Rosin: It is the oil flowing from the inside of pine tree trunk, which melts into water at high temperature, and becomes a massive solid (with no fixed melting point) after drying, and its color is brown and crimson.

It is an important chemical raw material.

In daily life, it is mainly used as flux for soldering circuit boards.

In terms of musical instruments, rosin is applied to the bow hair of the erhu, violin, Ma Touqin and other bowstring instruments to increase the friction between the bow hair and the strings.