How a Candle Burns

Candles have been around for centuries, and they will probably be here for just as long as mankind is walking this time-bomb of a planet. When electricity fails, batteries can be a mans’ best friend. But when the batteries die out, and there are none available, there is always the candle to rely upon, as they will always light up the darkness, as long as there is oxygen in the atmosphere (oxygen is required to fuel a fire). But, how a candle burns is not what you would think.

A candle is made up of two parts; the wick, which is made up of some absorbent twine, and the wax itself, which is nominally paraffin wax, which is made from crude oil. The candle will burn as long as there is a wick still present, and some wax surrounding it. Once the wax from the candle has been used up, it is not re-usable, as it was made from crude oil, and the flammable hydrocarbon has been extracted from it.

A candle’s wick will soak up the melted wax, all the way up to the top of the wick. When you first light a candle, you have to tilt the candle sideways a bit, so that the wax can be heated, allowing for the fumes of the burned wax to light, as it is the fumes that cause the flame, not the actual wax itself. The tiny bit of wax that is on the wick is hot enough, from the lighting source, or from the heat of the burning wick, to ignite the candle’s flammable element and allow it to burn. The wick itself does not burn as the candle does, as the vaporizing wax cools the exposed wick at the top of the candle, and protects it. The fumes of the paraffin wax is what causes the flame, not the wax or the wick itself.

A trick you can try at home to verify this would be to take a drinking straw, cut it to about two inches in length, and hold it at a 45 degree angle from the candle, at the base of the wick, or the top of the wax, while the candle is lit. Light a match or lighter, and hold the flame at the opening of the straw, the fumes will light and burn from the top end of the cut straw, with no wick present!

Along the same lines as the first experiment, you can blow out the burning candle, after about five minutes of burning, with a lit match or lighter at the ready. When the candle is blown out, there will be a light trail of white “smoke” coming from the wick. Light the top of this stream of white smoke, and the flame will race down to the wick and re-light it.

These experiments prove that it is not the wax itself that causes the burning, but it is the moisture soaking wick, soaking up the oil from the melting wax, and releasing the fumes of the oil-based wax that causes the flame.