False! It’s actually more complex and interesting than that. If you look at a piece of horsehair through a microscope, on its surface you see more what looks like tree bark and nothing that looks like barbs or hooks.

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As you can see in the micrographs by acoustical engineer Françoise Rocaboy, horsehair is actually covered with flat scales which are extremely tiny. These flat scales are only about 5 micrometers high, which to put into perspective, is about 1/400 the width of a typical violin E string. What this means is that in comparison with the size of an instrument’s strings, horsehair has an essentially flat scale structure, and therefore can’t latch onto strings.

 

The scales are, however, large enough to hold tiny rosin particles in place. During bowing, the particles of rosin get trapped between the string and the bow hair, and due to the heat produced, the rosin becomes very sticky and momentarily glues the hair to the string. This moves the string to the side, then eventually the bond breaks and this starts the oscillation of the string.

 

So there you are—instead of barbs, there are hair scales and hot glue!