In 2022, the Konbini media launched a survey to put an end to a debate that divides France: are crepes eaten folded or rolled? The verdict was clear, the folded version appeals the most to our fellow citizens. And according to New Scientist, these flexible disks and their folding could teach us more about physics than we think.
If you fold a pancake, what keeps it like that? And how many times can you bend it before it rebels and returns to its original shape? These are the existential questions that Tom Marzin, a physicist from Cornell University in New York State, asked himself while on vacation in his native Brittany. Who else but a Frenchman to make crepe folding his research project? The results were presented at the American Physical Society, the world’s largest physics society.
If there is already work done on permanent type folds (like origami), Tom Marzin explains that his study is very different because it concerns smooth folds, which are a struggle “between gravity and elasticity”he says. To study how a pancake bends under its own weight, Tom Marzin fixed one side of it on a table and let the other end hang in the air, thus measuring its sag.
No more than four times
He showed that this behavior could be summarized by a single number, the “elastogravimetric” length, which combines the density of the material, its rigidity and the effect of gravity. This unique figure not only helps predict the sag of a pancake, but also helps us understand how other soft materials behave in similar situations.
To test this theory, Tom Marzin conducted various experiments with plastic discs, tortillas and, of course, pancakes. The specialist’s equations predict that a standard pancake, 26 centimeters in diameter and 0.9 millimeters thick, can be folded up to four times, while a 1.5 mm thick tortilla of the same size, which has 3.4 times greater elastogravity, will only allow two folds.
Obviously, all this explanation will have made you want to eat pancakes but unfortunately, Candlemas has already passed… This strange custom has its roots in both pagan and Christian traditions: celebration of light and the return of good weather among the Romans, religious festival of the Presentation of Jesus, with pancakes round and golden like the sun, symbolizing prosperity and luck.
Afterwards, for the sake of science, nothing stops you from cooking a few this week. Just to see if Tom Marzin is telling the truth.
