Conduction, convection and radiation: how heat reaches food
Beginner Kitchen science
The three ways heat moves into food: by direct contact, by moving air, water or oil, and by glowing infrared rays.
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How do you do it?
- Use the convection setting for crisp roasting, and drop the temperature about 25°F or check doneness early.
- Leave space between pieces in the pan and oven so hot air can reach every side.
- Use a broiler or grill when you want fast surface browning on thin food; that is radiant heat.
- Cut food to an even thickness; a piece twice as thick takes much more than twice as long to cook through.
Why does it work?
Conduction is heat passing through contact: burner to pan, pan to food, and the outside of the food to its center. Convection is heat carried by a moving fluid, such as boiling water, frying oil or air pushed by an oven fan. Radiation is infrared energy from glowing coals, a broiler or hot oven walls, and it browns whatever surface faces it. Water and oil carry heat far better than air, which is why you can reach briefly into a 400°F oven but never into 212°F water. Inside the food, heat moves slowly by conduction from the outside in, so thickness controls cooking time more than oven temperature does.
What are the common mistakes?
- Crowding the pan — trapped steam blocks hot air and the food steams instead of browning.
- Cranking the heat on a thick roast — the outside overcooks before the center catches up.
Still stuck? Watch someone do it on YouTube.
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