Inquiring minds want to know, and now we have an answer!
Researchers at the Czech Academy of Sciences found themselves perplexed by the 10% of cooking instances where food would stick to a non-stick pan, so they set out to find the reason. The answer is a bit wonky, but makes sense. Essentially, the pan is too hot.
Because heat lowers surface tension, a surface tension gradient followed the formation of the temperature gradient in the pan. Sunflower oil slipped away from the center of the pan, where it was hottest, and concentrated around the pan’s outer edges.
This gradient creates what’s called thermocapillary convection, researchers said. As heat flows through the middle and toward the outside of the pan, the oil film in the middle becomes stretched thin, destabilized and eventually ruptures.
Thermocapillary convection occurs within both flowing and stationary films. When the film becomes thinner than a critical value known as capillary length, the film breaks.
This deformity inhibits the performance of the nonstick film, whether flowing oil or the nonstick coating itself, and allows food to stick.
This leads to the next question, what to do about it. To get rid of the dry spots that cause over-heating and sticking, the researchers said:
“To avoid unwanted dry spots, the following set of measures should be applied: increasing the oil film thickness, moderate heating, completely wetting the surface of the pan with oil, using a pan with a thick bottom or stirring food regularly during cooking.”