quality:correction
Combustion

For a candle to burn, a heat source (commonly a naked flame from a match or lighter) is used to light the candle's wick, which melts and vaporizes a small amount of fuel (the wax). Once vaporized, the fuel combines with oxygen in the atmosphere to ignite and form a constant flame. This flame provides sufficient heat to keep the candle burning via a self-sustaining chain of events: the heat of the flame melts the top of the mass of solid fuel; the liquefied fuel then moves upward through the wick via capillary action; the liquefied fuel finally vaporizes to burn within the candle's flame.

As the fuel (wax) is melted and burned, the candle becomes shorter. The end of the plaited wick bends and get consumed in the flame. The incineration of the wick limits the length of the exposed portion of the wick, thus maintaining a constant burning temperature and rate of fuel consumption. Pre-19th century wicks required regular trimming with scissors (or a specialized wick trimmer), usually to about one-quarter inch (~0.7 cm), to promote steady burning and to prevent it from releasing black smoke. Special candle scissors called " snuffers " were produced for this purpose in the 20th century and were often combined with an extinguisher. In modern candles, the wick is made in such a way that it curves over as it burns, which ensures that the end of the wick gets incinerated by fire, thereby trimming itself.