Editing Pencil (section)

==Grading and classification==
[[File:TwoHBpencils2 and2 5.jpg|thumb|Two graphite pencils. Both are labelled "HB", but the numeric label differs between "2" and "2{{half}}"]]
[[File:PencilGradingChart.png|thumb|right|A grading chart ranging from 9B to 9H]]

[[#By marking material|Graphite pencils]] are made of a mixture of [[clay]] and [[graphite]] and their darkness varies from light grey to black: the more clay the harder the pencil.<ref>
{{cite web|url=http://www.staedtler.com/upload/graphite_video_eng_16461.mpg |title=Staedtler Pencil, video |accessdate=23 July 2009 |deadurl=yes |archiveurl=https://web.archive.org/web/20130121070208/http://www.staedtler.com/upload/graphite_video_eng_16461.mpg |archivedate=21 January 2013 }} Staedtler.com</ref><ref>[[#Petroski, 1990|Petroski, 1990]]</ref><ref>
{{cite web|url=http://www.pencils.co.uk/heritage.aspx?id=6&sid=1 |title=Derwent Manufacturing Process |publisher=Pencils.co.uk |accessdate=23 July 2009 |deadurl=yes |archiveurl=https://web.archive.org/web/20130517110307/http://www.pencils.co.uk/heritage.aspx?id=6&sid=1 |archivedate=17 May 2013 }}</ref> There is a wide range of grades available, mainly for artists who are interested in creating a full range of tones from light grey to black. Engineers prefer harder pencils which allow for a greater control in the shape of the lead.

Manufacturers distinguish their pencils by grading them, but there is no common standard.<ref>{{cite web |url=https://pencils.com/hb-graphite-grading-scale |title=Archived copy |accessdate=2017-02-05 |deadurl=no |archiveurl=https://web.archive.org/web/20170206105031/https://pencils.com/hb-graphite-grading-scale/ |archivedate=6 February 2017 |df=dmy-all }}</ref> Two pencils of the same grade but different manufacturers will not necessarily make a mark of identical tone nor have the same hardness.<ref>Pencil grades vary "depending upon the manufacturer, when the pencils are made, and the source of graphite and clay. One analyst found that graphitic carbon content, for example, to vary from about 30 to about 65 in a variety of different pencils bearing the same designation." [[#Petroski, 1990|Petroski, 1990]], p. 229</ref>

Most manufacturers, and almost all in Europe, designate their pencils with the letters ''H'' (commonly interpreted as "hardness") to ''B'' (commonly "blackness"), as well as ''F'' (usually taken to mean "fineness", although F pencils are no more fine or more easily sharpened than any other grade. Also known as "firm" in Japan<ref>[http://www.mpuni.co.jp/museum/qa/mistery05.html えんぴつのナゾを解く] {{webarchive|url=https://web.archive.org/web/20151003141714/http://www.mpuni.co.jp/museum/qa/mistery05.html |date=3 October 2015 }}. [[Mitsubishi Pencil Company]](in Japanese)</ref>).  The standard writing pencil is graded ''HB''.<ref>[https://pencils.com/hb-graphite-grading-scale/ "Graphite Grading Scales Explained"] {{webarchive|url=https://web.archive.org/web/20170206105031/https://pencils.com/hb-graphite-grading-scale/ |date=6 February 2017 }}. Pencils.com.</ref> This designation might have been first used in the early 20th century by Brookman, an English pencil maker. It used ''B'' for black and ''H'' for hard; a pencil's grade was described by a sequence or successive Hs or Bs such as ''BB'' and ''BBB'' for successively softer leads, and ''HH'' and ''HHH'' for successively harder ones.<ref>[[#Petroski, 1990|Petroski, 1990]], p.&nbsp;157</ref> The [[Koh-i-Noor Hardtmuth]] pencil manufacturers claim to have first used the HB designations, with ''H'' standing for Hardtmuth, ''B'' for the company's location of [[České Budějovice|Budějovice]], and ''F'' for Franz Hardtmuth, who was responsible for technological improvements in pencil manufacture.<ref>{{cite web | url=http://www.koh-i-noor.cz/en/interesting-information-about-the-company | title=Interesting information about the company | publisher=Koh-I-Noor Hardtmuth | accessdate=12 October 2016 | deadurl=no | archiveurl=https://web.archive.org/web/20161013001501/http://www.koh-i-noor.cz/en/interesting-information-about-the-company | archivedate=13 October 2016 | df=dmy-all }}</ref><ref name="The New Yorker April 28, 2016">{{cite news |last=Norris |first=Mary |authorlink=Mary_Norris_(copy_editor) |url=https://thescene.com/watch/thenewyorker/comma-queen-on-impact |format=Video |title=Comma Queen: On "Impact" |work=The New Yorker |publisher=Condé Nast |date=28 April 2016 |page=2:35 |accessdate=14 May 2016 |deadurl=no |archiveurl=https://web.archive.org/web/20160605053709/https://thescene.com/watch/thenewyorker/comma-queen-on-impact |archivedate=5 June 2016 |df=dmy-all }}</ref>

As of 2009, a set of pencils ranging from a very hard, light-marking pencil to a very soft, black-marking pencil usually ranges from hardest to softest as follows:

{| style="margin:auto; text-align:center;"
|- style="height:10px"
|  style="background:#ddd; width:25px;" | ||  style="background:#ccc; width:25px;" | ||  style="background:#c7c7c7; width:25px;" | ||  style="background:#bbb; width:25px;" | ||  style="background:#b7b7b7; width:25px;" | || style="background:#aaa; width:25px;" | ||  style="background:#999; width:25px;" | ||  style="background:#888888; width:25px;" | || style="background:#777; width:25px;" | ||  style="background:#666; width:25px;" | ||  style="background:#555; width:25px;" | || style="background:#4a4a4a; width:25px;" | ||  style="background:#444; width:25px;" | ||  style="background:#3a3a3a; width:25px;" | || style="background:#333; width:25px;" | ||  style="background:#2a2a2a; width:25px;" | ||  style="background:#222; width:25px;" | || style="background:#1a1a1a; width:25px;" | ||  style="background:#111; width:25px;" | ||  style="background:black; width:25px;"|
|-
| 9H || 8H || 7H || 6H || 5H || 4H || 3H || 2H || H || F || HB || B || 2B || 3B || 4B || 5B || 6B || 7B || 8B || 9B
|-
| style="text-align:left" colspan="3" |Hardest|| colspan=5|→ ||colspan=4|Medium||colspan=5|→||colspan=3 style="text-align:right"|Softest
|}
<!-- Deleted image removed: [[File:pencilGrades.png|left]] -->

[[Koh-i-Noor Hardtmuth|Koh-i-noor]] offers twenty grades from 10H to 8B for its 1500 series;<ref>[https://web.archive.org/web/20071029104124/http://www.koh-i-noor.cz/main/main.php?pageid=3211&lang=4&=&filter=&cat=24&position=30 Koh-i-noor Catalog: Graphite Pencis], koh-i-noor.cz</ref> [[uni-ball|Mitsubishi Pencil]] offers twenty-two grades from 10H to 10B for its Hi-uni range;<ref>[https://web.archive.org/web/20081106131833/http://www.mpuni.co.jp/product/category/pencil/uni/spec.html コード表], mpuni.co.jp (Japanese)</ref> Derwent produces twenty grades from 9H to 9B for its graphic pencils<ref>
{{cite web|url=http://www.pencils.co.uk/products/derwent.aspx?sid=3&p=1 |title=Derwent Graphic |publisher=Pencils.co.uk |accessdate=23 July 2009 |deadurl=yes |archiveurl=https://web.archive.org/web/20090619105057/http://www.pencils.co.uk/products/derwent.aspx?sid=3&p=1 |archivedate=19 June 2009 }}</ref> and [[Staedtler]] produces sixteen from 6H to 8B for its Mars Lumograph pencils.<ref>[http://www.staedtler.com/Mars_Lumograph_gb.Staedtler?ActiveID=2213 Staedtler Mars Lumograph Pencils] {{webarchive|url=https://web.archive.org/web/20070911035033/http://www.staedtler.com/Mars_Lumograph_gb.Staedtler?ActiveID=2213 |date=11 September 2007 }}. Staedtler.com. Retrieved 5 April 2014.</ref>

Numbers as designation were first used by Conté and later by John Thoreau, father of [[Henry David Thoreau]], in the 19th century.<ref>
Conté used integer numbers that started at 1, with higher numbers indicating softer leads, while Thoreau used higher numbers to designate harder leads ([[#Petroski, 1990|Petroski, 1990]], p. 157). It is believed that Thoreau developed independently his method of mixing clay and graphite, and his use of numbers to designate grades is evidence that he was at least aware of Conté methods and tried to reverse engineer them.
Thoreau offered pencils graduated from 1 to 4 in the mid-1800s ([[#Petroski, 1990|Petroski, 1990]], p.&nbsp;119), see also {{cite episode
 | transcripturl=http://www.uh.edu/engines/epi339.htm|transcript=Transcript
 | series=The Engines of Our Ingenuity |serieslink=The Engines of Our Ingenuity
 | number=339
 | title=Thoreau's Pencils
 | airdate=1989
 | credits=John H. Lienhard
 | network=NPR
 | station=KUHF-FM Houston
}} uh.edu</ref>
{| class="wikitable" style="margin:auto; text-align:center;"
|+ Conté/Thoreau<ref>[[#Petroski, 1990|Petroski, 1990]], p.&nbsp;230</ref>
|-
! Tone                        !! US           !! style="text-align:right" | World
|-
|style="background:#444;"|    || #1           || style="text-align:right" | B
|-
|style="background:#555;"|    || #2           || style="text-align:right" | HB
|-
|style="background:#666;"|    || #2½{{sup|*}} || style="text-align:right" | F
|-
|style="background:#777;"|    || #3           || style="text-align:right" | H
|-
|style="background:#888888;"| || #4           || style="text-align:right" | 2H
|-
|colspan=3 | {{sup|*}}Also seen as 2{{sfrac|4|8}}, 2.5, 2{{sfrac|5|10}}
|}

Although Conté/Thoreau's equivalence table is widely accepted{{cn|date=October 2017}}, not all manufacturers follow it; for example, Faber-Castell uses a different equivalence table in its ''Grip 2001'' pencils: 1 = 2B, 2 = B, 2½ = HB, 3 = H, 4 = 2H.

=== Pencil hardness test ===
Graded pencils can be used for a rapid test that provides relative ratings for a series of coated panels but can't be used to compare the pencil hardness of different coatings. This test defines a "pencil hardness" of a coating as the grade of the hardest pencil that does not permanently mark the coating when pressed firmly against it at a 45 degree angle.<ref>This testing method is approved by the [[International Organization for Standardization|ISO]] as standard ISO 15184:1998 Paints and varnishes – Determination of film hardness by pencil test [https://www.iso.org/standard/55329.html?browse=tc ISO.org] {{webarchive|url=https://web.archive.org/web/20171026111219/https://www.iso.org/standard/55329.html?browse=tc |date=26 October 2017 }}. See [http://www.pra-world.com/technical/testingphysicalhardness.htm pra-world.com]  {{webarchive|url=https://web.archive.org/web/20070929224302/http://www.pra-world.com/technical/testingphysicalhardness.htm |date=29 September 2007 }} for a description of the test. Unfortunately the hardness of pencils is not standardised. For this reason the standard specifies various brands of pencils that are to be used in this test.</ref><ref>
{{Cite journal
 |author      = Mac Simmons
 |title       = The Pencil Hardness Test
 |journal     = Woodwork
 |date        = April 2000
 |page        = 76
 |url         = http://www.pencilpages.com/articles/simmons.htm
 |accessdate  = 13 September 2007
 |deadurl     = no
 |archiveurl  = https://web.archive.org/web/20070928042339/http://www.pencilpages.com/articles/simmons.htm
 |archivedate = 28 September 2007
 |df          = dmy-all
}}</ref> For standardized measurements, there are [[Mohs hardness]] testing pencils on the market. <!-- Sorry, no ref. A Google search shows many brands, such as http://mahavirgems.in/Gem-Hardness-Pencils-1-to-10-on-Moh's-Scale, but I couldn't find an overarching discussion. -->

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