Scientists have discovered why razor blades become blunt after repeated use. They did research on why blades lose their sharpness. Razors are 50 times harder than hair. Even though hair is 50 times softer than the metal of a razor, the hair damages the edge of the blade. Razor blades are made from stainless steel and coated with tough materials like carbon. The scientists said each time a blade cuts a hair, the hair causes tiny amounts of damage. A blade can cut thousands of hairs. This means the life of a razor blade is limited. It needs to be replaced regularly.
The researchers used microscopes to look at how hair damages razor blades. They got a close-up view of what happens when the blade cuts a hair. One cause of damage is because a hair can make a tiny chip on the edge of a blade. This chip gets bigger as it cuts more hair. After more shaving, the blade loses its ability to cut cleanly. A researcher said he wanted to make metal stronger. He said it was interesting that, "if you cut something very soft, like human hair, with something very hard, like steel, the hard material would fail." He called this "an important engineering problem".