Tar

Tar is a dark brown or black liquid that is thick and flows slowly. It is made from many different organic materials through a process called destructive distillation. This means heating the materials so strongly that they break down into tar and other products.

We can get tar from many carbon-rich materials such as coal, wood, petroleum, and peat. One important kind of tar comes from coal and is called coal tar. This is made when coal is turned into coke, another product used in industry.

Tar is also related to mineral products that come from fossil hydrocarbons like petroleum. These materials have been buried deep in the Earth for millions of years and can be processed to make similar substances.

Terminology

"Tar" and pitch can be used to mean the same thing. Asphalt, which happens naturally, may be called either "mineral tar" or "mineral pitch". We often use "tar" for liquids and "pitch" for solids. Both words describe thick forms of asphalt, like the kind found in natural tar pits, such as the La Brea Tar Pits in Los Angeles. "Rangoon tar", also called "Burmese oil" or "Burmese naphtha", is a type of petroleum. Oil sands in Alberta, Canada, made of asphalt, are often called "tar sands".

Wood tar

Further information: Pine tar and Birch tar

Wood tar has been used since ancient times to keep water out of boats, ships, sails, and roofs. It was especially important in places like Scandinavia, where people made tar from wood as a valuable product. Even today, wood tar is used in foods like candy and alcohol, and it can help stop tiny harmful things from growing.

People have known how to make tar from wood since ancient Greece and likely much earlier. Making tar from pine wood leaves behind useful by-products like turpentine and charcoal. Special ovens called tar kilns were used in Scandinavia to produce tar from wood by heating it without letting it catch fire.

Tar is still used today to protect wooden roofs, boats, and buildings. It can also be found in some medicines and soaps. In Finland, wood tar was once thought to help with many health problems. Tar mixed with other substances can also be used to protect and color wood.

Coal tar

Main article: Coal tar

Coal tar used to be made at places called gasworks. Tar made from coal or oil can be harmful because it contains a chemical called benzene. Even so, very small amounts of coal tar are sometimes used to help treat skin problems like psoriasis. This kind of tar has a strong smell.

Coal tar is listed as a dangerous material by the United Nations.