How Popcorn Pops

There are four elements involved that make popcorn "pop":
    1. Moisture inside the popcorn kernel
    2. Starch inside the kernel
    3. Hull – hard shell surrounding the kernel
    4. Heat – required temperature is 356°F

A Steam-Powered Explosion

To adequately pop the kernel, a temperature of 356° F is needed. As popcorn kernels are heated, the moisture trapped inside the hard hull turns into steam. This steam also makes the starch softer and more pliable, becoming more gelatinous. Because the steam vapors build quickly, they create "pressurized steam".

When the pressure inside the shell gets high enough (135 psi) , the hull pops open. At this point, the natural starch and protein inside the kernel quickly expand into microfine bubbles, which fuse together into a foam that cools very fast - setting the shape of the familiar popcorn puff.


Why Some Popcorn Kernels Don't Pop

Popcorn kernels that remain unpopped after cooking are often called "old maids" or "duds". Some people enjoy eating these unpopped kernels. Other people just wonder why they didn't pop.

With a better understanding of How Popcorn Pops, you'll discover the best tips to ensure that most of your kernels get popped. Start here by taking a closer look why some popcorn kernels don't pop.

Common Reasons Popcorn Doesn't Pop

    If the hull (outer shell) is punctured or cracked, it will not pop because the steam escapes and cannot build up sufficient pressure inside the popcorn seed to burst apart.
    Not your fault.

    Each kernel is made up of about 13.5 to 14% water. Without sufficient moisture inside, the kernels cannot generate sufficient steam to build and initiate the popping explosion.
    Probably not your fault.

    The moisture content of the grain is very important factor. Packaging and storage of popping corn must be carefully controlled, which makes it more expensive. If the kernels are stored in a warm, dry environment (or receive direct sunlight), the moisture inside the kernels will probably drop below the required moisture level - or completely dry out.
    If there's insufficient heat to pop the corn, the moisture cannot convert to steam quick enough to build sufficient pressure to burst through the hull barrier. Probably your fault.
    Go to How to Pop Popcorn

Why Don't Other Grains Pop?

If water inside the popcorn makes popcorn pop, why doesn't the water inside other grains, like rice and wheat, build up and pop when heated? The reason is because the other grains do not have an outer shell that traps the steam. Popcorn hulls are non-porous, so steam cannot pass through. The outer coverings of other grains are porous, so built-up steam passes through fairly easy and never builds up sufficient pressure.
Learn more in "A Moment of Science"




Do I Really Need Oil
to Pop Popcorn?

If using an Air Popper... "No". The other
popcorn equipment manufacturer's list using
some oil with their machines to prevent burning. This would include using oil in the stove-top method, too. So, the answer would be "Yes" for most popcorn popping methods.
To learn more about Grapeseed Oil, Sunflower Oil, and Canola Oil, see "Best Popcorn Oils"

Having trouble finding Grapeseed Oil at your grocer's? Many Popcorn Lovers buy their Grapeseed Oil online: BUY GRAPESEED OIL.

Grapeseed Oil is the BEST for Popping Popcorn