Getting the Most from Your Microwave

By Cook's Illustrated Published March 2013

Microwave cooking is unlike any other cooking method in the kitchen. It can seem at once to be the fastest method and the most uneven. To illustrate the difference between microwave cooking and simmering, we ran the following experiment.


We microwaved a potato on a plate for 3 minutes, sliced it in half, and compared it with a potato that we simmered in water for 3 minutes.


The microwave cooked a large portion of the potato in just 3 minutes, but the heat penetration was very uneven. In contrast, the simmered potato featured a thin, consistent line of cooked potato around the perimeter.


The electromagnetic waves produced by a microwave oven create an electric field that reverses direction 4.9 billion times per second. Water molecules are polar, meaning that they contain a partial positive and a partial negative electrical charge. In the presence of the oscillating electric field, the water molecules in the potato (or any food) change direction at the same incredibly fast rate. This rapid reversal causes the water molecules to bump into one another, effectively increasing their temperature. The problem is that microwaves can’t penetrate more than an inch into food (the heat continues to move toward the center via conduction, just as it does in food cooked in an oven). What’s more, microwaves hit foods in an unpredictable pattern, so some parts will cook faster than others. Microwave ovens use turntables to help even out cooking to some degree, but only on one axis. To ensure even cooking:

1. Stir or flip food often.

2. Add a cover to trap steam that can provide another form of cooking.

3. Rest foods for a few minutes after cooking to allow hot and cool spots to even out (especially important for foods that can’t be stirred).

SIMMERED: A 3-minute simmer in hot water begins to evenly cook a potato from the outside in.

MICROWAVED: The microwave cooks a potato unevenly, making covering, flipping, and stirring during cooking crucial.