# How do the number, size, and rate of steam bubbles relate to a pot of water's heat? **URL:** \ **Category:** Factual Questions\ **Created:** [September 24, 2015, 8:39pm UTC](https://boards.straightdope.com/t/how-do-the-number-size-and-rate-of-steam-bubbles-relate-to-a-pot-of-waters-heat/732425 "2015-09-24T20:39:14Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [September 24, 2015, 8:39pm UTC](https://boards.straightdope.com/t/how-do-the-number-size-and-rate-of-steam-bubbles-relate-to-a-pot-of-waters-heat/732425/1 "2015-09-24T20:39:14Z")
I ask as a cook in practice, but for the chemistry/physics GQ SD. I believe Lord Rumsfeld, who ought to know a lot about stoves, was the first to point out that turning up the flame when the pot is already bubbling furiously is a waste of flame. 1. How does the evaporation rate and size of bubbles reflect the temperature and heat of the liquid? 2. Does the distinction of temperature and heat have any bearing, and/or am I just showing off? The range of discrete cooking temperatures for different applications is quite large around 212°F, and commonly (except for sous vide-ing) judged by the bubbles. Old recipes say “boil fish,” but what they mean, or should mean, is keep them at a temperature where one or two big 'ol lazy bubbles make their appearance every few seconds–“poached,” and the French use the nice word “smiling” for that; when the water is slightly lower in temperature, on the verge of a bubble, that different state is called “trembling.” I’ve read many (lay) works on the chemistry and physics in cooking, but none have addressed the physics when observing the different states of boiling water . ---
**Author:** ![Smeghead](https://avatars.discourse-cdn.com/v4/letter/s/f1d935/32.png) [@Smeghead](https://boards.straightdope.com/u/Smeghead)\ **Post date:** [September 24, 2015, 8:55pm UTC](https://boards.straightdope.com/t/how-do-the-number-size-and-rate-of-steam-bubbles-relate-to-a-pot-of-waters-heat/732425/2 "2015-09-24T20:55:13Z")
In the ideal system beloved of chemists everywhere, it’s quite simple. You start with cold water and add heat. The cold water warms up until it hits 100°C (assuming we’re at sea level, which we are here in Ideal Land). From there, every bit of heat that is put into the system goes into vaporizing the liquid. In other words, as long as your perfect system is boiling, the temperature will be pegged at exactly 100°C and not move a whisker. Increasing the heat input merely changes how fast the change from liquid to vapor will happen - bigger, faster bubbles - but does not change the temperature. Any variation from this ideal that may be caused by vulgar reality is of no further interest to the academic. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [September 24, 2015, 9:07pm UTC](https://boards.straightdope.com/t/how-do-the-number-size-and-rate-of-steam-bubbles-relate-to-a-pot-of-waters-heat/732425/3 "2015-09-24T21:07:42Z")
OK. So it is heat-to-bubbles I’m interested in. A smiling poach and a rolling boil are differing two physical states, no? Because it is not just the violence of the bubbles physically impacting the food that is the issue I’m talking about. ---
**Author:** ![am77494](https://avatars.discourse-cdn.com/v4/letter/a/d2c977/32.png) [@am77494](https://boards.straightdope.com/u/am77494)\ **Post date:** [September 24, 2015, 10:53pm UTC](https://boards.straightdope.com/t/how-do-the-number-size-and-rate-of-steam-bubbles-relate-to-a-pot-of-waters-heat/732425/4 "2015-09-24T22:53:29Z")
I am not sure of Chemists / Physicists but Chemical Engineers typically learn to calculate bubble diameter (nucleate boiling) in heat transfer / mass transfer courses. Here is a link to calculating bubble diameters - [http://wins.engr.wisc.edu/teaching/mpfBook/node28.html](http://wins.engr.wisc.edu/teaching/mpfBook/node28.html). Equation 5.18 gives you the correlation you are looking for. Also note that there are a lot of factors involved like the surface roughness, surface tension, etc. and the correlation gives some statistical average size. This question comes into play a lot of times from food (Milk evaporation for powder milk), Power generation (Nuclear reactors - boiling liquid types, Industrial boilers, etc.), Environmental (Sea water desalination by evaporators, Hazardous waste evaporators) etc. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [September 25, 2015, 12:34am UTC](https://boards.straightdope.com/t/how-do-the-number-size-and-rate-of-steam-bubbles-relate-to-a-pot-of-waters-heat/732425/5 "2015-09-25T00:34:52Z")
> [@am77494](#): > > I am not sure of Chemists / Physicists but Chemical Engineers typically learn to calculate bubble diameter (nucleate boiling) in heat transfer / mass transfer courses. > > Here is a link to calculating bubble diameters - [http://wins.engr.wisc.edu/teaching/mpfBook/node28.html](http://wins.engr.wisc.edu/teaching/mpfBook/node28.html). Equation 5.18 gives you the correlation you are looking for. > > Also note that there are a lot of factors involved like the surface roughness, surface tension, etc. and the correlation gives some statistical average size. > > This question comes into play a lot of times from food (Milk evaporation for powder milk), Power generation (Nuclear reactors - boiling liquid types, Industrial boilers, etc.), Environmental (Sea water desalination by evaporators, Hazardous waste evaporators) etc. I say: wow. :smack: _Of course_ engineers think of this. (And I used to work for ASME…). This is way the f over my head. I don’t even know where to begin. ---
**Author:** ![Isilder](https://avatars.discourse-cdn.com/v4/letter/i/cc9497/32.png) [@Isilder](https://boards.straightdope.com/u/Isilder)\ **Post date:** [September 26, 2015, 12:37pm UTC](https://boards.straightdope.com/t/how-do-the-number-size-and-rate-of-steam-bubbles-relate-to-a-pot-of-waters-heat/732425/6 "2015-09-26T12:37:11Z")
> [@Leo\_Bloom](#): > > I say: wow. :smack: _Of course_ engineers think of this. (And I used to work for ASME…). Its actually the pressure being used as index to bubble size… It seems a bit irrelevant, as the pressure in home cooking isn’t changing… In such a small pot of water the rate of steam produced is set by the power… It takes n KW to convert m grams of boiling point water to steam per second… ---
**Author:** ![Toxylon](https://avatars.discourse-cdn.com/v4/letter/t/f05b48/32.png) [@Toxylon](https://boards.straightdope.com/u/Toxylon)\ **Post date:** [September 28, 2015, 8:47am UTC](https://boards.straightdope.com/t/how-do-the-number-size-and-rate-of-steam-bubbles-relate-to-a-pot-of-waters-heat/732425/7 "2015-09-28T08:47:52Z")
In tea-brewing circles, bubble size is linked to various water temperatures, based on a traditional Chinese system, as any number of sites shows. It’d be cool to rig up a test to see if and how well it holds when pots, water, heat sources etc. vary. [http://www.goldenmoontea.com/library/the-5-different-stages-of-boiling-water-and-how-the-chinese-use-them-for-tea/](http://www.goldenmoontea.com/library/the-5-different-stages-of-boiling-water-and-how-the-chinese-use-them-for-tea/) ---
**Author:** ![bob\_2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bob_2/32/3341_2.png) [@bob\_2](https://boards.straightdope.com/u/bob_2)\ **Post date:** [September 28, 2015, 9:52am UTC](https://boards.straightdope.com/t/how-do-the-number-size-and-rate-of-steam-bubbles-relate-to-a-pot-of-waters-heat/732425/8 "2015-09-28T09:52:06Z")
I was taught that “A stew smiles and never boils”. I am well aware that the ‘average’ temperature will be 100C but of course my kitchen is not a laboratory and local areas may well be higher, especially in a viscous mixture like a stew. Raising it to boiling point and then applying just enough to keep it there, will ensure even cooking as the mixture has time to circulate by convection. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [September 28, 2015, 3:52pm UTC](https://boards.straightdope.com/t/how-do-the-number-size-and-rate-of-steam-bubbles-relate-to-a-pot-of-waters-heat/732425/9 "2015-09-28T15:52:26Z")
> [@bob\_2](#): > > I was taught that “A stew smiles and never boils”. I am well aware that the ‘average’ temperature will be 100C but of course my kitchen is not a laboratory and local areas may well be higher, especially in a viscous mixture like a > > Raising it to boiling point and then applying just enough to keep it there, will ensure even cooking as the mixture has time to circulate by convection. “Viscous areas” speaks to the heat permeability (thta’s not the right word, I’m sure) of different heating materials: eg water poach vs. a poach in oils/butter (much lower temperature), all of which must be evaluated based on food temperature rise rates and stability times, all of which have different effects depending on the application. The modernist/molecular cooking guys have numbers up the wazoo on this. But I just wanna look at bubbles. (And listen to them, as cooks do for similar quick checks of temperature.) ---
**Author:** ![octopus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/octopus/32/3716_2.png) [@octopus](https://boards.straightdope.com/u/octopus)\ **Post date:** [September 28, 2015, 8:41pm UTC](https://boards.straightdope.com/t/how-do-the-number-size-and-rate-of-steam-bubbles-relate-to-a-pot-of-waters-heat/732425/10 "2015-09-28T20:41:14Z")
> [@Leo\_Bloom](#): > > OK. So it is heat-to-bubbles I’m interested in. > > A smiling poach and a rolling boil are differing two physical states, no? > > Because it is not just the violence of the bubbles physically impacting the food that is the issue I’m talking about. If bubbles are forming it’s boiling. So basically same physical state. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [September 28, 2015, 9:27pm UTC](https://boards.straightdope.com/t/how-do-the-number-size-and-rate-of-steam-bubbles-relate-to-a-pot-of-waters-heat/732425/11 "2015-09-28T21:27:44Z")
> [@octopus](#): > > If bubbles are forming it’s boiling. So basically same physical state. Are you saying that a one-bubble a second pot of hot water and a furiously bubbling pot of water have the same heat? ---
**Author:** ![Smeghead](https://avatars.discourse-cdn.com/v4/letter/s/f1d935/32.png) [@Smeghead](https://boards.straightdope.com/u/Smeghead)\ **Post date:** [September 28, 2015, 10:22pm UTC](https://boards.straightdope.com/t/how-do-the-number-size-and-rate-of-steam-bubbles-relate-to-a-pot-of-waters-heat/732425/12 "2015-09-28T22:22:34Z")
> [@Leo\_Bloom](#): > > Are you saying that a one-bubble a second pot of hot water and a furiously bubbling pot of water have the same heat? “Heat” is the wrong word. They should be the same temperature (ignoring minor inconvenient details about reality), and if the amount of water is identical, there will therefore be the same amount of heat energy in the pot. However, the faster-boiling pot will have more heat flow - heat is going into the system and going out as steam at a faster rate. ---
**Author:** ![octopus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/octopus/32/3716_2.png) [@octopus](https://boards.straightdope.com/u/octopus)\ **Post date:** [September 29, 2015, 2:07am UTC](https://boards.straightdope.com/t/how-do-the-number-size-and-rate-of-steam-bubbles-relate-to-a-pot-of-waters-heat/732425/13 "2015-09-29T02:07:54Z")
> [@Leo\_Bloom](#): > > Are you saying that a one-bubble a second pot of hot water and a furiously bubbling pot of water have the same heat? Heat? No. Temperature basically yes. The heat flow is higher in the furiously boiling pot but the water in a non-pressurized container has a boiling point and when it’s boiling that’s basically the temperature of the water. Will something cook faster in boiling water if you increase the boiling rate? Stuff like potatoes and carrots, I’d say no. Stuff that increases the boiling point as the water boils off, yeah.