Pitch (resin)
Pitch is the name for any of a number of viscoelastic, solid
Solid is one of the three classical states of matter . It is characterized by structural rigidity and resistance to changes of shape or volume. Unlike a liquid, a solid object does not flow to take on the shape of its container, nor does it expand to fill the entire volume available to it like a...

A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...

s. Pitch can be made from petroleum
Petroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...

 products or plants. Petroleum-derived pitch is also called bitumen. Pitch produced from plants is also known as resin
Resin in the most specific use of the term is a hydrocarbon secretion of many plants, particularly coniferous trees. Resins are valued for their chemical properties and associated uses, such as the production of varnishes, adhesives, and food glazing agents; as an important source of raw materials...

. Products made from plant resin are also known as rosin
.Rosin, also called colophony or Greek pitch , is a solid form of resin obtained from pines and some other plants, mostly conifers, produced by heating fresh liquid resin to vaporize the volatile liquid terpene components. It is semi-transparent and varies in color from yellow to black...


Pitch was traditionally used to help caulk the seams of wooden sailing vessels (see shipbuilding
Shipbuilding is the construction of ships and floating vessels. It normally takes place in a specialized facility known as a shipyard. Shipbuilders, also called shipwrights, follow a specialized occupation that traces its roots to before recorded history.Shipbuilding and ship repairs, both...

). Pitch was also used to waterproof wooden containers, and is sometimes still used in the making of torch
A torch is a fire source, usually a rod-shaped piece of wood with a rag soaked in pitch and/or some other flammable material wrapped around one end. Torches were often supported in sconces by brackets high up on walls, to throw light over corridors in stone structures such as castles or crypts...


Petroleum-derived pitch is black in color, hence the adjectival phrase, "pitch-black".

Viscoelastic properties

Tar pitch is a viscoelastic polymer
A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...

. This means that even though it seems to be solid at room temperature and can be shattered with a hard impact, it is actually fluid and will flow over time, but extremely slowly. The pitch drop experiment
Pitch drop experiment
The pitch drop experiment is a long-term experiment which measures the flow of a piece of pitch over many years. Pitch is the name for any of a number of highly viscous liquids which appear solid, most commonly bitumen...

 taking place at University of Queensland
University of Queensland
The University of Queensland, also known as UQ, is a public university located in state of Queensland, Australia. Founded in 1909, it is the oldest and largest university in Queensland and the fifth oldest in the nation...

 is a long-term experiment
Long-term experiment
A long-term experiment is an experimental procedure that runs through a long period of time, in order to test a hypothesis or observe a phenomenon that takes place at an extremely slow rate....

 which measures the flow of a piece of pitch over many years. For the experiment, pitch was put in a glass funnel 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 230 billion
1000000000 (number)
1,000,000,000 is the natural number following 999,999,999 and preceding 1,000,000,001.In scientific notation, it is written as 109....

 (2.3x1011) times that of water.


The heating (dry distilling
Dry distillation
Dry distillation is the heating of solid materials to produce gaseous products . The method may or may not involve pyrolysis/thermolysis. The products are condensed and collected. This method usually requires higher temperatures than classical distillation. The method has been used to obtain...

) of wood causes tar
Tar is modified pitch produced primarily from the wood and roots of pine by destructive distillation under pyrolysis. Production and trade in tar was a major contributor in the economies of Northern Europe and Colonial America. Its main use was in preserving wooden vessels against rot. The largest...

 and pitch to drip away from the wood and leave behind charcoal
Charcoal is the dark grey residue consisting of carbon, and any remaining ash, obtained by removing water and other volatile constituents from animal and vegetation substances. Charcoal is usually produced by slow pyrolysis, the heating of wood or other substances in the absence of oxygen...

. Birchbark is used to make a particularly fine tar. Tar and pitch are often used interchangeably. However, pitch is considered more solid while tar is more liquid. Traditionally, pitch used for waterproofing buckets, barrels and small boats was drawn from pine. It is used to make Cutler's resin
Cutler's resin
Cutler's resin is a synthetic resin made of pine pitch, beeswax, and sawdust or carnauba wax used for centuries to attach knife handles. It is used as both an adhesive and for waterproofing. The word cutler means "one who makes knives"....


External links

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