The natural resin is collected from pine trees. Pieces of natural resin are put into a heated pot and, through a special process, rosin is produced.
The violin bow hair is generally white horsetail, with some rosin evenly rubbed on the bow hair. With this, you can draw beautiful sounds from the violin.
When the bow is not in use, unscrew the bow until the hairs are without tension; this condition is called the rest condition. Before playing, just tighten the screw a few times so the bow hairs are about medium tight, although each player may have their own preferences. See Fig. 8: