How Popcorn Pops

Some flint and dent varieties of corn will explode and form a crisp puff, but expand far less than true popping varieties, which are generally smaller and contain a greater proportion of hard translucent endosperm. Thanks to a denser arrangement of cellulose fibers, the popcorn hull (pericarp) conducts heat several times faster than the hull of ordinary corn; and thanks to both its density and greater thickness, it is several times stronger: so the hull transmits heat more rapidly to the endosperm, and can withstand higher steam pressure from within before giving way.