Why Do Candles Produce More Smoke After They are Blown Out?

Why Do Candles Smoke More Once Blown OutEver blow out a candle and ponder why so much extra smoke is produced than when it was lit? Why does this happen? Interestingly it has very little to do with smoke.

As a candle burns, it produces enough heat that the wax of the candle is entirely combusted into CO2 as well as other gas-only products. Any of the wax-vapor that has not been combusted is still affected by the heat and will spread out due to natural convection. As to be expected, though, when the candle is blown out, this causes the temperature to drop, meaning the wax on the candle will not be hot enough to continue combusting. Many people think that the smoke they see after blowing out a candle is a gas, but in all actuality it is not. It is solid liquid wax in the form of tiny droplets. You can think of it as similar to the tiny water droplets found in a cloud. So once the candle is blown out, the wax-vapour in the air has no other place to go rather than in the air as smoke.

Lets Break Down Why A Candle Puts off So Much Smoke After its Blown Out

When you light a candle, the entire candle does not become hot. Instead, only the melted wax at the top of candle is hot. Where the wick sits in the candle, the wax becomes “boiled”; this boiling results in the release of flammable gas. And while the wax itself is very hot, the flame on the wick is even hotter, so hot in fact that the gas burns, which releases heat; this is the process of how the candle continues to burn.

Candle-burning process is as follows:

  • Top of the candle melts due to heat of the wick, thus boiling occurs at the wick.
  • This keeps the flame hot enough so it continues to burn in a gas, flammable form.
  • The air continues flowing as hot air rises, causing the heat in the burned gas to rise upward. As it rises upward, it draws in fresh air that contains oxygen.

One of the neatest aspects of a burning candle is that the flame supports itself. It draws in fuel, expels the fuel and air as well as draws in fresh air; all of this takes place without any moveable or mechanical parts. But what happens when you blow it out? Once the flame is gone, there is not enough heat to keep burning the gas. Still yet, though, even though the flame may not be present anymore, the air is still rising and drawing in new air and the wick itself is hot enough to continue boiling new gas; this new gas, however, does not have a flame to connect with, meaning it will meet cool air and rise in the form of smoke.


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