Why does the popcorn bag restrict when I take it out of the microwave? Like the air was sucked out of it Does this happen to anyone else?

CB

Basic physics - hot air expands and cooling air contracts.

p

It is probably because the steam is escaping.

Janet

The hot air escapes, so it is like letting some of the air out of a balloon.

ckngbbbls

the popcorn bad didn't have much air in it to start with and the popping corn replaced that so the air was pushed out of the bag.

The Lord Humungus.

Boyle's law