Gum rosin is an organic compound of monoterpene, turpentine and resin acid. Also known as colophony or rosin, it is a solid form of pine oleoresin from pine trees (mostly conifers). It is produced by heating fresh liquid resin in order to vaporize the volatile liquid terpene components. It is semi-transparent and varies in color from pale yellow to amber. Rosin is brittle at room temperature, but melts at higher temperatures. It is insoluble in water and soluble in organic solvents. Gum Rosin also has a faint piny odour. It consists mostly of different resin acids, especially abietic acid.