The Food Lab: Better Home Cooking Through Science

of food—or liquid—at a stable temperature: the beer cooler.
Here’s how it works: A beer cooler can keep things cool
because it is a two-walled plastic chamber with air space
between the walls. The air space acts as an insulator,
preventing thermal energy from the outside from reaching
the cold food on the inside. Of course, insulators work both
ways—the cooler is just as good at keeping thermal energy
on the inside from escaping to the outside. Once you realize
that a beer cooler is just as good at keeping hot things hot as
it is at keeping cold things cold, the rest is easy: Fill your
cooler with water just a couple degrees higher than the
temperature you’d like to cook your food at (to account for
temperature loss when you add the cold food), seal your
food in a zipper-lock freezer bag, drop it in, and close your
cooler. Leave the food there until it is cooked. It’s as simple
as that.