Before 1850, lighting in homes and buildings was commonly provided by candles or lamps. Candles were made from bee’s wax. The lamps used whale oil or natural oil (such as olive or flax oil). Lighting could also be obtained from bundles of reeds dipped in bitumen (these were known as ‘torches’ and for this reason in UK and South African English what the Americans call a ‘flashlight’ we call a torch).
Things changed when it was discovered that paraffin (or kerosene as the US calls it) could be used in a lamp and that wax could be made from paraffin. The effect of this was enormous – instead of going to sleep soon after dusk people could stay up longer, and it was possible to study at night. You all would say that the next great lighting invention, the light bulb, was invented by Thomas Edison. In point of fact, this is not so; In 1878 English chemist Joseph Swan patented a lightbulb that used carbonized paper filaments. Thomas Edison followed with a patent in 1879. Swan’s bulbs had a bayonet fitting base; Edisons a screw fitting. For this reason, we call a screw fitting bulb an ‘ES’ bulb which stands for ‘Edison Screw’.
There are a whole lot of things you must and must not do when it comes to lights and lighting and here are a few of them:
1: Remember that all lights have different colour spectra. Colour temperature refers to the appearance of light provided by a light bulb. Different bulbs emit different colour temperatures. Colour temperature is in degrees Kelvin and measured on a numbered scale that provides information on the quality of light that a bulb emits. The scale varies from 2500 deg K (warm white) to 6500 deg K (daylight). Apart from providing the ‘mood’ of an area is important to recall that different colour temperatures make colours appear different. By way of example, if you light up a display of raw meat in a supermarket with cool white fluorescent tubes then the meat will appear grey.
2: Do not let your maintenance team get trapped into changing light bulbs or tubes all the time. Most lights will last a year (not incandescent bulbs but they’re not really used). If you let them burn longer, they will lose light output. The best is to change all light bulbs twice a year: Say 17th December and 1st July. It’s false economy to do this at more frequent intervals and if you do it a longer or shorter intervals or “when the bulb fails” you will end up with an artisan and a helper and a ladder being full time occupied in changing light bulbs which is a costly waste of time.
3: Beware of fluorescent fittings in air-conditioned environments. If kept cool fluorescent lamps burn for a very long time but lose their brightness. Since they are still burning, they don’t get replaced and so they whole area becomes poorly lit. Change them once per year.
4: Beware of fluorescent fittings and moving machinery. If a whole lot of fluorescent fittings are fed from a single phase, they can create a stroboscopic effect which can make machinery seem as if it is standing still. This is very dangerous. Always feed area lights with at least two phases.
5: Mercury vapour, high pressure sodium, low pressure sodium fittings all have one thing in common: after being switched on they take time to get to full brightness. The result of this is that if they are lighting up an area with little daylight then, if there is a power dip, they will all go out and take about five minutes to get to full brightness again. In this time people will be confused, machines will trip and so on and people will not be able to see clearly. Make sure you have a few fluorescent lamps in any area lighting scheme.
6: Lighting up computers: Although computer screens have greatly improved make sure that the ambient light compensates for the screen display. Halogen or incandescent lights are best. You only have one set of eyes – light them well.
By Terry Mackenzie Hoy
