How Does It Work
When you light a candle, a lot happens! Heat melts wax close to the wick and the melted wax flows up the wick by capillary action of the wick material. The wax is vaporized (becomes a hot gas) and its hydrocarbons break down into into hydrogen (H) and carbon (C). The now gaseous wax burns in oxygen (O) to produce water vapor, carbon dioxide, heat, and light. The “smoke” from a candle is a very complex material. You probably know it contains a substance called “soot” which is a black material composed mostly of carbon that comes from burning organic items. (You can see soot on surfaces near or over candles and at the top of glass coverings around them.) It’s interesting to note that the yellow flame you see on a candle is comprised mainly of burning soot. What you don’t see is the blue flame surrounding it in which the temperature can be around 2,500°F (1400°C ).
Another component of the smoke from a candle is unburned wax vapor. This is the material that causes candle wax to appear white or gray. For a few seconds, its temperature is high enough that it will combust (burn) with the touch of a flame. It rises, of course, because it’s hot so you will probably need to be above the wick to light it. The smoke trail is very straight when they air is still and you can touch the flame to any part of the trail that’s connected to the wick. The wax vapor reignites and the blue flame travels along it to the wick where the candle burning process starts all over.
