|
For other uses of this word, see tar (disambiguation). Tar is a viscous black liquid derived from the destructive distillation of organic matter. Most tar is produced from coal as a byproduct of coke production, but it can also be produced from petroleum, peat or wood. The use of the word "tar" is frequently a misnomer. Naturally occurring "tar pits" (e.g. the La Brea Tar Pits in Los Angeles) actually contain asphalt, not tar, and are more accurately known as asphalt pits. Tar sand deposits contain bitumen rather than tar, as does the Tar Tunnel in Shropshire. "Rangoon tar", also known as "Burmese Oil" or "Burmese Naphtha", is actually petroleum. In English and French, "tar" means primarily the coal derivative, but in northern Europe, it refers primarily to the wood distillate, which is used in the flavoring of candy (among other things). Tar, of which petroleum tar is the most effective, is used in treatment of psoriasis. Tar is a disinfectant substance, and used as such. Petroleum tar was also used in ancient Egyptian mummification circa 1000 BC. In archaic Finland tar was considered a panacea reputed to heal "even those cut in twain through their midriff". Tar was a vital component of the first sealed, or "tarmac", roads. It was also used as seal for roofing shingles and to seal the hulls of ships and boats. For millenia wood tar was used to waterproof sails and boats, but today sails made from inherently waterproof synthetic substances have negated the need for sail sealing. Wood tar is still used to seal traditional wooden boats and the roofs of historical shingle-roofed churches, as well painting exterior walls of log buildings. Wood tar is also available diluted as tar water, which has numerous uses:
Production The heating (dry distilling) of pine wood causes tar and pitch to drip away from the wood and leave behind charcoal. Birchbark is used to make particularly fine tar (tökötti). Tar and pitch are often used interchangeably. However, pitch is considered more solid while tar is more liquid. The by-products of tar are turpentine and charcoal. While deciduous tree woods are subjected the destructive distillation, the by-products are methanol (wood alcohol) and charcoal. See also Sources .... | ||||||||
|
| |||||||||
 |
|
| |