Every parent has had to field their fair share of “kid questions”: those innocent, wide-eyed inquiries that presuppose that Mom and Dad know everything there is to know in the world and can explain it, besides. The classic “kid question,” of course, is “why is the sky blue”?
“Why does food stick to what is supposed to be a no-stick pan?” is another good example of a kid question. And depending upon a parent’s mood at the time, and whether the parent is trying to use a spatula to lift a stuck egg from a frying pan without splitting the yolk, answers might range from some quasi-scientific-sounding mumbo-jumbo that you figure will satisfy the kid and cause him or her to stop asking those infernal questions to an honest answer that will give the kid more information than they bargained for, like: “Well, Tommy, sometimes in life things don’t work like they are supposed to, and you’re just going to have to get used to it, okay?”
It’s nice when science lends beleaguered parents a hand and provides information that will allow them to answer those tough questions. Researchers at the Czech Academy of Sciences have done just that by carefully examining the no-stick pan issue and publishing their research in the Physics of Fluids journal. The scientists found that dry spots can form even on oiled, “no-stick” pans, and that’s where the food sticks. The dry spots are created by a process called thermocapillary convection, in which oil moves from the hot center of the pan to the cooler edges, and the thin coating of oil in the center of the pan becomes destabilized and eventually ruptures — leaving that dreaded dry spot that threatens to ruin your otherwise perfectly cooked egg. (And if you don’t want thermocapillary convection in your kitchen, the scientists helpfully note: “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.”).
So there you have it: thermocapillary convection is the right answer. And the great thing about that answer is that once you start talking about thermocapillary convection, capillary length, and oil destabilization, your kid will probably lose interest and stop asking those questions. It turns out they probably didn’t really want an actual answer, they just wanted to reassure themselves that Mom and Dad do know everything there is to know.
Feel free to use “thermocapillary convection” to answer other kid questions, including the “why is the sky blue” head-scratcher. It will serve until your children reach the teenage years, when the questions stop and parents suddenly become far less knowledgeable than friends.