Eraser attached
Drawing of pencil with an attached eraser from its patent application.
On March 30, 1858, Hymen Lipman received the first patent for attaching an eraser to the end of a pencil.In 1862 Lipman sold his patent to Joseph Reckendorfer for $100,000, who went to sue the pencil manufacturer Faber for infringement. In 1875 the Supreme Court of the United States ruled against Reckendorfer declaring the patent invalid.
The metal band used to mate the eraser with pencil is called a ferrule.
Manufacture
Modern pencils are made industrially by mixing finely ground graphite and clay powders, adding water, forming long spaghetti-like strings, and firing them in a kiln (thermally insulated chambers). The resulting strings are dipped in oil or molten wax, which seeps into the tiny holes of the material, resulting in smoother writing. 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.
Grading and classification
Two HB pencils. One is labelled #2 and the other #2 1/2.
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" (for fine point). The standard writing pencil is graded HB. According to Petroski this system might have been developed in the early 1900s 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.
Today 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; Derwent produces twenty grades from 9H to 9B for its Graphic pencils and Staedtler produces nineteen from 9H to 8B for its Mars Lumograph pencils. 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).
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.
Another common method uses numbers to designated the grade of a pencil. It was originally created by Conté and adopted in the United States by Thoreau in the 19th century.The following table shows approximate equivalences between the different systems:
Drawing of pencil with an attached eraser from its patent application.
On March 30, 1858, Hymen Lipman received the first patent for attaching an eraser to the end of a pencil.In 1862 Lipman sold his patent to Joseph Reckendorfer for $100,000, who went to sue the pencil manufacturer Faber for infringement. In 1875 the Supreme Court of the United States ruled against Reckendorfer declaring the patent invalid.
The metal band used to mate the eraser with pencil is called a ferrule.
Manufacture
Modern pencils are made industrially by mixing finely ground graphite and clay powders, adding water, forming long spaghetti-like strings, and firing them in a kiln (thermally insulated chambers). The resulting strings are dipped in oil or molten wax, which seeps into the tiny holes of the material, resulting in smoother writing. 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.
Grading and classification
Two HB pencils. One is labelled #2 and the other #2 1/2.
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" (for fine point). The standard writing pencil is graded HB. According to Petroski this system might have been developed in the early 1900s 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.
Today 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; Derwent produces twenty grades from 9H to 9B for its Graphic pencils and Staedtler produces nineteen from 9H to 8B for its Mars Lumograph pencils. 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).
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.
Another common method uses numbers to designated the grade of a pencil. It was originally created by Conté and adopted in the United States by Thoreau in the 19th century.The following table shows approximate equivalences between the different systems:
Gummed Envelopes herringbone tape
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