How To Choose Rosin Series - Part 1 - How Rosin Works

Diagram of "The Hemholtz Motion"

How Rosin Works

A lot of people have misconceptions when it comes to how the bow creates sound on a stringed instrument. Many people have the impression that the bow hair has scales on it that grab the string to make it vibrate, which is close, but not quite correct. A bow can’t make noise on a string by itself with only the horsehair. The way to get sound out of the instrument is the addition of rosin to the bow hair, which acts as an adhesion.

When applied, this sticky rosin grabs the string. So how does that make sound? When you move a bow across a string, the string sticks to the rough surface of the bow where the rosin has been applied and gets dragged according to the direction of the bow’s movement. This dragging motion creates a tiny kink which travels the length of the string towards the bow.

When the kink reaches the bow, the string is released and rebounds in the opposite direction, only for the whole process to start all over again. When the process is repeated in quick succession, the string vibrates at whatever frequency it is tuned to. This motion is called “The Hemholtz Motion”, and here is a little diagram that displays how it works.

For more information on rosin, such as "Why color makes a difference and good considerations for choosing it", stay “tuned” for parts 2 and 3 of our series!