why does the steam coming off a pot on the stove seem to be stronger after I turn the heat down from a boil?


When wet food or water is boiling I don’t see a lot of steam, but if I turn the heat down I see more steam. Why?

In: 15

So steam is invisible. That “steam” you see is actually condensation, which is the steam cooling off and back to visible water vapor. You seem more of it when you turn then temp down because the water is closer in temperature to that transition point.


Steam is condensation, meaning it’s water that’s already in the air, only turning visible because the air has cooled down enough to no longer be able to hold it invisibly.

If the air were warmer, then it wouldn’t condense as much, and you wouldn’t see as much steam.

When you have the heat on high, a really good chunk of that heat is not going into the pot. It’s bouncing off the bottom of the pot, squirting around the sides, and heating the air above and around the pot.

When you turn the heat down, this doesn’t happen as much. The air around above the pot cools down slightly. Cooler air can hold less water invisibly.

Tadah, more steam.

The water in the pot boils into water vapor, a colorless gas. The visible “steam” that you see are tiny liquid water droplets that have condensed and are suspended in the air. This condensation depends on both the surrounding temperature and the amount of vapor that’s already held in the air, although the amount of vapor that the air can hold also depends on its temperature (cooler air has a lower vapor capacity). When you turn the heat on your stove down, the air above the pot cools, lowering the vapor capacity of the air, which means more vapor condenses out as visible water droplets — this seems to me to be the likely dominant effect.

This is one of those everyday science problems that is extraordinarily simply in principle but can be especially tricky to explain correctly. That’s why I got help from a [SciAm Q&A about a steamy bathtub](https://www.scientificamerican.com/article/how-does-bathwater-give-off-steam/). A friendly further reading on water vapor, condensation, air capacity, etc. is this minimal-math [SHSU weather lecture](https://www.shsu.edu/~dl_www/bkonline/131online/f09water/09index.htm).