View source for Chemistry:Pitch (resin)

{{Short description|Resin}}
[[File:McKittrick Tar Seep North of Highway 58.jpg|thumb|Natural bitumen pitch, from the tar pit above the McKittrick Oil Field, Kern County, California]]

'''Pitch''' is a viscoelastic [[Chemistry:Polymer|polymer]] which can be natural or manufactured, derived from [[Chemistry:Petroleum|petroleum]], [[Chemistry:Coal tar|coal tar]],<ref>{{Cite web |url=http://echa.europa.eu/documents/10162/13630/trd_rar_env_netherlands_pitch_en.pdf |title=Coal-Tar Pitch, High Temperature |access-date=2014-06-09 |archive-date=2021-05-05 |archive-url=https://web.archive.org/web/20210505095450/https://echa.europa.eu/documents/10162/13630/trd_rar_env_netherlands_pitch_en.pdf |url-status=dead}}</ref> or plants. Pitch produced from petroleum may be called [[Chemistry:Bitumen|bitumen]] or [[Chemistry:Bitumen|asphalt]], while plant-derived pitch, a resin, is known as rosin in its solid form. [[Chemistry:Tar|Tar]] is sometimes used interchangeably with pitch, but generally refers to a more liquid substance derived from coal production, including [[Chemistry:Coal tar|coal tar]], or from plants, as in [[Chemistry:Pine tar|pine tar]].<ref>{{Cite web |title=CPC Definition - C10C Working-up Pitch, Asphalt, Bitumen, Tar; Pyroligneous Acid |url=https://www.uspto.gov/web/patents/classification/cpc/html/defC10C.html |access-date=12 August 2023 |website=Classification Resources |publisher=United States Patent and Trademark Office |date=November 2016}}</ref>

== Uses ==
[[File:Beckholmen Bucket of pitch.JPG|thumb|upright|Bucket of pitch for use on ships]]

Pitch, a traditional naval store, was traditionally used to help caulk the seams of wooden sailing vessels (see [[Engineering:Shipbuilding|shipbuilding]]).  Other important historic uses included coating earthenware vessels for the preservation of wine, waterproofing wooden containers, and making [[Earth:Torch|torch]]es. Petroleum-derived pitch is black in colour, hence the adjectival phrase, "pitch-black".<ref>''Oxford English Dictionary'' "pitch, n.1", phrases P1</ref>

The viscoelastic properties of pitch make it well suited for the polishing of high-quality optical lenses and mirrors. In use, the pitch is formed into a lap or polishing surface, which is charged with iron oxide (Jewelers' rouge) or cerium oxide. The surface to be polished is pressed into the pitch, then rubbed against the surface so formed. The ability of pitch to flow, albeit slowly, keeps it in constant uniform contact with the optical surface.

[[Engineering:Chasers pitch|Chasers pitch]] is a combination of pitch and other substances, used in jewelry making.

== Viscoelastic properties ==
[[Image:University of Queensland Pitch drop experiment-white bg.jpg|thumb|left|upright|The pitch shown in this University of Queensland pitch drop experiment has a viscosity approximately 230 billion times that of water.]]

Naturally occurring [[Chemistry:Bitumen|asphalt]]/bitumen, a type of pitch, is a viscoelastic [[Chemistry:Polymer|polymer]]. 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 [[Physics:Pitch drop experiment|pitch drop experiment]] taking place at University of Queensland is a long-term experiment which demonstrates 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 nine drops have fallen. It was calculated in the 1980s that the pitch in the experiment has a [[Physics:Viscosity|viscosity]] approximately 230 billion (2.3×10<sup>11</sup>) times that of water.<ref>{{cite web |url=http://smp.uq.edu.au/content/pitch-drop-experiment |title=The Pitch Drop Experiment |website=University of Queensland}}</ref> The eighth drop fell on 28 November 2000, and the ninth drop fell on 17 April 2014.<ref name="UniQueensland">{{cite journal |last1=Biever |first1=Celeste |first2=Lisa |last2=Grossman |date=17 April 2014 |title=Longest experiment sees pitch drop after 84-year wait |journal=New Scientist |url=https://www.newscientist.com/article/dn25441-longest-experiment-sees-pitch-drop-after-84year-wait.html |access-date=23 June 2014}}</ref> Another experiment was started by a colleague of Nobel Prize winner [[Biography:Ernest Walton|Ernest Walton]] in the physics department of Trinity College in Ireland in 1944. Over the years, the pitch had produced several drops, but none had been recorded. On July 11, 2013, scientists at Trinity College caught pitch dripping from a funnel on camera for the first time.<ref>{{cite web |url=http://www.rte.ie/news/2013/0717/463097-trinity-college-dublin-pitch-experiment/ |title=Trinity College experiment succeeds after 69 years |publisher=RTÉ News |date=24 July 2013 |access-date=23 June 2014}}</ref>

[[Organization:Winchester College|Winchester College]] has a 'pitch glacier' demonstration which has been running since 21 July 1906, but does not have records of regular measurements.<ref>{{cite book |last1=Gregory |first1=Martin |editor1-last=Foster |editor1-first=Richard |title=50 Treasures from Winchester College. |publisher=SCALA |isbn=9781785512209 |page=123 |chapter=Pitch Flow Demonstrations, 1906 |year=2019 }}</ref>

== Production ==
The heating ([[Chemistry:Dry distillation|dry distilling]]) of wood causes [[Chemistry:Tar|tar]] and pitch to drip away from the wood and leave behind [[Chemistry:Charcoal|charcoal]]. Birchbark is used to make birch-tar, a particularly fine tar. The terms tar and pitch are often used interchangeably. However, pitch is considered more solid, while tar is more liquid. Traditionally, pitch that was used for waterproofing buckets, barrels and ships was drawn from [[Biology:Pine|pine]]. It is used to make [[Chemistry:Cutler's resin|Cutler's resin]].

A 10th-century redaction of an earlier Greek Byzantine agricultural work brings down the ancient method of applying pitch to ceramic wine casks:
<blockquote>[A wood-based pitch]<ref group=note>The more commonly used wood resin used for making pitch was extracted from the lentisk and from [[Biology:Pine|pine]], and was first washed in a lixivium of ashes. (''Geoponika'', vol. 1, p. [https://archive.org/details/Geoponica01/page/n238/mode/1up 202]. For an extraction method, see [[Chemistry:Dry distillation#Wood|Dry distillation]].</ref> is put into an earthen vessel, and it is put over a small fire in the sun, then some hot water percolated through wood-ashes is poured on it, and the pitch is stirred; when it has afterward stood, it is poured out after two hours, then there is as much water again poured in. Having therefore done this thrice every day for three days and having taken up the moisture on the surface, they make the pitch that is left exceedingly good. Dry pitch is also bitter, but being boiled with wine it becomes more useful; [...] and having boiled the mixture to a third part, they use it as properly qualified: but some throw wood-ashes into it and boil it down.<br> In Italy they use pitch of this kind: forty [[Physics:Mina (unit)#The Greek mina|minæ]]<ref group=note>The Attic mina weighed 436.6 grams (15.4 ounces). Forty minæ was equivalent in weight to {{convert|17.4|kg|lb}}. See: {{cite book |last1=Sherwood |first1=Andrew |last2=Nikolic |first2=Milorad |last3=Humphrey |first3=John |last4=Oleson |first4=John |author4-link=John Peter Oleson |title=Greek and Roman Technology A Sourcebook of Translated Greek and Roman Texts |date=1997 |edition=1 |publisher=[[Company:Routledge|Routledge]] |page=764 |language=en |isbn=0-415-06136-9}}</ref> of pitch, one of [[Chemistry:Beeswax|wax]], eight [[Dram (unit)#Ancient unit of mass|drams]]<ref group=note>One Attic [[Ancient Greek units of measurement#Weight|Greek drachma]] was a weight of about 4.37&nbsp;[[Gram|gram]]s; eight drams therefore being the equivalent of 35 g. (1.2 ounces).</ref> of sal ammoniac, six drams of manna.<ref group=note>The sense here is to the crystallized products of plant sap.</ref> Thus, having pounded them and boiled them together, they sprinkle eight ounces (''uncia'')<ref group=note>The Attic ''uncia'' was equivalent in weight to about 27.4 grams. Eight ounces would therefore be the equivalent of 219 grams (7.7 UK ounces).</ref> of well-ground [[Biology:Fenugreek|fenugreek]] over them and they pitch the cask with them when they are well mixed.<ref>{{cite book |translator-last=Owen |translator-first=T. |translator-link=Thomas Owen (priest) |title=Geoponika - Agricultural Pursuits |volume=1 |date=1805 |publisher=[[Organization:University of Oxford|University of Oxford]] |location=London |language=en |url=https://archive.org/details/Geoponica01/page/n13/mode/1up |pages=[https://archive.org/details/Geoponica01/page/n235/mode/1up 200–201]}}</ref></blockquote>

The ceramic ware was pitched, both inside and out, immediately while they were removed from the kiln and still hot.<ref>{{cite book |translator-last=Owen |translator-first=T. |translator-link=Thomas Owen (priest) |title=Geoponika - Agricultural Pursuits |volume=1 |date=1805 |publisher=[[Organization:University of Oxford|University of Oxford]] |location=London |language=en |url=https://archive.org/details/Geoponica01/page/n13/mode/1up |pages=[https://archive.org/details/Geoponica01/page/n234/mode/1up 198]}}</ref>

==Literary references==
The ability of pitch to contaminate those in contact with it is mentioned by Dogberry, a character in Shakespeare's ''Much Ado About Nothing'',<ref>Shakespeare, W., ''Much Ado About Nothing'', Act III, Scene III, line 61</ref> and the same point is made in a speech by Falstaff in Henry IV, Part 1,<ref>Shakespeare, W., ''Henry IV, Part 1'', Act II, Scene IV, line 460</ref> who refers to "ancient writers" who have made this observation. The [[Religion:Jews|Jewish]] [[Religion:Deuterocanonical books|deuterocanonical]] Book of Sirach states that "whoever touches pitch gets dirty, and whoever associates with a proud person becomes like him".<ref>{{bibleverse||Sirach|13:1|NRSV}}</ref><ref>{{cite book | last = Collins | first =  J. J. | title = 44. Ecclesiasticus, or The Wisdom of Jesus Son of Sirach | editor1= Barton, J. | editor2= Muddiman, J. | year= 2001  | url = https://b-ok.org/dl/946961/8f5f43 | work = The Oxford Bible Commentary| page =  677}}</ref>

== See also ==
* Asphaltene
* [[Chemistry:Creosote|Creosote]]
* [[Chemistry:Pine tar|Pine tar]]
* [[Chemistry:Tar|Tar]]

==Notes==
{{reflist|group=note}}
== References ==
{{Reflist}}

== External links ==
{{wikt|pitch}}
* [http://smp.uq.edu.au/content/pitch-drop-experiment 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]

{{Non-timber forest products}}
{{Wood products}}

[[Category:Materials]]
[[Category:Chemical mixtures]]
[[Category:Amorphous solids]]

{{Sourceattribution|Pitch (resin)}}