- Pitch (resin)
Pitch is the name for any of a number of highly viscous
liquids which appear solid. Pitch can be made from petroleumproducts or plants. Petroleum-derived pitch is also called bitumen. Pitch produced from plants is also known as resin. Products made from plant resin are also known as rosin.
Tar pitch appears solid, and can be shattered with a hard impact, but it is actually fluid. Pitch flows at room temperature, but extremely slowly. The
pitch drop experimenttaking place at University of Queenslandis a long-term experiment which measures the flow of a piece of pitch over many years. For the experiment, pitch was put in a glass container with a hole in the bottom, and allowed to slowly drip out. Since the pitch was allowed to start dripping in 1930, only eight drops have fallen. It was calculated in the 1980s that the pitch in the experiment has a viscosity approximately 100 billion (1011) times that of water. [ [http://www.physics.uq.edu.au/physics_museum/pitchdrop.shtml The Pitch Drop Experiment ] ]
Pitch was traditionally used to help
caulkthe seams of wooden sailing vessels (see shipbuilding). It was heated, then put into a container with a very long spout. The word "pitcher" is said to derive from this long spouted container used to pour hot pitch. [ [http://www.maritime.org/conf/conf-kaye-tar.htm Pine Tar; History And Uses ] ] Pitch was also used to waterproofwooden containers, and is sometimes still used in the making of torches.
It is jet-black in color, and may be the origin of the term "pitch-black."
The heating (dry distilling) of wood causes
tarand pitch to drip away from the wood and leave behind charcoal. Birchbark is used to make particularly fine tar. Tarand pitch are often used interchangeably. However, pitch is considered more solid while tar is more liquid. Traditionally, pitch for waterproofing buckets, barrels and small boats was drawn from pine.
* [http://www.physics.uq.edu.au/pitchdrop/pitchdrop.shtml The Pitch Drop Experiment]
* [http://www.maritime.org/conf/conf-kaye-tar.htm Pine Tar Production]
* [http://www.hunter-gatherer.org/psg/crafts.html#13.6 Primitive tar and charcoal production]
* [http://www.deliberatelife.com/index.php?option=com_content&task=view&id=147&Itemid=70 Simple pine pitch making]
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