tjära
Tjära, or tar, is a viscous, dark liquid produced by destructive distillation of organic materials, most commonly pine wood (pine tar) or coal (coal tar). The exact composition varies with the source, but both are complex mixtures of hydrocarbons and other organic compounds. Pine tar is obtained by heating pine wood in the absence of air, yielding a resinous product rich in phenolic compounds. Coal tar is produced during the processing of coal, such as in cokemaking, and contains a higher proportion of polycyclic aromatic hydrocarbons (PAHs).
Historically, tar was valued for its ability to waterproof and protect wooden surfaces. It was widely used
Safety and environmental considerations are important. Tar and coal tar contain PAHs, some of which are carcinogenic.