... of natural resin, its general formula is C20H30O2Gum rosin is made of natural resin, its general ... formula is C20H30O2. Gum rosin also called colophony, is a solid form of ... color from yellow to black. At room temperature rosin is brittle, but it melts at stove-top ... different resin acids, especially abietic acid. Gum rosin is an important raw material for the manufacture ...