Thick lustrous hair is not stronger than thin hair, study finds

Thick lustrous hair is not stronger than thin hair, an American study has found.

The surprising findings from the research conducted by the University of California showed that thin hair is in fact stronger than thicker strands, after analysing the way it breaks.

Weak hair, which results in split ends, is often exacerbated through rough towel drying, overwashing and blow-drying wet hair.

Scientists took samples of hair from animals such as humans, horses and giraffes, using a machine to pull the strands until they tore.

Publishing their results in the scientific journal, Matter, they found that thin hair could cope with more tension than thin hair before it broke.

Using an electron microscope to analyse the tears, they found that the hair strands broke in different ways, despite most hair having a similar structure.

"We were very surprised by the result," said Dr Wen Yang, a nanoengineering researcher at the University of California, San Diego.

"Because, intuitively, we would think thick hair is stronger.

"Shearing is when small zig-zag cracks are formed within the material as a result of stress.

"These cracks then propagate, and for some biological materials, the sample isn't completely broken until the small cracks meet.

"If a material shears, it means it can withstand greater tension and thus is tougher than a material that experiences a normal fracture."

The researchers found that for animals such as boars, giraffes and elephants which have wider diameter of hair made a generally clean break.

Animals with hair with a smaller diameter such as humans and horses had more of an uneven break - indicating it can withstand greater tension.

Co-author Professor Robert Ritchie added: "The notion of thick being weaker than thin is not unusual, and we have found that happening when studying brittle materials like metal wires.

"This is actually a statistical thing, which is a bigger piece will have a greater possibility of having a defect.

"It's a bit surprising to see this in hair as hair is not a brittle material, but we think it's because of the same reason."