Pencil

A pencil is a handheld instrument used to write and draw, usually on paper. The writing is done with graphite (except for colored pencils), which is typically covered by a wooden sheath. Pencils may also have an eraser or "rubber" attached to one end. The pencil differs from most pens (other than erasable pens) in that erasing is possible.

A couple of very simple pencils.

Missing image Selection_of_colored_pencils.jpg Colored pencils are usually meant for drawing rather than writing.

Contents

1 History 2 Manufacture 3 Pencils in space 4 Miscellaneous 5 See also 6 References 7 External links

History

The prototypical pencil may have been the ancient Roman stylus, which was a thin metal stick used for scratching on papyrus, often made of lead. The word pencil comes from the Latin word penicillus which means "little tail".

In 1564, an enormous deposit of graphite was discovered at the site of Seathwaite Fell near Borrowdale, Cumbria, England. The locals found that it was very useful for marking sheep. This particular deposit of graphite was extremely pure and solid and it could easily be sawed into sticks. This was and remains the only deposit of graphite ever found in this solid form. Chemistry was in its infancy and the substance was thought to be a form of lead. Consequently it was called plumbago (Latin for "acts like lead"). The black core of pencils is still called "lead", even though it does not contain the element lead.

The value of plumbago was soon realised to be enormous, mainly because it could be used to line the moulds for cannon balls, and the mines were taken over by the Crown and guarded. Graphite had to be smuggled out for use in pencils. Because the plumbago was soft, it required some form of case. Plumbago sticks were at first wrapped in string or in sheepskin for stability. The news of the usefulness of these early pencils spread far and wide, attracting the attentions of artists all over the known world.

It was the Italians that first thought of wooden holders, at first by hollowing out a stick of juniper wood. Shortly thereafter, a superior technique was discovered: two wooden halves were carved, a plumbago stick inserted, and the two halves then glued together—essentially the same method that is in use to this day.

Although deposits of graphite had been found in other parts of the world, they were not of the same purity and quality as the Borrowdale find, and had to be crushed to remove the impurities, leaving only graphite powder. England continued to enjoy a monopoly on the production of pencils until a method of reconstituting the graphite powder was found. The distinctively square English pencils continued to be made with sticks cut from natural graphite into the 1860s. Today, the town of Keswick, near the original findings of block graphite, has a pencil museum.

The first attempt to manufacture graphite sticks from powdered graphite was in Nuremberg, Germany in 1662. They used a mixture of graphite, sulfur and antimony. Though usable they were inferior to the English pencils.

English and German pencils were not available to the French during the Napoleonic wars. It took efforts of an officer in Napoleon's army to change this. In 1795 Nicholas Jacques Conté discovered a method of mixing powdered graphite with clay and forming the mixture into rods which were then fired in a kiln. By varying the ratio of graphite to clay, the hardness of the graphite rod could also be varied (the more clay, the harder the pencil, and the lighter the color of the mark). This method of manufacture remains in use today.

Manufacture

Today, 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. 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 make something called a slat, and the graphite/clay strings are inserted into the grooves. Another grooved plank is glued on top, and the whole thing is then cut into individual pencils, which are then varnished or painted.

Many pencils, particularly those used by artists, are labelled on the European system using a scale from "H" (for hardness) to "B" (for blackness), as well as "F" (for fine point). The standard writing pencil is "HB". However, artist's pencils can vary widely in order to provide a range of marks for different visual effects on the page. A set of art 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 

The American system, using numbers only, developed simultaneously with the following approximate equivalents to the European system.

U.S.      Europe
#1     =     B
#2     =    HB   (most common)
#2 1/2 =     F   (also seen as 2 4/8, 2.5, 2 5/10, due to patent issues)
#3     =     H
#4     =    2H

Pencils in space

A story in circulation since the 1970s tells of NASA spending large sums of money, typically in the millions of dollars, to develop an instrument that would write in space (a space pen). This task is not as simple as it seems, for standard ballpoints and fountain pens require gravity in order to function. The typical punch line is that either someone sends NASA a pencil, or that the Soviets used pencils.

While humorous, it is not true (See Snopes (http://www.snopes.com/business/genius/spacepen.asp) for details). There are drawbacks to using pencils in space. The act of writing would cause graphite dust to come free from the lead and float about the cabin. From there it could become a health risk by being inhaled by the astronauts, clog filters in the ventilation system, or even cause short-circuits by getting into switches and other electrical equipment.

Miscellaneous

The pencil is a common cause of minor puncture injuries in young children. The tip of the lead may leave a grey mark inside the skin for years. This led to the old-wife's tale that the lead bits could be passed through the blood vessels into the brain, causing retardation in those with such a wound. Of course, pencil lead is graphite (carbon) and does not contain the element lead, so it is not poisonous.

Unrelated to imagined lead poisoning, however, pencils, like most other sharply pointed objects, may be used to cause injuries by stabbing or piercing, as depicted in the 1999 horror movie House on Haunted Hill, where a man is stabbed through the neck by a dozen pencils.

See also

• mechanical pencil
• ballpoint pen
• fountain pen
• Dixon Ticonderoga
• pencil lead
• pencil case
• pencil sharpener

References

• Petroski, Henry (1990). The Pencil: A History of Design and Circumstance. New York: Alfred A. Knopf. ISBN 0394574222; ISBN 0679734155.

External links

• The Pencil Pages (http://www.pencilpages.com/) – A website containing history, numbering systems, and other pencil information
• The Cumberland Pencil Museum in Keswick (http://www.pencils.co.uk/)
• History of pencils, pencil lead; details of modern pencil manufacture (http://pubs.acs.org/cen/whatstuff/stuff/7942sci4.html) – An article from the American Chemical Societybg:Молив

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