# pots and pans and lids **URL:** \ **Category:** Factual Questions\ **Created:** [December 15, 2000, 1:45am UTC](https://boards.straightdope.com/t/pots-and-pans-and-lids/45663 "2000-12-15T01:45:37Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![jb\_farley](https://avatars.discourse-cdn.com/v4/letter/j/9d8465/32.png) [@jb\_farley](https://boards.straightdope.com/u/jb_farley)\ **Post date:** [December 15, 2000, 1:45am UTC](https://boards.straightdope.com/t/pots-and-pans-and-lids/45663/1 "2000-12-15T01:45:37Z")
WTF?!? I boil some water for mac and cheese, put the mac an cheese in (sorry, sorry- it’s Kraft “Cheese and Macaroni”) and cover with a lid. Suds and bubbles fill the pot and boild over. As soon as I remove the lid, the foam subsides. WTF?!? jb ---
**Author:** ![capybara](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/capybara/32/202_2.png) [@capybara](https://boards.straightdope.com/u/capybara)\ **Post date:** [December 15, 2000, 2:24am UTC](https://boards.straightdope.com/t/pots-and-pans-and-lids/45663/2 "2000-12-15T02:24:53Z")
When the lid is off it boils less so there are less suds. . . or the steam has somewhere better to go. Some one will pop in and talk about heat, pressure and Boyle’s Law soon, I expect (having the lid on increases the pressure so temp is higher, I believe). ---
**Author:** ![jb\_farley](https://avatars.discourse-cdn.com/v4/letter/j/9d8465/32.png) [@jb\_farley](https://boards.straightdope.com/u/jb_farley)\ **Post date:** [December 15, 2000, 3:42am UTC](https://boards.straightdope.com/t/pots-and-pans-and-lids/45663/3 "2000-12-15T03:42:19Z")
see, I thought about that though, and I don’t buy it. If there was that great a pressure build-up, the lid woulda popped up crazy like and I’d be covered in cheap macaroni. As for the “more steam= more bubbles”, this is a huge bubble difference I’m talking about. If more steam were realy causing that much sudsing, wouldn’t a full (uncovered) boil cause my pot to overfloweth? jb ---
**Author:** ![Skelji](https://avatars.discourse-cdn.com/v4/letter/s/b38774/32.png) [@Skelji](https://boards.straightdope.com/u/Skelji)\ **Post date:** [December 15, 2000, 4:37am UTC](https://boards.straightdope.com/t/pots-and-pans-and-lids/45663/4 "2000-12-15T04:37:38Z")
Unless you make your Cheesy Macs in a pressure cooker, you won’t have that problem. The lid on a normal pot retains enough steam and heat to cause everything to boil over, but the lid has a loose enough fit to allow excess pressure to be relieved. ---
**Author:** ![jb\_farley](https://avatars.discourse-cdn.com/v4/letter/j/9d8465/32.png) [@jb\_farley](https://boards.straightdope.com/u/jb_farley)\ **Post date:** [December 15, 2000, 6:00am UTC](https://boards.straightdope.com/t/pots-and-pans-and-lids/45663/5 "2000-12-15T06:00:36Z")
Okay, but what “cause[s] everything to boil over”? still waiting, jb ---
**Author:** ![Gaspode](https://avatars.discourse-cdn.com/v4/letter/g/aeb1de/32.png) [@Gaspode](https://boards.straightdope.com/u/Gaspode)\ **Post date:** [December 15, 2000, 7:19am UTC](https://boards.straightdope.com/t/pots-and-pans-and-lids/45663/6 "2000-12-15T07:19:54Z")
I think it’s higher temperature mostly, with maybe a little bit of pressure influence. Once you remove the lid the steam can evaporate, taking all the hottests water molecules away from the mix and so cooling it. With the lid on the heated water molecules are simply evaporating and bouncing straight back into the water, carrying their heat back in with them. the pot can’t cool. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [December 15, 2000, 7:29am UTC](https://boards.straightdope.com/t/pots-and-pans-and-lids/45663/7 "2000-12-15T07:29:01Z")
Bubbles last longer in a more humid environment. With the lid on the atmosphere over the pot is at least saturated and probably supersaturated with water vapor. Rather than losing water to the atmosphere, or by it moving to the bottom of the bubble and down to the next bubble in the heap,the bubbles are probably gaining water from the atmosphere. When you take the lid off the excess water vapor wafts away into the room and you start to have liquid evaporate from the surface of the bubbles themselves. This causes the bubbles to pop. ---
**Author:** ![jb\_farley](https://avatars.discourse-cdn.com/v4/letter/j/9d8465/32.png) [@jb\_farley](https://boards.straightdope.com/u/jb_farley)\ **Post date:** [December 15, 2000, 7:37am UTC](https://boards.straightdope.com/t/pots-and-pans-and-lids/45663/8 "2000-12-15T07:37:34Z")
ahh, that makes sense **Squink**. Any corroboration? tanka, jb ---
**Author:** ![Duck\_Duck\_Goose](https://avatars.discourse-cdn.com/v4/letter/d/50afbb/32.png) [@Duck\_Duck\_Goose](https://boards.straightdope.com/u/Duck_Duck_Goose)\ **Post date:** [December 15, 2000, 2:56pm UTC](https://boards.straightdope.com/t/pots-and-pans-and-lids/45663/9 "2000-12-15T14:56:21Z")
Will Julia Child do? On one of her cooking shows, years ago, she demonstrated how to get your water JUST at the boiling point for poaching _quenelles Lyonnais_. She put a lid on the pot, and it came up to boiling. She took the lid off, and it stopped boiling. Thank you, **Gaspode,** for scientifically confirming what Aunt Julia done tole me. 🙂 ---
**Author:** ![Ivar](https://avatars.discourse-cdn.com/v4/letter/i/51bf81/32.png) [@Ivar](https://boards.straightdope.com/u/Ivar)\ **Post date:** [December 15, 2000, 4:10pm UTC](https://boards.straightdope.com/t/pots-and-pans-and-lids/45663/10 "2000-12-15T16:10:18Z")
Add a drop or 2 of vegetable oil (canola or olive). It’ll take care of the bubbles.