What is the stick-slip effect?
A typical bow is strung using horse hair, although synthetic hairs are increasingly used nowadays. When playing, these bow hairs slide over the string and produce heat. This heat melts the rosin. As soon as it cools down, the bow hairs stick to the string. The bow hair then moves with the string until the force equilibrium is exceeded. When this happens, the bonded area of “hair-rosin-string” breaks open and the string vibrates back in the other direction. This action produces more heat, the rosin melts and the process starts again. It is known as the “stick & slip effect”.