delanceyplace.com 5/15/13 - an homage to the humble pencil
In today's selection—with the pencil increasingly marginalized by technology, we reflect on its relatively recent origin in the army of Napoleon Bonaparte. At least by the reckoning of one scientist, a single pencil can draw a line 731 miles (1178 kilometers) long:"The modern pencil was invented in 1795 by Nicholas-Jacques Conte, a scientist serving in the army of Napoleon Bonaparte. The magic material that was so appropriate for the purpose was the form of pure carbon that we call graphite. It was first discovered in Europe, in Bavaria at the start of the fifteenth century; although the Aztecs had used it as a marker several hundred years earlier. Initially it was believed to be a form of lead and was called 'plumbago' or black lead (hence the 'plumbers' who
mend our lead water-carrying pipes), a misnomer that still echoes in our talk of pencil 'leads'. It was called graphite only in 1789, using the Greek word 'graphein' meaning 'to write'. Pencil is an older word, derived from the Latin 'pencillus', meaning 'little tail', to describe the small ink brushes used for writing in the Middle Ages.
NICHOLAS-JACQUES CONTÉ
"The purest deposits of lump graphite were
found in Borrowdale near Keswick [England] in the Lake District in 1564
and spawned quite a smuggling industry and associated black economy in
the area. During the nineteenth century a major pencil manufacturing
industry developed around Keswick in order to exploit the high quality
of the graphite. The first factory opened in 1832, and the Cumberland
Pencil Company has just celebrated its 175th anniversary; although the
local mines have long been closed and supplies of the graphite used now
come from Sri Lanka and other far away places. Cumberland pencils were
those of the highest quality because the graphite used shed no dust and
marked the paper very well. Conte's original process for manufacturing
pencils involved roasting a mixture of water, clay and graphite in a
kiln at 1,900 degrees Fahrenheit before encasing the resulting soft
solid in a wooden surround. The shape of that surround can be square,
polygonal or round, depending on the pencil's intended use—carpenters
don't want round pencils that are going to roll off the workbench. The
hardness or softness of the final pencil 'lead' can be determined by
adjusting the relative fractions of clay and graphite in the roasting
mixture. Commercial pencil manufacturers typically market 20 grades of
pencil, from the softest, 9B, to the hardest 9H, with the most popular
intermediate value, HB, lying midway between H and B. 'H' means hard and
'B' means black. The higher the B number, the more graphite gets left
on the paper. There is also an 'F', or Fine point, which is a hard
pencil for writing rather than drawing.
"The strange thing about graphite is that
it is a form of pure carbon that is one of the softest solids known, and
one of the best lubricants because the six carbon atoms that link to
form a ring can slide easily over adjacent rings. Yet, if the atomic
structure is changed, there is another crystalline form of pure carbon,
diamond, that is one of the hardest solids known.
"An interesting question is to ask how long a straight line could be
drawn with a typical HB pencil before the lead was exhausted. The
thickness of graphite left on a sheet of paper by a soft 2B pencil is
about 20 nanometres and a carbon atom has a diameter of 0.14 nanometres,
so the pencil line is only about 143 atoms thick. The pencil lead is
about 1 mm in radius and therefore π square mm in area. If the length of
the pencil is 15 cm, then the volume of graphite to be spread out on a
straight line is 150π cubic mm. If we draw a line of thickness 20
nanometres and width 2 mm, then there will be enough lead to continue
for a distance L = 150π / 4 X 10-7 mm = 1,178 kilometres. But I haven't
tested this prediction!"| author: | John D. Barrow | |
| title: | 100 Essential Things You Didn't Know You Didn't Know | |
| publisher: | W.W. Norton & Company | |
| date: | Copyright 2008 by John D. Barrow |
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