Scientists explain why food always sticks to your stupid nonstick skillet

An investigation into how oils behave on hot, flat surfaces revealed the process responsible for food sticking to non-stick pans.

Love the opening line of this new paper, published today in Physics of Fluids: “Here, the phenomenon of food sticking during frying in a pan is explained experimentally.”

Concise and straightforward, as the explanation goes: “thermocapillary convection,” according to the authors, Alexander Fedorchenko and Jan Hruby, both of the Czech Academy of Sciences.

It is very powerful knowledge. The next time this happens during cooking, you can shake your angry fist on the stove and say, “Damn, thermocapillary convection!” It will be a very fulfilling time, not only because you have a fancy new term available to you, but also because you will be fully aware of what it really means.

For their experiment, Fedorchenko and Hruby, specialists in fluid dynamics and thermophysics, tested two non-stick frying pans, one coated with ceramic particles and the other coated with Teflon. The surfaces of the pans were coated with a thin layer of sunflower oil, and then, using a hanging camera, the scientists measured how quickly it took dry spots to form and grow when the pans were heated.

Scientists noticed that as the pans were heated from below, a temperature gradient appeared through the oily film. This in turn created a surface tension gradient, which directed the oils away from the center of the pan and out to the periphery; liquids with high surface tension pull more strongly on surrounding liquids than liquids with low surface tension.

This is a prime example of thermocapillary convection at work – a phenomenon in which a gradient in surface tension forces a liquid (in this case, oil) to migrate outward. Once that happens, the food is more likely to stick to the center of the pan, a result of “a dry spot forming in the thin film of sunflower oil,” according to the study.

Fedorchenko and Hruby actually created a formula to calculate the “dewetting rate,” which measures the rate at which oil droplets recede. Very cool, but the word “dewetting” is something we don’t need in our lives right now. Scientists have also identified the conditions that lead to dry areas, resulting in the following advice:

“To avoid the formation of unwanted dry spots, the following measures (and / or) should be applied: increasing the thickness of the oil film, moderate heating, complete moistening of the surface of the pan with oil, using a heavy-bottomed saucepan, stirring food regularly while cooking, ”the authors write.

Sensational. I don’t know about you, but to me these are all extremely obvious tips (not to mention the first and third items on this list are basically the same). Except for using heavy-bottomed pans – I didn’t know that. But to be honest, I often used a cast iron pan to fry food, so I must have subconsciously felt that to be true.

Anyway, this is all making me very hungry, so I’m going to end it here, head to the kitchen and do my best to master the peculiarities of thermocapillary convection.