Microwaving a cup of water before nuking the popcorn improves results? Why?

If it was just a matter of the steam helping to cook the popcorn more evenly, quickly, or thoroughly, why wouldn’t they recommend heating a cup of water before cooking anything? :dubious:

most things you might cook in the microwave have water on the surface and so the heat starts there. popcorn kernels need the center heated to boiling before the dryer outside burns.

Nobody wiling to do an experiment by microwaving the same brand once with and once without a cup of water beforehand? Where’s the adventorous spirit of the dopers? :slight_smile:

Put a bag of unpopped popcorn in the microwave, and any humidity you’ve added to the oven chamber by first heating a cup of water won’t penetrate the bag any time in the next couple of minutes.

Either way, fire up the microwave and start popping. Pop a few dozen kernels, and you’ve just released a whole lot of steam on the inside of the bag; in fairly short order the inside of the bag is at 100% relative humidity.

I’m at a loss to conceive of any way that heating a cup of water could affect the behavior of a bag of popcorn.

Here’s the brand:


They claim its for pre-heating the microwave, which seems silly. Microwaves use radiation not convection to heat things.

If I don’t heat (usually boil) a small amount of water in the microwave first, my popcorn always burns.

My machine has a ‘popcorn’ button on it, and we learned that after tossing out the first burned bag, the second bag popped dosen’t burn even if we let if finish on it’s own.
So we do the water thing.

The magnetron which creates the radiation does have a heated cathode which needs to heat up to work at full power, so it’s not completely silly. I suspect that the warm-up time on any modern microwave is measured in seconds however. Might have been more of an issue in older microwave ovens.

I considered that, because I’ll probably make a couple bags of popcorn later, but I’d need to have the microwave at “resting” temp to get an accurate comparison. Any ideas how long I should leave microwave idle between bags to achieve that?

(My kids love popcorn, and I have plenty to use for experimentation. Kids and popcorn, both.)

This isn’t true. Water does heat better than some other things that we eat, but it is by no means the only thing that a microwave will heat. You can test this easily. Put a cup of salt into the microwave. No water in there, and it will get plenty hot.

This is not true, either (although I don’t recommend testing it). I accidentally ran a microwave empty once (I meant to just use the timer), and the rotating glass dish inside got so hot that it broke from heat stress (took about 20 minutes).

any molecules that would easily get hot would then would have similarities to water such as being dipoles and have freedom of movement.

you will notice i said short times in my statement.

i was speaking in the sense of cooking which absorbs most of the energy and ordinary time frames of a minute to ten. usually if cooking needs more time than that you do it for only that long and let it rest (heat conducts through the food and cooks the whole item, if you just blast it the outside will burn before the inside cooks).

i was not speaking of abusing (even accidentally) the oven by running it empty for 20 minutes. i suppose i should have qualified my statement to the ordinary cooking use which seemed to be the topic.

Whoa. Slow down. The reason that info is on a bag of popcorn is in the event that you use an automatic “Popcorn” setting on the microwave. Those work not by establishing a set time to run and cut off, but by keying a humidistat. The Popcorn setting turns the oven off when a certain degree of humidity is detected by the sensor. Remember that popcorn pops by turning its internal moisture to steam - which escapes into the surrounding space. Obviously, heating water will increase the amount of humidity in the oven slightly, and the popcorn company has determined that some added humidity is needed in most ovens in order for the popcorn to come out correctly when it automatically shuts off. I’m guessing that many popcorn bags are sealed well enough so that the humidity produced by popping the corn doesn’t escape sufficiently to trip the humidistat - so they ask you to put a little extra in the oven so the popcorn doesn’t burn (see above post by Keweenaw).

What “heat transfer”? You’re the second person to mention this. There is no heat exchange between the microwave and the food.

Really? Is that how those work? I never would have guessed that. Interesting.