How does popcorn pop? This month on Kitchen Geekery, Dr. J. explains the science of popcorn and gives us some tips on how to make your own microwave popcorn! (because it's entirely possible that she's not the only popcorn addict around FBC headquarters...

Kitchen Geekery - Why Does Popcorn Pop | Food Bloggers of Canada

If you know me, even just a little bit, you are most likely aware that I am completely addicted to popcorn. I am addicted in an "I-own-several-popcorn-makers" kind of way. One of the reasons I have a microwave is to make popcorn, but more importantly, I must be able to quickly melt butter for popcorn because popcorn without butter is a criminal offence in my world.

I bet I’m not the only one addicted to popcorn (yes, I’m looking at you), but did you know there’s a science to the popping of popcorn?

Why does popcorn pop?

Corn kernels consist of a shell (also known as the hull, the annoying part that inevitably gets stuck in your teeth in a hard to reach place) and a starchy interior. Regardless of the heat source (whether hot air, hot oil, or microwave ovens), as popcorn kernels heat up, the starchy interior releases steam.

The beauty of the popcorn kernel is that its hard shell is great at conducting heat and it is much stronger than the shell of other corn kernels. The shell of popcorn kernels can transfer heat to the starchy interior of the kernel really well causing lots of steam to form inside, and the shell traps that steam, causing a pressure buildup within the kernel. The more you heat the popcorn kernel, the more the steam builds up inside, softening the starchy interior, until the pressure inside the kernel is so great that the shell tears, causing the kernel to literally pop open!

The soft starchy interior explodes through the shell. It puffs as the steam is released, and then dries, crisps up, and cools as the steam evaporates off. The key to making crisp popcorn is to vent off the steam as the corn pops. Some stove-top methods recommend leaving the pan lid open just a crack, while certain microwave popcorn bags have small slits cut in the side for venting.

What's so special about commercial microwave popcorn bags?

You can make popcorn in a microwave with any old plain paper bag (which is what I do), but the temperature inside the bag doesn’t go up high enough to pop all the popcorn kernels in the bag, leaving behind those pesky un-popped kernels that are most upsetting to us popcorn addicts!

Microwave popcorn makers solved this problem by lining the interiors of the bag with a film that absorbs the microwaves and better conducts and transfers the heat, allowing the popcorn to hit much higher temperatures and pop faster, without scorching, achieving a much better ratio of popped to un-popped kernels. Smart and much appreciated!

Kitchen Geekery - The Science of Popcorn | Food Bloggers of Canada

What about butter flavours in commercial popcorn: are they safe?

A man in the US was awarded a pretty hefty settlement in 2012 after he developed “popcorn lung” that he said was a result of his consuming large amounts of butter-flavoured microwave popcorn on a daily basis for the better part of a decade.

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The butter flavouring was made from diacetyl, which has since been replaced with 2,3-pentanedione. To be fair, you’d have to inhale a lot of diacetyl to develop “popcorn lung”, a disease that has mainly been associated with artificial butter flavour plant workers who come into contact with (and inhale) high doses of the stuff all day long. There’s nothing wrong with consuming a little butter-flavoured microwave popcorn. Just resist the urge to stick your face in the steaming bag of butter-flavoured microwave popcorn and avoid deeply inhaling the butter flavour on a daily basis for 10 years straight. I think that’s common sense, really.

The way I make popcorn these days

To be honest, I’ve grown pretty lazy when it comes to popcorn making. I want my popcorn fast and I don’t want to have to expend too much energy, standing over a stove, worrying that I might burn it. The microwave is my latest popcorn-popping method of choice, and all you need is a paper bag.

How to make popcorn in the microwave with just a simple paper bag
Serves: 5 cups
  • ¼ cup (~ 45 grams) popcorn kernels
  • 1 paper bag
  • Salt, butter, and other seasonings
  1. Place the popcorn kernels in the paper bag, and fold over the top several times to seal it, leaving some room for popcorn popping and expansion.
  2. Put the closed bag in the centre of the microwave, and set it to heat on high for 4 minutes. The popcorn won’t take the full time so you should listen carefully to the popping (usually mine takes about 2 min 15 sec to pop most of the kernels without burning).
  3. Remove the bag from the microwave and carefully unfold the top. Watch out for the steam! It burns!
  4. Pour the popped popcorn into a big bowl and top with a generous sprinkling of salt, seasoning, and lots of melted butter. Sometimes I add Frank’s Red hot to the butter, which makes the popcorn taste like spicy chicken wings, or I make chili-lime popcorn (you can find the recipe on my blog).
  5. Enjoy!

After all this chit-chat about popcorn, I think we've all earned a bowl (or two).

Do you have a great popcorn topping recipe to share?  Leave a link to it in the comments - this bunch of FBC popcorn addicts are always looking for a new popcorn recipe!

Kitchen Geekery is written by Janice Lawandi. Janice is a PhD-chemist-turned-baker, which is why she loves to use science to understand and solve problems in the kitchen. She is currently working as a recipe tester and writer in Montreal, QC. Visit Janice’s blog, The Bake School, for more baking science and inspiration. You can also follow her on Facebook and Instagram.

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Shareba Abdul

I remember reading about that “popcorn lung” case. What an odd habit to have! I do love microwave popcorn though. I used the brown bag method for a long time, but now I have a cute Nordicware microwave popcorn bowl that I love 😀

Janice @Kitchen Heals Soul

Can you imagine the amount of salt he was probably ingesting every day from his popcorn habit too? Yikes!
I’m going to go check out that Nordicware microwave popcorn bowl now because the 3 popcorn makers I have aren’t enough 😉


I’m a big fan of the stovetop method. I learned how to do it from Simply Recipes. I have a tip to add to the stovetop method though – have the lid shifted a crack so the steam can escape a bit as the popcorn pops. When I forget to do that the popcorn is small but when I remember I get a nice fluffy pot of popcorn.

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