The Difference Between Boiling and Simmering

Dear Home Ec 101,

I’m embarrassed to actually ask this, but what is the difference between boiling and simmering? A lot of your recipes say bring to a boil and reduce the heat to a simmer. What does that mean and why does it matter?

Signed,

Baffled Beginner

Heather says:

Basic questions like this are encouraged here. If you’re asking, I guarantee there are plenty of other people out there who don’t know either.

Do you remember high school chemistry and surface tension? Water molecules have an attraction to one another caused by the polar nature of each molecule. If you were able to see an individual water molecule it would have a bent shape, something like a V.  The point of the V is the oxygen molecule which hogs the electrons and the arms of the V would be the slightly positive hydrogen atoms. As you may remember opposites attract, the hydrogen atoms of one molecule are attracted to the negative oxygen atom of another and this creates the phenomenon of surface tension. All this means is that water molecules like to stick together and it takes energy to break them apart.

That energy is heat. At sea level water boils at 212°F, it’s a very convenient and observable benchmark when it comes to cooking. When water reaches its boiling point, which slowly drops with altitude the bubbles break the surface. Once the boiling point is reached, even if you turn up the burner, the liquid will not increase in temperature. It may boil more vigorously as more liquid turns to gas, but it won’t get any hotter.

Here’s a handy reference for those of you who don’t live at sea level:

Altitude, m Boiling point of water, °C
0 (0ft) 100 (212°F)
300 (984.25ft) 99.1 (210.3°F)
600 (1968.5ft) 98.1 (208.5°F)
1000 (3280.8ft) 96.8 (206.2°F)
2000 (6561.68ft) 93.3 (199.9°F)
4000 (13123.36ft) 87.3 (189.1°F)
6000 (19685.04ft) 81.3 (178.3°F)
8000 (26246.72ft) 75.5 (167.9°F)

Most of the time recipes will call for a liquid to be brought to a boil first, this is to compensate for the drop in temperature when food is added to the cooking liquid.

The boiling point is too hot for cooking many foods. Turn the burner down.

There are exceptions for starches and vegetables.

Simmering is the stage before the bubbles have enough energy to break the surface tension and the temperature range is from 185°F – 205°F or 85°C – 96°C. Not only does simmering require less energy from your appliance, it also keeps many proteins from becoming tough. This is why soups and stews are simmered rather than boiled, additionally the vigorous bubbling action of boiling can break apart some items like fish.

Most of the time crock pots or slow cookers are designed to cook in the simmering range, but you should test out your appliance by filling it partway with water and allowing it to reach temperature at both the high and low settings before leaving an item unattended for an extended period of time.

Not all stoves or ranges make simmering easy, in fact simmering on some gas stoves can be quite difficult, it may be necessary to move the pot so it is not centered over the flame. Be careful to ensure the pot is still balanced and won’t tip easily.

Just to throw this out there, poaching* is another way to cook with hot water and it’s temperature is even lower than simmering and it covers the range 160°F – 180°F or 72°C – 82°C.  Poaching is often reserved for delicate items like eggs and fish.

Last tidbit, sometimes menus at restaurants will refer to meat as boiled. It’s not, it’s just an inaccurate description.

*Am I the only weirdo who can be merrily writing along and brought to a standstill by a word? Poach. It’s just fun to say, which is weird since roach is just nasty. Moving along*

Send your domestic questions, no matter how basic, to helpme@home-ec101.com.

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Comments

  1. madie says

    Last night I was making one of those prepared pasta things. The directions state to boil the water & milk, and then add the pasta and continue boiling. I always lower the temperature becasue I've learned from experience that if i leave it boiling, it will boil over and make a mess. But if boiling is too hot for cooking most foods wouldn't the directions state to lower the temperature after adding the pasta?

  2. NGS says

    Wider. Whenever I see the word wider I am compelled to repeat it over and over and over again. Wider. Wider. It's a weird word. You're not alone.

  3. Judith says

    Thanks for the boiling temperature chart ………. I need to check the temperatures both on my new crockpot and on my instant read thermometer. This may motivate me.
    BTW, thanks, too, for your information on High Fructose Corn Syrup and on MSG. Thought provoking. I'm printing off the list of where MSG may be hiding, just to look at some of the food I have in my cupboards and to keep in mind as I shop. I've been an avid label reader for years but don't always know what some of the ingredients listed are.. I've finally worked my way into 85% whole foods; we use much fewer canned/boxed/frozen foods than we used to. I still fall prey to the occasional boxed cake mix or frozen pizza or can of Progresso soup, but much of what we eat is whole food.
    Thanks for all you diverse encouragement and information.

  4. Becca says

    Weehawken. I shipped a cake to Weehawken yesterday and declared this to be my favorite thing to say of the week….and shared that declaration with the people shipping my cake and all the other customers waiting in line.

    Meanwhile…..I am glad to have learned something so early in my day. I am sure I was taught this once before during my fickle teenage years but it is nice to re-learn at a stage in life when I will remember!
    My recent post Baby Shower Recipe Ideas

    • says

      It's not you, it's the flame, seriously. With electric burners there is a rheostat which throttles the electrical current regulating the temperature. With a gas stove, only the size of the flame is controlled making it more difficult to regulate an exact temperature.

    • says

      I have a gas range as well and I usually use a larger pot when I'll need to simmer so I can do it right. I'll bring to boil, and then move the pot to balance between two burners, instead of directly over one burner. It tends to work better moving the pot off the flame.

      You should see my mother-in-law cook on her WOODSTOVE! Lol!

  5. says

    Learned the hard way that pasta must BOIL — if you cook it at too low a temp, it turns out just so wrong. Gummy-ghetti, anyone? Oh, and set a time. Once I forgot it, left the room. Came back to macaroni that went right thru the colander holes when I drained it!

    RE: Word weirdness – I collect words that strike my fancy, mostly based on how they sound, but sometimes on the meaning. Favorites: Antiquity, artisanal, vernacular, defenestration, touchstone.

    • caroline says

      My SIL boils her pasta, but she does not drain it when it's done cooking, just moves it off the hot burner and then dishes it out right from the pot. It seems to me that the hot water would keep the pasta cooking and it would get overdone pretty quickly.