Microscopic Hooks on Bow Hair?

For me, weekends equal teaching. This means that weekends often involve me telling other people something they have not heard before. Sometimes, I hear something I have not heard before.

A student came in today and told me about the microscopic hooks on her bow hair which pluck at the strings. These apparently become worn down over time, which is why bow rehairs are necessary even if the bow still has hair on it.

I opened my mouth to object and then could only stare incredulously for a few moments, my eyes narrowed at the bizarrely entertaining and horrifying thought, as I imagined that. I wrapped up my imagination and finally said, “What a curious idea. Bow hair is regular hair from a horse’s tail. I’d think that the hair would get caught on all sorts of things all the time, and the horse probably would not enjoy that.”

The student, who had been giggling at my expression, agreed and felt glad that horses did not have to suffer from their tails being caught at random and inopportune moments. Then, we began the lesson properly.

Although I have not studied this topic or thought about this idea at all, I feel certain that it is not true that the hair on my bow has tiny microscopic hooks which work to “grip” at my strings and thereby produce sound. During my quick browsing on the topic, just to make sure that my thoughts are not wrong, I came across an Analysis of Bow-Hair Fibres.

Before I talk about the article, it is necessary to explain a bit about hair. A strand of hair is made up of three parts: the medulla, the cortex, and the cuticle. The medulla is the center area, the cortex is the middle later, and the cuticle is the outer layer. The hair cuticle, which is what interests us here, is made up keratin plates.

Now to the research!

The 8-page study is a quick read and quite interesting— to me, at least— but I shall skip to the part which interests us. In the section titled “The Structure of Hair”, the researchers point out that the stickiness and slipperiness of the bow is caused by rosin and that how well the rosin bonds to the hair depends on the chemical properties of the cuticle rather than the shape of the keratin plates… which is essentially what I think my student called the “microscopic hooks”.

In the researchers’ bowing test, they found data which indicated that rosin had a large effect on sound. On the other hand, as the study remarks in its summary, “the influence of the scalation and the size of the keratin plates had a rather marginal effect on the produced sound.”

(For those who do not feel like reading research but have wondered about your bow hair, I encourage you to visit the study and scroll to the pictures. There are some close-up pictures of various types of bow hair in the section titled “Structure and Surface Analysis”. You can see that the size and shape of the keratin plates on the hairs differ. While that may not greatly impact sound, it is interesting to see.)

At any rate, I still believe there are no “microscopic hooks” on bow hair which grip the string for me— at least, not effectively enough for me to think much of it or about it. First, my intuition tells me it is unlikely. Second, there is a research article which explicitly makes reference to this belief and refutes it through data. Third, if better microscopic hooks worked better at gripping a bow, I am sure I would have heard a lot more about the quality of bow hair the same way I heard about buying good strings. A few beginner students who have more money than inclination or time to practice would be asking what sort of bow hair is best in the same way they sometimes obsess over better string combinations.