Read our COVID-19 research and news.

Your hair can crack steel when it hits the right spot

Although your hair is much softer than steel, razors typically only last for a handful of shaves. Previously, researchers attributed this to the sharp edge gradually wearing down after each use. But a new study reveals a different process at play.

Researchers used a powerful electron microscope to observe how the razor blades change after shaving. Instead of the razor slowly and evenly losing its sharp edge, they instead saw the formation of tiny cracks, then large chips of steel flaking off the edge of the blade.

By observing this cutting in action under a microscope (above) the researchers discovered the roughness of the blade’s edge made it vulnerable to splitting. Steel, although hard overall, varies in hardness throughout its microstructure. When the hair pushed on a softer region bordered by a harder region, the stress on this boundary fractured the blade, the team reports this month in Science.

Now that they understand why razor blades fail, the scientists hope to develop longer lasting alternatives. They are experimenting with using high pressure to mold steel into a sharp, even edge—and soon plan to test its durability.