Resin.
To set the strings in vibration, the hair of the bow must be rubbed with resin. Its German name “Kolophonium” is derived from the Grecian town Kolophon, from whence it was first procured. The unprepared hair of a new bow requires a small quantity of powdered resin rubbed into it. Before the bow is used, the hair should be tried upon some instrument not in use, or upon a stretched string. During the ordinary rubbing upon the hair, care must be taken that the resin is not rubbed hard, but allowed to glide lightly over the hair.
It is very usual to hold the resin with the left and the bow with the right hand. In this way the fingers of the left hand become sticky with resin dust, which is detrimental to the stopping, and also soils the strings and fingerboard. It is better, therefore, to reverse this procedure. Good resin is supplied by Gand and Bernadel in Paris, Hammig in Leipsic, Pfab and Diel in Hamburg, and others. The most suitable holders are those which open on two sides, and are also provided with a cover.[9]