Another method uses numbers to designate the grade of a pencil. It was originally created by Conté

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Modern pencils do not contain lead as the "lead" of the pencil is actually a mix of finely ground graphite and clay powders. Before the two substances are mixed, they are separately cleaned of foreign matter and dried in a manner that creates large square cakes. Once the cakes have fully dried, the graphite and the clay squares are mixed together using water. The amount of clay content added to the graphite depends on the intended pencil hardness (lower proportions of clay makes the core softer),[29] and the amount of time spent on grinding the mixture determines the quality of the lead. The mixture is then shaped into long spaghetti-like strings, straightened, dried, cut, and then tempered in a kiln. The resulting strings are dipped in oil or molten wax, which seeps into the tiny holes of the material and allows for the smooth writing ability of the pencil. A juniper or incense-cedar plank with several long parallel grooves is cut to fashion a "slat," and the graphite/clay strings are inserted into the grooves. Another grooved plank is glued on top, and the whole assembly is then cut into individual pencils, which are then varnished or painted. Many pencils feature an eraser on the top and so the process is usually still considered incomplete at this point. Each pencil has a shoulder cut on one end of the pencil to allow for a metal ferrule to be secured onto the wood. A rubber plug is then inserted into the ferrule for a functioning eraser on the end of the pencil.[30]
Grading and classification

"Pencil hardness" redirects here.


HB graphite pencils. One is labelled #2 and the other #21/2


A grading chart ranging from 9B to 9H
Many pencils across the world, and almost all in Europe, are graded on the European system using a continuum from "H" (for hardness) to "B" (for blackness), as well as "F", a letter arbitrarily chosen to indicate midway between HB and H. (It is a persistent myth that "F" stands for "Fine"; grade F pencils are no more fine or easily sharpened than any other grade). The standard writing pencil is graded HB.[citation needed] According to Petroski, this system might have been developed 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.[31]
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:
9H    8H    7H    6H    5H    4H    3H    2H    H    F    HB    B    2B    3B    4B    5B    6B    7B    8B    9B
Hardest    ?    Medium    ?    Softest
Koh-i-noor offers twenty grades from 10H to 8B for its 1500 series;[32] Mitsubishi Pencil offers twenty-two grades from 10H to 10B for its Hi-uni range;[33] Derwent produces twenty grades from 9H to 9B for its graphic pencils[34] and Staedtler produces nineteen from 9H to 8B for its Mars Lumograph pencils.[35]
The main market for such wide range of grades are 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. This is reflected in the way pencils are packaged and marketed. For example, for its Graphic pencils Derwent offers three packages of 12 pencils each: Technical (with hard grades from 9H to B), Sketching (with soft grades H to 9B), and Designer (with medium grades 4H to 6B).[citation needed]
Pencils graded using this system are used to measure the hardness and resistance of varnishes and paints. The resistance of a coating (also known as its pencil hardness) is determined as the grade of the hardest pencil that does not mark the coating when pressed firmly against it at a 45 degree angle.[36][37]
Conté/Thoreau[38]
Tone    US    World
#1    B
#2    HB
#21/2 *    F
#3    H
#4    2H
* Also seen as 2-4/8, 2.5, 2-5/10
Another method uses numbers to designate the grade of a pencil. It was originally created by Conté and adopted in the US by John Thoreau, father of Henry Thoreau, in the 19th century.[39]
Although Conté/Thoreau's system is widely accepted, not all manufacturers follow it; for example, Faber-Castell uses a different equivalence table in its Grip 2001 pencils: 1 = 2B, 2 = B, 21/2 = HB, 3 = H, 4 = 2H.
The various graphite pencil grades are achieved by altering the proportion of graphite to clay: the more clay the harder the pencil.[40][41][42] Two pencils of the same grade but different manufacturers will not necessarily make a mark of identical tone nor have the same hardness