In researching our post on re-popping unpopped popcorn, we learned that Harold McGee in On Food and Cooking recommends leaving the lid on your pan slightly ajar while making popcorn. This is so water vapor can escape. Otherwise, he says the crunchy popped corn will re-absorb the moisture, becoming tough and chewy instead of light and fluffy.
This makes sense to us, but we're not entirely sure how to go about leaving the lid "slightly ajar" while we're shaking it around. The potential for the lid to slip and popcorn to fly all over our kitchen seems rather high. Some experimentation will be required.
Have you ever tried leaving the lid a bit ajar? Do you notice a difference?