The bow hair corresponds not only to the hairs on the artist’s paintbrush but also is the “right-hand equivalent” to the fingertips for the left hand: it is that part of our “body” that actually touches the string. We will continue to use these analogies to discuss the significance of the different bowhair variables: tension, angle, volume, width and “string-gripping characteristics”.
Imagine if our finger tips were very hard and insensitive: this would be like having the bowhair excessively tight. If the bow hair is too tight, we lose flexibility, cushioning, suppleness. An overtight bow becomes hypersensitive and hyper-reactive to even small changes of pressure. Like a tight trampoline or a stiff diving board, its natural reaction to pressure is to bounce back violently into the air. A tight bow is hard to keep smoothly and steadily “into” the string, especially in soft playing.
The hair angle (the amount of bow-hair in contact with the string) corresponds to the width of the artists paint-brush. This is not only significant for the density of the sound but is also important in determining the bouncing characteristics of the bow. Turning the bowstick so that less hairs are touching the string, has the effect of reducing the bow’s tendency to bounce. For gentle, careful bow placements and note starts, we can use this characteristic to good advantage: the less hair we place on the string, the easier it becomes to make gentle, cushioned bow placements and note starts.
The amount of hair in contact with the string is determined by two factors: the hair width and the angle at which we place the bow on the string.