Why does a candle burn?

Most people do not wonder about the scientific theory behind a candle burning because it seems to be a simple concept. After all, all it takes to lit a candle is to put a fire near the wick and let it burn down through the wax. However, it is a little more complicated although there are only two factors that come into play in terms of explaining why a candle burns. In order to burn, a candle needs some type of fuel, which is the wax, and needs a wick which is usually made out of absorbent twine.

Focusing on the wick first, in order to actually burn it needs to pass two tests. First the wick must be made out of some type of absorbent fiber and has to have natural capillary action. Capillary action is the scientific principle that liquid will move against gravity upwards when placed in a thin tube or a material that is very porous such as glass fiber wick (generally used for oil lamps). Given capillary action is a little more expensive to create; most wicks are made out of absorbent fibers. In fact, if you touched a wick before it was waxed you would realize the material is actually quite soft.

Once the wick is lit, in order for any candle to stay lit regardless of it if is a standard candle, floating candle, or tealight candle it needs some type of fuel. In the case of a candle, the fuel is wax which is placed near where the wick is. The wax absorbs the wick into it and the heat from the flame starts to vaporize the wax which burns. This is why when a candle is first blown out a white smoke starts to float through the air which is not smoke at all, but actually the wax vapor condensing.

Throughout the process the candle does not catch on fire the wax does not reach a temperature high enough to ignite in the air. The only place that a candle is hot enough to reach this point is at the base of the flame but the wax is slowly burned at the flame base and only a small amount of wax turns to vapor. This is the exact reason that a candle burns down so gradually.