Reader Rick wants to know why air bubbles make crêpes rigid. Rick, it’s as easy as this: think about an air mattress when it’s full of air. You might be able to fold it, but you can’t roll it. That is until you let all the air out…then it rolls up with ease. The tens of thousands of little bubbles in a freshly-mixed crêpe batter likewise tend to “puff up” a crêpe when it cooks. That makes it fluffy, resistant to rolling and prone to cracking.