This is purely observation based. Any time I have cooking something on the stove, if I change intensity in any direction - reducing or increasing the heat, it seems like water vapor threads shoot out from the pot.

I can understand if I increase the heat, more energy, but don't have any explanation for reducing the heat. It seems like state change any direction causes some water vapor to release.

Don't think it matters, but it's gas based stove.

What causes the vapor or threads of mist to shootout when there is a change ?

  • Is this coming out from underneath the pot, or from inside the pot?
    – Cascabel
    Oct 9, 2018 at 16:51
  • It seems to be coming from the pot. Observed many many times, but then its a not scientific observation, but a more generic observation
    – user871199
    Oct 9, 2018 at 17:01
  • I'm sorry, I'm not sure we're understanding each other. Does "from the pot" mean from inside, where the food is? (but not from the food? where exactly, then?) Or does it mean from the pot itself? (again, where exactly?)
    – Cascabel
    Oct 9, 2018 at 17:34
  • @Cascabel, you got me. Only thing I know is there is extra activity, I doubt if its coming from under the pot - where the fire/gas is burning. Apart from that, all I see is there is extra activity and sudden plume of vapor when I change the settings. I am not sure how to distinguish it between coming from the pot or cooking food as to me its one and same. To put it simply, there is activity at around 10 inches above the pot and only thing I can reliably say is it's coming from pot - from somewhere. I really doubt if it's coming from any other source than food
    – user871199
    Oct 9, 2018 at 17:47
  • 1
    Just want to say that I see the same thing all the time. In case it matters, I think I see it when I use a non-stick pan. I don't recall if I see it using my copper pans.
    – Rob
    Oct 9, 2018 at 23:27

3 Answers 3


It's hard to say without seeing it, but I suggest that this phenomenon happening when you turn up or down the gas may be caused by your arm reaching out in the vicinity of the pot to turn the knob.

The air above the pot should be saturated with water vapor at a higher temperature. Motion nearby will create eddy currents that carry that moist air to where it can meet cooler air. You see the moisture when it condenses to fog.


I don't know about turning the heat up and your observation, but seeing more "steam" when turning the heat down or off is often wondered about. It was asked and answered on the physics stack exchange. Basically, since "steam" is transparent water vapor, what you are seeing when the cooling happens is a cloud of condensed water vapor. The issue with the observation and answering the questions lies in the difference between true steam and this condensate. There is more information in the link. What you are seeing when you turn the heat off (or down) is the condensation of the water vapor, which obviously happens at a lower temperature than that needed to keep the water vapor transparent (at least most of it...which is way you always see a little of the condensate).

By the way, it looks like there is a duplicate question in physics, as pointed out in the comments above.

  • We have an almost dupe (but only about turning down) here on SA as well.
    – Stephie
    Dec 12, 2019 at 12:26
  • @Stephie...good find, I thought I had seen that, but for some reason couldn't find it this morning. I would say this question is a dupe then.
    – moscafj
    Dec 12, 2019 at 12:46
  • I’m torn - for turning down the heat, yes, but how about cranking it up?
    – Stephie
    Dec 12, 2019 at 12:47

I think what you're observing has a common name in the culinary world. It's called carry-over heat. Assuming you have a big pot on the stove, and the heat source is at the bottom. The bottom of the pot is hotter than the top of the pot; say there's a 5C difference. Bottom is 99C, top is 94C (almost boiling)

Even when you turn off the heat, the heat from the bottom portion of the liquid will continue heating the top portion to an equilibrium between 94 and 99. Say 96; and 96 is already good enough to observe steam on the top.

  • It seems like this explains why you can get steam in general at times after reducing heat, but I don't quite see how it explains why you'd get obvious vapor immediately when reducing the heat, as opposed to just having no change (e.g. vapor before, vapor after).
    – Cascabel
    Oct 9, 2018 at 15:22
  • @Cascabel, if the stove is set at a really high heat, and the moment you reduce the heat; you can just be lucky in the timing of it... (i.e. it was about to happen in a moment, but you delayed it slightly)
    – zetaprime
    Oct 9, 2018 at 15:27
  • Sure. The OP's question implies it's more consistent than that, though.
    – Cascabel
    Oct 9, 2018 at 15:57
  • As there can be many reasons, this is one of them.
    – zetaprime
    Oct 9, 2018 at 16:27
  • As a stackexchange user I always hate to see negative points for any reasons. But as @Cascabel mentioned, its more consistent. Any time I tinker with the heat settings, I see a flume or whip or steam arising. Unless I have some magical skills, these are the observations from my day to day cooking
    – user871199
    Oct 9, 2018 at 16:49

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