A graphite pencil, also called a lead pencil, is a type of

pencil A pencil () is a writing or drawing implement with a solid pigment core in a protective casing that reduces the risk of core breakage, and keeps it from marking the user's hand. Pencils create marks by physical abrasion, leaving a tra ...

in which a thin

graphite Graphite () is a crystalline form of the element carbon. It consists of stacked layers of graphene. Graphite occurs naturally and is the most stable form of carbon under standard conditions. Synthetic and natural graphite are consumed on la ...

core is embedded in a shell of other material. The pencil shell is typically

wood Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin ...

en, but can be made of plastic or recycled paper.

History

A large deposit of

was discovered in 1565 on the approach to

Grey Knotts Grey Knotts is a fell in the English Lake District. It is situated one kilometre south of the B5289 road as it crosses the Honister Pass. It is well seen from mid-Borrowdale as it rises above Seatoller. Grey Knotts reaches a height of 697 met ...

from the hamlet of Seathwaite in Borrowdale parish,

Cumbria, England Cumbria ( ) is a ceremonial and non-metropolitan county in North West England, bordering Scotland. The county and Cumbria County Council, its local government, came into existence in 1974 after the passage of the Local Government Act 1972. Cumb ...

. Petroski, 1990, pp. 168, 358 This particular deposit of graphite was extremely pure and solid, and it could easily be sawn into sticks. It remains the only large-scale deposit of graphite ever found in this solid form.

Chemistry Chemistry is the scientific study of the properties and behavior of matter. It is a natural science that covers the elements that make up matter to the compounds made of atoms, molecules and ions: their composition, structure, proper ...

was in its infancy and the substance was thought to be a form of

lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cut, ...

. Consequently, it was called ''plumbago'' (Latin for "lead ore"). Because the pencil core is still referred to as "lead", or a "lead", many people have the misconception that the graphite in the pencil is lead, even though it never contained the element lead. The words for pencil in German (''Bleistift''), Irish (''peann luaidhe''), Arabic (قلم رصاص ''qalam raṣāṣ''), and some other languages literally mean ''lead pen''. The value of graphite would soon be realised to be enormous, mainly because it could be used to line the moulds for cannonballs; the mines were taken over by

the Crown The Crown is the state in all its aspects within the jurisprudence of the Commonwealth realms and their subdivisions (such as the Crown Dependencies, overseas territories, provinces, or states). Legally ill-defined, the term has differ ...

and were guarded. When sufficient stores of graphite had been accumulated, the mines were flooded to prevent theft until more was required. Graphite sticks were initially wrapped in string or

sheepskin Sheepskin is the hide of a sheep, sometimes also called lambskin. Unlike common leather, sheepskin is tanned with the fleece intact, as in a pelt.Delbridge, Arthur, "The Macquarie Dictionary", 2nd ed., Macquarie Library, North Ryde, 1991 Uses ...

for stability. England would enjoy a monopoly on the production of pencils until a method of reconstituting the graphite powder was found in 1662 in Italy. However, the distinctively square English pencils continued to be made with sticks cut from natural graphite into the 1860s. The town of Keswick, near the original findings of block graphite, still manufactures pencils, the factory also being the location of the Cumberland Pencil Museum.

Production

Production technology has changed little over the past 120 years; only standards and mechanisms for the manufacture of graphite rods and wooden halves have improved. The main components in the manufacture of rods – purified graphite powder and the clay binder

kaolin Kaolinite ( ) is a clay mineral, with the chemical composition Al2 Si2 O5( OH)4. It is an important industrial mineral. It is a layered silicate mineral, with one tetrahedral sheet of silica () linked through oxygen atoms to one octahedra ...

– remain the same; the hardness of the graphite core depends on the ratio of graphite to kaolin, with softer cores containing more graphite. The hardest pencil contains about 20% graphite, the softest one up to 90%. A 1:1 ratio roughly corresponds to the 3H hardness.

References

Bibliography

* {{Cite book , last=Petroski , first=Henry , year=1990 , title=The Pencil: A History of Design and Circumstance , location=New York , publisher=Alfred A. Knopf , isbn=978-0-394-57422-6 , ref=Petroski, 1990 , url=https://archive.org/details/pencilhistoryofd00petr_0 Pencils Visual arts materials

History

Production

See also

References

Bibliography