But there’s one proviso. The stretching caused by slicing arises through friction between the sideways-sliding wire and the gel surface. If there’s not enough friction, the wire can’t gain traction and some of the advantage of slicing is lost. So very smooth wires don’t cut as well as rougher ones, and the wire can’t tug so effectively either if it is pulled too fast across the gel surface. Ideally one should find a configuration in which the force required to move the blade against friction is more or less exactly equal to the force needed to initiate a crack.
It’s not just the slicing action of carving knives that the study helps us to understand. For example, a paper cutter uses a hinged or moving blade so that the cutting edge moves steadily across the paper surface rather than pressing down on it all at once. The same is true, the researchers mordantly note, of the angled blade of the French guillotine, ensuring a clean slice rather than a messy, squeezing chop. Whether or not you choose to divulge this morsel of information as the Christmas turkey is being carved is, of course, up to you.