Scientists have found why razor blades become blunt after use. They found out why blades lose their sharpness. Razors are 50 times harder than hair, but hair damages the edge of a blade. Razor blades are made from steel. They are toughened with carbon. Each time a blade cuts a hair, the hair damages the blade a little. A blade can cut thousands of hairs. This means the life of a razor blade is short. It needs to be replaced often.
The scientists used microscopes to get a close-up view of what happens when a blade cuts a hair. They said a hair made a small chip on the blade. This chip got bigger as it cut more hair. After more shaving, the blade could not cut cleanly. A scientist was interested that, "if you cut something very soft, like human hair, with something very hard, like steel, the hard material would fail." He said this is "an important engineering problem".