Why do I always find that some kernels just won’t pop in every batch of popcorn that I hear up? And for that matter, why does popcorn expand? Can any corn be popped?
There’s a little bit of water inside each kernel. When you heat it up, the water turns to steam and expands thereby causing a mini explosion that blows the insides out of the kernal.
Haj
And the non-popping ones are too dry, or they have leaks in the husk so the steam can’t build up. Most varieties of corn don’t have a husk that’s strong enough to hold popping pressure.