Foil is for leftovers. Paper is for crispness.

If you want a warm sandwich or quesadilla to stay crisp in a lunch box, wrap it in paper, not foil.

Foil is the problem. Hot food releases steam, and foil traps that steam against the bread. Steam condenses back into water, and you end up with a soggy, sad quesadilla. Paper — parchment, a paper towel, even a brown bag — lets that moisture escape while still holding in enough heat for a lunch box.

Also, let the thing sit on a wire rack for a couple minutes after cooking. That stops the carryover steaming that happens while it’s too hot to wrap. Then wrap it loosely in paper. For separators, parchment paper between halves or between the sandwich and anything wet (like fruit or a sauce cup) is the way. It’s breathable but still a barrier.

If you truly need lunch to be hot- hot, use a thermos or an insulated bag. Foil just keeps the sogginess in.

Crispness is a battle against steam, and paper is your ally.