I should start by saying that I like to know how things work. My curiosity, however is selective, I have a special fascination for human inventions, the simpler the better. A few weeks ago I helped open one of the gates of a canal lock and it was thrilling to feel that I was working with a device invented over 700 years ago that has changed little since. There I was pushing a gate that looked just like those seen in Leonardo da Vinci’s original design of 1497. However, while da Vinci’s lock system is one of my favourite inventions, there is another that I hold equally dear – the candle (see illustration). Like the lock, this too is an ingenious device, has a long history and its form has changed little since it was first used in China 3000 years ago!
It is the long dark nights of winter that prompted this ‘Ode to the Candle’, a gadget with its ingenious wick-and-wax design that has been unsurpassed in providing we humans with light for millenia. I am not interested in their added colours or complicated shapes nor in their various concocted scents (“Cologne for Men!”), I just love to watch candles as they burn, to see their glow, and to marvel at how they work. Indeed, the mechanism, with all its interlinking elements, could hardly be bettered. No need for any highfaluting chemistry or computer controlling system, the workings rely on the genius of how their different components interact – how simple and clever!
At first sight the candle looks so simple, just a thin stick of wax with a wick running through that protrudes a little at the top end and nowadays bends over to one side. But once the wick is lit, how it can provide enough steady light for hours of reading or working is magical.
Its workings rely on three separate elements; first the wax stick which provides the fuel, secondly the wick which delivers the fuel in a measured way to the third element – the flame.
Starting with the candle’s fuel cell. Any light provider needs an energy source, and here the energy comes, not from a fluid such as oil, petrol or kerosine but from a solid block of wax. By tradition the block has been made of whale fat or animal fat (tallow from beef or mutton) or, best of all, bees wax (as in the candle in the photo). In functional terms this fuel cell is portable, odourless, not explosive, light to carry and, when stored lasts for years – no use-by date here! Moreover, it remains cool throughout its length even when the wick is burning so it can act as a handle. Importantly, where the cell is made of bees wax, the candle flame produces neither smoke nor toxic fumes. In addition, bees wax, which is itself a renewable resource, burns so efficiently that there is rarely any fluid waste that would otherwise trickle down the candle’s sides. Here is an eco-friendly system of perfection.
Now to the wick, the “soul” of the candle which ‘holds’ the flame. It is usually made of a long ‘string’ of wax-impregnated cotton specially braided so that the exposed wick end bends over. To work well the wick needs to be a particular diameter (the thicker, the greater the light) and stiffness (it needs to keep its shape); paradoxically it must also be fire resistant. When the wick is lit, it melts the surrounding wax and by capillary action draws the molten wax up to be delivered in tiny amounts to the candle’s burning end; here the melted wax now vaporises and combusts. In the past, wicks needed regular trimming – long wicks produce more smoke and smells and increase the risk of fire; nowadays, wicks are ‘self trimming. By being bent, it’s tip rests not in the cooler central part of the flame but in one of the hotter side zones where it burns off – as the wick end burns it become bright red (see illustration).
Finally, the flame, which at its centre has a luminous yellow area that generates light. In fact the flame has several well-defined areas with varying temperatures and colours depending on the local oxygen supply and the rate at which the wick delivers its flammable wax vapour. The coolest part is in the central lower luminous area in which sits the wick; the hottest part is the blue-tinged veil which surrounds the upper part of the flame. It is in the veil that any waste is burnt off.
A good way of keeping in touch with the past is through the inventions that have been handed down. Reading by the light of a burning candle offers a perfect reminder.
The illustration shows a photo of a burning, bees wax candle made near our house in France; its golden colour is that of the wax itself.
For helping me write this blog I would like to thank Neil, Agate, Armelle, Sarah and Vivien.