There is something I always notice with pans on the stove:

  1. With the burner on, if the pan contains oils, once its temperature crosses the oil's smoke point it begins to smoke. This part I understand.
  2. If I continue to heat the pan, eventually the smoking stops or lessens. I assumed this was because everything that could burn off did, except:
  3. If, after the point where the smoking stops, I turn off the burner, the pan immediately begins smoking heavily again, until its temperature cools back down below the oil's smoke point.

Why does #3 happen? Why does the oil stop smoking, but then begin smoking again the moment I am no longer adding energy to it?

Note that the smoking starts immediately when the burner is turned off -- as in, before the pan has had time to significantly cool down relative to the current temperature and the oil's smoke point (cast-iron, for example, cools a lot more slowly than a thin steel pan, but I see the effect in both). If I quickly turn the burner back on, the smoking will stop again. So it doesn't seem to be directly related to the temperature of the pan, but rather to whether or not I am adding energy to it (and even if it is related to the temperature,I don't understand why it would stop at high temperatures). This is the part that I do not understand.

It doesn't seem to matter what type of oil it is but if it helps to have a concrete thing to focus on let's use canola oil, smoke point ~204C (400F), contains a mix of fatty acids:

  • ~4% C16H32O2 (Palmittic Acid) (Saturated)
  • ~2% C18H36O2 (Stearic Acid) (Saturated)
  • ~56% C18H34O2 (Oleic Acid) (Unsaturated)
  • ~26% C18H32O2 (Linoleic Acid) (Unsaturated)
  • ~10% C18H30O2 (Alpha-Linoleic Acid) (Unsaturated)

Also, I do not know if the type of heat source matters, but I see this both with gas and induction ranges (I do not have an electric range).

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    $\begingroup$ I'm not really sure what to tag this. heat is the best I could come up with, it became thermodynamics. $\endgroup$ – Jason C Feb 2 '17 at 18:10
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    $\begingroup$ Could this be a chemistry question? $\endgroup$ – Mikael Fremling Feb 2 '17 at 21:50
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    $\begingroup$ Might be important to note what type of heating element you're using (open fire, natural gas, electric stove, etc) $\endgroup$ – Aaron Feb 2 '17 at 22:05
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    $\begingroup$ @Aaron I added a note. I don't own an electric range or use them that often, but I do know the effect happens on both gas and induction ranges. $\endgroup$ – Jason C Feb 3 '17 at 5:07
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    $\begingroup$ I too have notices this staged smoke/fog generation and wondered about it without having analysed it to the same degree. I wonder if there are any clues in the wiki article. - en.wikipedia.org/wiki/Smoke_point $\endgroup$ – KalleMP Jan 21 '18 at 12:33

when a gas flame is heating the bottom of the pan, the hot combustion products rise up around the periphery of the pan to form a curtain of rising gas (depleted in oxygen) which prevents mixing of the air immediately above the hot oil with air surrounding the pan. the hot oil reacts with oxygen in the air immediately above it to produce smoke until such time as it has depleted the oxygen in that space and the smoke reaction is extinguished (mixture too rich), and the gas in that zone becomes mostly unreacted oil vapor. The instant you shut off the flame under the pan, the curtain effect vanishes and oxygen can reach the oil vapor once again, and the smoking reaction restarts. Turn the flame back on, the curtain reforms, and the smoking stops.

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    $\begingroup$ I wonder if a similar effect would this also apply if the reaction was a 'fog' and not a smoke? Perhaps the vapours are so hot or rising so fast that they do not allow formation of a cloud even though the vapour is present. $\endgroup$ – KalleMP Jan 21 '18 at 12:30
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    $\begingroup$ I don't know. It would be fun to experiment! $\endgroup$ – niels nielsen Jan 21 '18 at 19:08

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