How Many Times you can Shave Before a Steel Razors Become Dull

You wouldn't think there's much of a contest between soft hair or a little bit of beard stubble and a sharp steel razor – and yet, most of us know razors quickly lose their sharpness no matter how carefully you shave.

Now scientists have a much better idea why this is happening at the smallest scale.

By analysing blades at a microscopic level, a new study shows that even a single strand of hair – 50 times softer than steel – can cause a blade to chip under certain conditions. Once that chip appears, the metal is susceptible to further chipping, especially if the microstructure of the steel isn't uniform.

"Our main goal was to understand a problem that more or less everyone is aware of: why blades become useless when they interact with much softer material," says metallurgist Cem Tasan, from the Massachusetts Institute of Technology (MIT).

"We found the main ingredients of failure, which enabled us to determine a new processing path to make blades that can last longer."

Tasan and his colleagues ran a series of tests under the watchful eye of a scanning electron microscope (SEM), involving both normal facial shaving and lab experiments where the angles and cutting depths could be carefully controlled.

While very little wear was noticeable at the edges of the razors, the high-resolution imagery showed chips forming along certain parts of the razors. This happened irrespective of the thickness of the hairs being cut.

"This created another mystery: we saw chipping, but didn't see chipping everywhere, only in certain locations," says Tasan.