Although there are always some studs that just won't pop no matter what, the main reason for unpopped kernels is that they have gone too dry. To make all the kernels pop, soak them in water for about 20 minutes, then drain the water and pop as usual. The extra moisture helps produce bigger and fluffier flakes. Or, you can also use this method. Put the kernel in a mansion jar. Add one tablespoon of water and give the jar a good shake. Place the lid back on and leave it overnight.