Everything about Tar totally explained
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.
Types of tar
General
The word "tar" is used to describe several distinct substances. Naturally occurring "
tar pits" (for example 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 various mixtures of sand (or rock) with
bitumen or
heavy crude oil rather than tar, as does the
Tar Tunnel in
Shropshire. "Rangoon tar", also known as "Burmese Oil" or "Burmese Naphtha", is actually
petroleum. "Tar" and "
pitch (resin)" are sometimes used interchangeably; however, pitch is considered more solid while tar is more liquid.
Coal
In English and French, "tar" is a substance primarily derived from coal. It was formerly one of the products of a
gasworks. Tar made from coal or petroleum is considered
toxic and
carcinogenic because of its high
benzene content, however,
coal tar in low concentrations is used as a
topical medicine. Coal and petroleum tar has a pungent odor.
Coal tar is listed at
number 1999 in the
United Nations list of
dangerous goods.
Wood
In
Northern Europe, the word "tar" refers primarily to a substance
derived from wood, which is used even as an additive in the flavoring of candy and other foods. Wood tar is
microbicidial and has a pleasant odor.
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). The by-products of wood tar are
turpentine and
charcoal. When deciduous tree woods are subjected to destructive distillation the products are
methanol (wood alcohol) and
charcoal.
Uses
Tar is used in treatment of the skin disease
psoriasis, where coal tar is the most effective. Tar is also a general disinfectant. Petroleum tar was also used in
ancient Egyptian
mummification circa
1000 BC.
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 millennia wood tar was used to waterproof
sails and boats, but today sails made from inherently waterproof synthetic substances have negated the need for tar. 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.
In
Finland wood tar was once considered a
panacea reputed to heal "even those cut in twain through their midriff". A Finnish proverb states that
if sauna, vodka and tar won't help, the disease is fatal. Wood tar is used in traditional Finnish medicine because of its microbicidial properties.
Wood tar is also available diluted as
tar water, which has numerous uses:
- As a flavoring for candies (for example Terva Leijona) and alcohol (Terva Viina)
- As a spice for food, like meat
- As a scent for saunas. Tar water is mixed into water that's turned to steam to the air
- As an anti-dandruff agent in shampoo
- As a component of cosmetics
Mixing tar with linseed oil
varnish produces tar paint. Tar paint has a translucent brownish hue, and can be used to saturate and tone wood and protect it from weather. Tar paint can also be toned with various pigments, producing translucent colours and preserving the wood texture. Because of its paint-like properties, wet tar shouldn't be touched with bare skin, as it can dry to produce a permanent stain. However, in some cases, paint thinner has been known to remove it.
Further Information
Get more info on 'Tar'.
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