I always cook pasta with the lid of the pot open, because otherwise foam starts to build up and eventually boils over, maikng a huge mess. I would prefer to keep the lid on for energy saving purposes. Is this possible at all? What makes the foam build up, why does it not when the lid is open?

6 Answers 6


Use the pasta cooking techniques in this answer: Pasta: is simmering equivalent to roiling boil?

Bring just enough water to cover the pasta to a boil, put the lid on and let it sit.

Use less water, less energy, and it can't boil over if it's not boiling.

  • 2
    Like Mies said: "Less is more". Commented Oct 21, 2010 at 23:45
  • "Bring just enough water to cover the pasta to a boil, put the lid on and let it sit." Doesn't that take long to get to a boil? Commented Dec 8, 2021 at 1:07

You can use a larger pot. I always use my 12 qt stock pot to boil pasta in. I fill it anywhere from 1/3 to 2/3 full and have no problems with boil over. I too always use it with the lid on. Granted, you're going to use more energy to heat a larger quantity of water, but meh. I'd bet that your refrigerator and A/C use gobs more energy than your range.

As to why it happens? I'm speculating here, but maybe it's the back pressure on the foam bubbles when the lid is on. With the lid off the bubbles can expand rapidly, and break. With the lid on, there is slight back pressure which could restrict the bubbles ability to expand as quickly.

  • It might be currents rather than pressure - the lid could prevent a rising current from helping carry anything away? That would keep the air right above the bubbles hotter and more saturated with water vapor.
    – Cascabel
    Commented Oct 21, 2010 at 17:57
  • +1 Absolutely true, a larger pot expecially with a larger diameter does the trick.
    – pygabriel
    Commented Oct 21, 2010 at 18:16
  • 1
    A/C does use more energy than the range but whatever you pay for the range you will pay double for the A/C to pull it back out of the air. Commented Oct 21, 2010 at 18:27
  • @Jefromi: Yes, it's probably a bit of both.
    – hobodave
    Commented Oct 21, 2010 at 19:12
  • @Jefromi - We just covered this in my chemistry class. Leaving the lid on increases vapor pressure in a closed system. This is similar to how a pressure cooker works. Leave the lid off and the boiling water stays at the same temperature. Keep it on and the water gets hotter.
    – ssakl
    Commented Oct 22, 2010 at 21:58

Once the water reaches a boil and you've added the pasta you can also turn down the heat on the burner; this should reduce the creation of foam. I do not have the problem, though I also add salt and olive oil to the water and typically do not have foam.

  • I remember another answer on this site explaining why salt or oil is added, not to change the boiling point or keep the pasta from sticking, but to solve the foaming issue - but I can't find the link right now. Just wanted to semi-back up your claim with some anecdotal evidence...will comment again with the link if I can dig it up. :) Commented Oct 21, 2010 at 20:03

You can use a boil over preventer, also known as a milk watcher, among other things. It's a disk with a raised edge and a notch at one side, which you place at the bottom of the pot. It works by collecting a lot of the bubbles from the bottom underneath, enclosed by the raised edge, and releasing them as fewer, larger bubbles through the notch, so that they don't cause the foam that leads to boiling over.

Original post:

Cooking pasta without boiling over is very simple if you have a simple little piece of "pottery" called "Boil Master". I bought this in a shop somewhere when we were traveling. It is approx. 2" in Dia. and Approx. 1/2" thick. The little card that came with it said it was called "Boil Master" and was made in New Mexico by Mountain High Pottery. I have not been able to find the company or the product. It works like magic every time. It has never boiled over and I have used it for years.

  • 1
    Could you include a more detailed description, or better yet, a picture? Without that, it's not really much of an answer; the dimensions along with a name no one else uses and a local pottery shop with no online presence don't really let anyone else know what to look for.
    – Cascabel
    Commented Feb 26, 2013 at 21:22
  • Thanks for the suggestion, David - I figured out what this is usually called, and edited a helpful description into your post.
    – Cascabel
    Commented Feb 27, 2013 at 0:17

you can use a lid with holes in it - i use it for cooking and it works pretty good


If the only reason you put the lid on your cooker is to save energy, then I'd recommend just not putting the lid on. You're not "saving" anything. Your burner will be running the entire time you are cooking, lid on or off. Furthermore, regardless of whether the lid is on or off, you will be cooking your pasta at the same temperature -- 100 deg (C).

  • Of course, removing the lid does not reduce energy usage, but I don't need to have the burner on (or have it on lower heat) if the pot doesn't cool off too quickly, and the lid might help with that. For my specific case of cooking pasta, however, this has been rendered irrelevant by Sobachatina's post pointing me at the cooking instructions where you just turn the heat off completely after bringing the water to the boil. Commented Oct 25, 2010 at 14:19

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