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 on ships, fences, roofs and other timber structures, and was also applied to rope and leather. Coal tar products, including the related creosote, were extensively used as wood preservatives and in road and railway infrastructure. Over time, concerns about health and environmental risks have reduced reliance on raw tar in many countries, with modern practices favoring regulated preservatives and alternative treatments.

Safety and environmental considerations are important. Tar and coal tar contain PAHs, some of which are carcinogenic. Long-term skin contact, inhalation of fumes, or improper disposal pose health and environmental risks. Handling typically requires protective equipment, good ventilation, and adherence to waste disposal regulations. In contemporary use, tar is often avoided for new installations in favor of safer preservatives, though it remains of historical and artisanal interest.

See also: Pine tar, Coal tar, Creosote, Wood preservation.