All waxes are essentially hydrocarbons, which means they are largely composed of hydrogen (H) and carbon (C) atoms.
The line in the middle of the candle is called the wick, which plays the role of liquid wax. When the candle is just produced, the candle wick already has solid wax oil. When you use the candle, the solid wax oil is heated and introduced. After the vaporization, the wax vapor is then ignited by the fire so that the candle is lit.
When the candle burns, it releases heat to allow the solid wax oil below to contain, is sucked up by the wick, and continues to be heated, vaporized and ignited by the above fire to form a cycle.
The heat of the flame vaporizes the liquid wax (turns it into a hot gas), and starts to break down the hydrocarbons into molecules of hydrogen and carbon. These vaporized molecules are drawn up into the flame, where they react with oxygen from the air to create heat, light, water vapor (H2O) and carbon dioxide (CO2).
Approximately one-fourth of the energy created by a candle`s combustion is given off as heat radiates from the flame in all directions.
Enough heat is created to radiate back and melt more wax to keep the combustion process going until the fuel is used up or the heat is eliminated.
It takes a few minutes when you first light a candle for this combustion process to stabilize. The flame may flicker or smoke a bit at first, but once the process is stabilized, the flame will burn cleanly and steadily in a quiet teardrop shape, giving off carbon dioxide and water vapor.
A quietly burning candle flame is a very efficient combustion machine. But if the flame gets too little or too much air or fuel, it can flicker or flare and unburned carbon particles (soot) will escape from the flame before they can fully combust.
The wisp of smoke you sometimes see when a candle flickers is actually caused by unburned soot particles that have escaped from the flame due to incomplete combustion.
The candle is a wonderful thing. After you use it, you will find his wonderful things, and you will not be able to separate from it.