good"); CRI 60-79 gives mod- erate colour rendering; CRI 40-59 has poor colour rendering; and CRI 0-39 is very poor. * Correlated Colour Temperature (CCT) is measured in degrees Kelvin (K). Just as a smith can tell what temperature the metal is by looking at the colour (the hotter it is, the APRIL — MAY 2003 NEXUS = 35 by Inger Lorelei © 2003 Email: ingerlorelei@tiscali.se www.nexusmagazine.com