Sep. 12, 2007 — Which type of hair gets the most tangles? Straight or curly? A collaboration between hairdressers and physicists is teasing out the answer.

The roughly 150,000 hairs on our heads are a fascinating but poorly understood phenomenon in the world of physics, says French researcher Jean-Baptiste Masson from the Ecole Polytechnique.

So Masson first conducted a real-life experiment. He asked a few hairdressers to count the tangles in people’s hair late in the afternoon, when tangles have had a chance to develop.

Over the course of three weeks, the hairdressers assessed 123 people with straight hair and 89 with curly hair.

The results were “clear and somewhat surprising,” the physicist said.

Straight hair had almost twice as many tangles, defined as groupings of hair that resist combing, than curly hair.

The average number of tangles was 5.3 for straight hair and 2.9 for curly hair, he reports in the American Journal of Physics.

Masson wanted to understand why this should be, so he developed a mathematical model of how individual hairs interact with each other. The model was inspired by a field of science called polymer dynamics and includes two crucial parameters: the probability of two hairs interacting and the angle at which they meet.

Although curly hairs are more likely to come into contact with other hairs, he says straight hairs tend to have bigger angles between them when they connect. This second factor turns out to be the most important when it comes to tangles, Masson reported. It’s the angle at which hair meets that most determines its likelihood of tangling.

Masson’s work could have implications beyond the end of the hairbrush. One possible application, he says, is in designing Velcro-like products.

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