# Microwaving a cup of water before nuking the popcorn improves results? Why? **URL:** \ **Category:** Factual Questions\ **Created:** [August 3, 2009, 4:04am UTC](https://boards.straightdope.com/t/microwaving-a-cup-of-water-before-nuking-the-popcorn-improves-results-why/505130 "2009-08-03T04:04:21Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![stuyguy](https://avatars.discourse-cdn.com/v4/letter/s/ec9cab/32.png) [@stuyguy](https://boards.straightdope.com/u/stuyguy)\ **Post date:** [August 3, 2009, 4:04am UTC](https://boards.straightdope.com/t/microwaving-a-cup-of-water-before-nuking-the-popcorn-improves-results-why/505130/1 "2009-08-03T04:04:21Z")
The package of store brand microwaveable popcorn I just popped suggests heating a cup of water in the nuker for a minute before putting in the popcorn. Supposedly it improves the popping results. Why? Does the microwave mechanism need to “warm up” like those old TVs and radios? ---
**Author:** ![Philster](https://avatars.discourse-cdn.com/v4/letter/p/13edae/32.png) [@Philster](https://boards.straightdope.com/u/Philster)\ **Post date:** [August 3, 2009, 4:11am UTC](https://boards.straightdope.com/t/microwaving-a-cup-of-water-before-nuking-the-popcorn-improves-results-why/505130/2 "2009-08-03T04:11:22Z")
The internal parts of the microwave cooking comparment (walls, floor, door, turntable dish) won’t need to heat up when you go to heat up the popcorn, and that makes the process faster and more consistent. ---
**Author:** ![kaylasdad99](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kaylasdad99/32/3398_2.png) [@kaylasdad99](https://boards.straightdope.com/u/kaylasdad99)\ **Post date:** [August 3, 2009, 4:11am UTC](https://boards.straightdope.com/t/microwaving-a-cup-of-water-before-nuking-the-popcorn-improves-results-why/505130/3 "2009-08-03T04:11:38Z")
I never saw such a “tip” on the instructions of a bag of microwave popcorn. But I’ll certainly be watching this space. ---
**Author:** ![ivn1188](https://avatars.discourse-cdn.com/v4/letter/i/e480ec/32.png) [@ivn1188](https://boards.straightdope.com/u/ivn1188)\ **Post date:** [August 3, 2009, 4:12am UTC](https://boards.straightdope.com/t/microwaving-a-cup-of-water-before-nuking-the-popcorn-improves-results-why/505130/4 "2009-08-03T04:12:36Z")
Boiling the water makes steam, the steam/vapor remaining in the oven when you pop the popcorn is more efficient at transferring heat evenly to the popcorn, and helps temper cold spots in the microwave. ---
**Author:** ![ivn1188](https://avatars.discourse-cdn.com/v4/letter/i/e480ec/32.png) [@ivn1188](https://boards.straightdope.com/u/ivn1188)\ **Post date:** [August 3, 2009, 4:15am UTC](https://boards.straightdope.com/t/microwaving-a-cup-of-water-before-nuking-the-popcorn-improves-results-why/505130/5 "2009-08-03T04:15:05Z")
> [@Philster](#): > > The internal parts of the microwave cooking comparment (walls, floor, door, turntable dish) won’t need to heat up when you go to heat up the popcorn, and that makes the process faster and more consistent. The sides/ etc in the microwave don’t actually heat up much. There would be no need to warm the oven itself. ---
**Author:** ![stpauler](https://avatars.discourse-cdn.com/v4/letter/s/9d8465/32.png) [@stpauler](https://boards.straightdope.com/u/stpauler)\ **Post date:** [August 3, 2009, 4:21am UTC](https://boards.straightdope.com/t/microwaving-a-cup-of-water-before-nuking-the-popcorn-improves-results-why/505130/6 "2009-08-03T04:21:22Z")
I can’t believe a bag of popcorn would be [so welcoming to lawsuits.](http://www.snopes.com/science/microwave.asp) ---
**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\ **Post date:** [August 3, 2009, 4:55am UTC](https://boards.straightdope.com/t/microwaving-a-cup-of-water-before-nuking-the-popcorn-improves-results-why/505130/7 "2009-08-03T04:55:28Z")
> [@Philster](#): > > The internal parts of the microwave cooking comparment (walls, floor, door, turntable dish) won’t need to heat up when you go to heat up the popcorn, and that makes the process faster and more consistent. Those things should never heat up very much at all, except by convection, because they aren’t made of food. I vote for the steam explanation. ---
**Author:** ![iamthewalrus\_3](https://avatars.discourse-cdn.com/v4/letter/i/258eb7/32.png) [@iamthewalrus\_3](https://boards.straightdope.com/u/iamthewalrus_3)\ **Post date:** [August 3, 2009, 6:30am UTC](https://boards.straightdope.com/t/microwaving-a-cup-of-water-before-nuking-the-popcorn-improves-results-why/505130/8 "2009-08-03T06:30:12Z")
Would a minute really produce steam? I usually have to microwave a coffee cup of water for 2 minutes to heat it to steaming. 1 minute would just leave it lukewarm. ---
**Author:** ![Hampshire](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hampshire/32/4887_2.png) [@Hampshire](https://boards.straightdope.com/u/Hampshire)\ **Post date:** [August 3, 2009, 1:30pm UTC](https://boards.straightdope.com/t/microwaving-a-cup-of-water-before-nuking-the-popcorn-improves-results-why/505130/9 "2009-08-03T13:30:34Z")
Is it steam they’re wanting or just some humidity? I wonder if you’d get the same effect by just misting the inside of the microwave with a spray bottle? ---
**Author:** ![Baracus](https://avatars.discourse-cdn.com/v4/letter/b/2bfe46/32.png) [@Baracus](https://boards.straightdope.com/u/Baracus)\ **Post date:** [August 3, 2009, 1:55pm UTC](https://boards.straightdope.com/t/microwaving-a-cup-of-water-before-nuking-the-popcorn-improves-results-why/505130/10 "2009-08-03T13:55:37Z")
> [@Hampshire](#): > > Is it steam they’re wanting or just some humidity? > I wonder if you’d get the same effect by just misting the inside of the microwave with a spray bottle? Whatever they expect to the cup of water to produce in one minute of nuking, I wonder how it is supposed to affect what is happening _inside_ the bag. ---
**Author:** ![JerseyFrank](https://avatars.discourse-cdn.com/v4/letter/j/bcef8e/32.png) [@JerseyFrank](https://boards.straightdope.com/u/JerseyFrank)\ **Post date:** [August 3, 2009, 2:32pm UTC](https://boards.straightdope.com/t/microwaving-a-cup-of-water-before-nuking-the-popcorn-improves-results-why/505130/11 "2009-08-03T14:32:05Z")
> [@Baracus](#): > > Whatever they expect to the cup of water to produce in one minute of nuking, I wonder how it is supposed to affect what is happening _inside_ the bag. WAG: The presence of increased water vapor in the microwave surrounds the bag and aids in heat transfer. I’m skeptical of the effectiveness. ---
**Author:** ![AndrewL](https://avatars.discourse-cdn.com/v4/letter/a/3d9bf3/32.png) [@AndrewL](https://boards.straightdope.com/u/AndrewL)\ **Post date:** [August 3, 2009, 2:53pm UTC](https://boards.straightdope.com/t/microwaving-a-cup-of-water-before-nuking-the-popcorn-improves-results-why/505130/12 "2009-08-03T14:53:42Z")
I would expect steam in the microwave to reduce the effectiveness of heating the popcorn rather than improve it. Microwave ovens do not heat by conduction or convection. They heat by bombarding the food with microwave radiation of a frequency optimally absorbed by water. I would expect steam in the chamber to absorb some of the radiation, therefore blocking it from reaching the popcorn. Even though the oven itself doesn’t need to warm up, the cavity magnetron which generates the microwaves includes a hot cathode element which may need to be warmed up to operate consistently before making your popcorn. I think the idea that nuking water first helps to get the magnetron to operating temperature is plausible. ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [August 3, 2009, 2:57pm UTC](https://boards.straightdope.com/t/microwaving-a-cup-of-water-before-nuking-the-popcorn-improves-results-why/505130/13 "2009-08-03T14:57:18Z")
> [@JerseyFrank](#): > > WAG: The presence of increased water vapor in the microwave surrounds the bag and aids in heat transfer. > > I’m skeptical of the effectiveness. I would think the presence of more water in there would divert some of the energy and reduce the amount of heat getting to the popcorn. I base this on knowing that the more microwave-responsive stuff there is, the longer it takes to heat it up (e.g. cooking two potatoes vs. cooking one). At this point, I’m very skeptical of the effectiveness. On preview: What **AndrewL’s** first paragraph said. As to his second paragraph, I dunno. ---
**Author:** ![the\_first\_supraliminal](https://avatars.discourse-cdn.com/v4/letter/t/f475e1/32.png) [@the\_first\_supraliminal](https://boards.straightdope.com/u/the_first_supraliminal)\ **Post date:** [August 3, 2009, 3:01pm UTC](https://boards.straightdope.com/t/microwaving-a-cup-of-water-before-nuking-the-popcorn-improves-results-why/505130/14 "2009-08-03T15:01:55Z")
I think the benefit is not in speed, but in the moisture preventing burning of dry popped kernels. ---
**Author:** ![PlainJain](https://avatars.discourse-cdn.com/v4/letter/p/5daacb/32.png) [@PlainJain](https://boards.straightdope.com/u/PlainJain)\ **Post date:** [August 3, 2009, 3:02pm UTC](https://boards.straightdope.com/t/microwaving-a-cup-of-water-before-nuking-the-popcorn-improves-results-why/505130/15 "2009-08-03T15:02:18Z")
What’s the brand? I’ll call them. ---
**Author:** ![Liberal](https://avatars.discourse-cdn.com/v4/letter/l/848f3c/32.png) [@Liberal](https://boards.straightdope.com/u/Liberal)\ **Post date:** [August 3, 2009, 3:10pm UTC](https://boards.straightdope.com/t/microwaving-a-cup-of-water-before-nuking-the-popcorn-improves-results-why/505130/16 "2009-08-03T15:10:28Z")
Plus, the wattage varies on microwave ovens. Ours is only 900 watts. But it does convection cooking, broiling, and other things. It just will not pop a bag of popcorn properly. A few kernels, and then the bag starts to burn. ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [August 3, 2009, 3:16pm UTC](https://boards.straightdope.com/t/microwaving-a-cup-of-water-before-nuking-the-popcorn-improves-results-why/505130/17 "2009-08-03T15:16:32Z")
microwaves only heat water (or certain substances which have similarities). put oil in the microwave and you see that it won’t heat the same. the microwaves excites (that is the technical term) the water molecule causing it to boogie (nontechnical term) the friction of the molecule movement creates heat. the microwave frequency is tuned for just affecting the water molecule. you will notice that some containers (like glass) only get hot after long microwaving where they heat by conduction from the hot food, short times only the food is hot and not the glass, heating an empty glass will not get hot. some plastics have some of the same molecular structure in them as water and heating an empty container will come out hot (these plastics will deteriorate if used long term in the microwave, there are health issues claimed by some with some plastics in the microwave as well). metal surfaces will reflect microwaves. some popcorn poppers for use in microwave or single use packages have a metalized piece (cardboard that is coated) to reflect the microwaves close to the kernels. a piece of metal at an electrically resonant length for the microwaves will absorb the microwaves and get hot and emit microwaves with problematic possibilities inside the oven. putting water into the oven earlier makes steam. steam in the air will absorb microwaves, maybe this heats the air in the microwaves slightly. this might let the kernels get hot until they pop without burning, the water (from steam) on the kernel surface gets hot. people claim microwaves cook from the inside which is not true, the claim started because the surface didn’t sear like a thermal oven or broiler, the microwaves get absorbed by the first water they touch on the surface. the kernels would burn before popping. a kernel pops because the water on the inside boils and explodes the kernel, if the outside of the kernel gets hot enough to burn before the inside water boils then you have a burnt kernel and not a popped one. on your own nonpackaged popcorn it is important to know your kernels are hydrated. old dry kernels pop poorly. letting them soak half a day in a closed jar with a little water charges them up with water. i noticed i’ve restated some comments that were recent while i was typing, i’m a slow writer. ---
**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\ **Post date:** [August 3, 2009, 4:07pm UTC](https://boards.straightdope.com/t/microwaving-a-cup-of-water-before-nuking-the-popcorn-improves-results-why/505130/18 "2009-08-03T16:07:38Z")
> [@johnpost](#): > > microwaves only heat water (or certain substances which have similarities). put oil in the microwave and you see that it won’t heat the same. the microwaves excites (that is the technical term) the water molecule causing it to boogie (nontechnical term) the friction of the molecule movement creates heat. the microwave frequency is tuned for just affecting the water molecule. you will notice that some containers (like glass) only get hot after long microwaving where they heat by conduction from the hot food, short times only the food is hot and not the glass, heating an empty glass will not get hot. I have a granite pad that was marketed as a food warmer. You put it in the microwave and it heats up. Then you use it as a trivet and it supposedly helps keep food warm longer. Does granite have water in it? ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [August 3, 2009, 5:08pm UTC](https://boards.straightdope.com/t/microwaving-a-cup-of-water-before-nuking-the-popcorn-improves-results-why/505130/19 "2009-08-03T17:08:28Z")
It’s possible a person who believes it helps the popcorn added this to the instructions, without there being any actual benefit. ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [August 3, 2009, 5:16pm UTC](https://boards.straightdope.com/t/microwaving-a-cup-of-water-before-nuking-the-popcorn-improves-results-why/505130/20 "2009-08-03T17:16:16Z")
> [@CookingWithGas](#): > > I have a granite pad that was marketed as a food warmer. You put it in the microwave and it heats up. Then you use it as a trivet and it supposedly helps keep food warm longer. > > Does granite have water in it? i really would like to know something about rocks and minerals. one of these decades maybe i’ll learn some of it. some reasons water is affected is that it is a dipole (plus and negative charges in specific locations in the molecules) and molecular bond characteristics that allow it to get excited by those particular microwaves. molecules of other substances that are close in these properties to what water has would get similarly affected. also the water has to have some ability to move to create friction. ice is a crystal without molecular freedom, so it melts very slowly in the microwave, only until there is some liquid water to get hot does it speed up. minerals can have water in them, hydrates, but i think there wouldn’t be freedom of movement. and to what i know (which is next to nothing) granite doesn’t have hydrates in it. rocks can absorb water. there has to be pressure relief when that water would boil or the rack might fracture. so i’m ignorant on your question. [Next page](https://boards.straightdope.com/t/microwaving-a-cup-of-water-before-nuking-the-popcorn-improves-results-why/505130.md?page=2)