We blow out candles on a birthday cake and enjoy the mood and aroma of candles for a special meal; but, how exactly do candles work? A candle is essentially an illuminating device made from wax and equipped with a wick. Tallow from animal fat, beeswax from the honeycomb, and spermaceti (crystallized sperm whale oil) finally gave way to paraffin wax. Refined from crude oil, paraffin is a solid hydrocarbon at room temperature and is a close relative of petroleum jelly and asphalt. Who could have known that the first successful oil well, drilled in Pennsylvania in 1859, would produce such an amazing substitute for wax from the sperm whale? When paraffin burns, its hydrocarbons are chemically reacting with oxygen in the air to form water and carbon dioxide. Heat and light are also a byproduct, but the controlled production of light has long been the chief function of the candle. Only the heat initiated by the flame of a match in the presence of oxygen is required to generate the light, heat, and fragrance of the candle.
Candle wicks are made of absorbent twine, generally cotton. The wick must have a strong capillary action in order to absorb the liquid wax pooled at the top of the candle and draw it up the wick. Hydrocarbons are concentrated in and around the wick, while hotter temperatures occur at the outer edges of the flame, where oxygen is supplied from the atmosphere. The flame closest to the wick is a nearly invisible area in which the paraffin vapor is broken down, releasing hydrogen and creating long chains of carbon, which we identify as soot. This burning soot in the yellow luminous part of the flame can be observed when placing a knife blade into the flame. Only the portion of the blade in the yellow luminous area of the flame becomes covered with soot. The hottest temperature is found at the top of the flame. Thus, heated wax becomes liquid wax, which is in turn vaporized by the heat of the flame, and finally it is the vaporized gaseous wax that we see burning. Candle wicks do not actually burn, since the vaporizing wax serves both to cool and protect the exposed wick.
Light a match. Hold the flame next to the exposed wick. Heat melts the wax in and around the wick. Melted wax is absorbed by the wick. A capillary action draws the liquid wax up the wick. Hydrogen and carbon are released from the paraffin vapors around the heated wick. Light is released when the long carbon chains (soot) burn in the yellow portion of the flame. Insufficient oxygen or too much paraffin vapor created at the wick will allow unburned soot particles to escape from the flame. Keep the area around the candle sufficiently ventilated. Heat radiates from the visible flame and is hottest at the top. The white smoke that curls out of the end of the wick, when the flame is extinguished, is paraffin vapor condensed into visible form. A lighted match can rekindle the candle, when contacting the white smoke. Remember, it is the wax vapor that burns. Be careful! Though long burning candles may be the perfect choice for an emergency, most will receive the benefits of candles at a time of their own choosing. Be safe and enjoy your candles!
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