The Providence news. (Providence [R.I.]) 1891-1906, 1892-02-05
MAKING LEAD PENCILS.
An industry That Has Been Carried
on Five Hundred Years.
AvARIETY OF DIFFERENT GRADES
The Use of Graphite I'm Early Ages-Pecu-
liarities of the substance-where 1t 10
Found = The Operations of Pencil
Making.

For quite 500 years graphite mas coen
used for the purposes OF writing ana
drawing. Pliny refers to Its use. and 80
does La Moin. and even Cortez mentions
It's use among the Aztecs. History also
shows that for ages graphite, under vari-
Gus names, has been distinguished from
metallic lead or Galena. The two sub
stances have no distinct property In COM
mon. Lead Is four times heavier than
graphite. Lead fuses at a low tempera-
ture. while graphite will scarcely fuse at
any temperature, but on the contrary
there is scarcely any known substance
that equals II In resisting heat.
II is one OF the softest substances In ma
ture, and chemists say 1t contains upward
OF ninety per cent. OF pure carbon. Science
makes some apparently contradictory
suggestions, for In asserting that the
diamond and graphite, substances so dis
similar In weight, hardness and appear
ance, are both almost pure carbon. yet IL
also informs us that carbon IL the element
that is consumed and Is susceptible to
heat in coal. But this seeming paradox
constitutes one Of the facts we stumble
over In our researches among the inscrut-
able works Of nature. Although charcoal
and lampblack approach In composition
both graphite and the diamond. still man
has been unable to produce by any art or
science the products as taken from the
earth.
lead is used in the manufacture OF lead
pencils, but on the other hand there is
abundance OF information showing the
use and reduction Of graphite In pencil
making. Native graphite is found In
many parts OF the world. and the famous
Barrowdale mine In Cumberland. Eng
land, has been worked since the middle OF
the sixteenth century. In the United
States there are mines that yield very
pure form OF graphite which our people
use In the various arts.
Frequently 1t exists In foliated or
crystalized formation running In veins
enclosed In hard rock, and then again II
appears In pockets or small veins, where
IL exists In a compact or granulated form
OF deposit. The foliated deposit Is largely
used In making crucibles and Is met with
under the name OF plumbago. while the
granulated formation is preferred for
pencil making. Pencil graphite is taken
from the mine, and by the use OF stamps
is reduced under water to an almost inn
paipable powder. After being submitted
to this pulver!zation the powder can
slip through the fingers with the evasive-
ness OF quicksilver.
When the dust Is taken from the stamp
mill IL Is mixed with water and permitted
to run through q series OF settling casks.
As IL passes from tub to tub the coarser
particles sink to the bottom, SO that the
last cask will necessarily contain the finer
grain The water is then carefully drawn
of, when the sediment is ready for q mix
ture with clay. For the finer grade OF
pencils only the sediment OF the last set
ting cask 10 used, the contents OF the
other casks being utilized In inferior
grades, which often give perplexing
scratchy mark. After the graphite is
taken from the cask 1t Is mixed with a
fine pipe clay and water into pasty
mass OF the consistency OF curd and then
thoroughly ground In mill.
The proportion OF clay mixed with the
graphite determines the hardness re-
quired, as the more clay used will produce
the corresponding harder pencil. After
grinding, the mixture is subjected to In
tense pressure, to expel the water, until ii
becomes OF the consistency OF glazler' 8
putty. The mass is then placed In bore,
something like the steam cylinder of an
engine. having piston at one end and a
plate at the other end perforated with a
hole Just the size OF the lead" desired.
The piston then forces the mass through
the aperture, which, as it issues In slender
strips, is cut off to the desired length and
finally baked in q crucible. After baking
the sticks are ready for the wooden pencil
cases. White pine is used for the cheap
grade OF pencils, red cedar for the ordi-
nary grades, and a selected quality OF the
lightest and closest grained cedar is util-
lied for the finest grade.
The wood Is usually cut In the saw mills
In blocks about seven inches long, which
are sawed into strips about a quarter oi
an Inch In thickness. The usual method
OF shaping the pencil Is by running the
strips through planer that burrows out
little groove for the reception Of the
stick OF graphite. II the strips have been
sawed three and one-half inches wide,
then six grooves will be cut in IT. The
"leads" or graphite sticks are then laid
| In the grooves, and another furrowed strip
coated with hot glue Ia placed upon IL,
both clamped together and set away to
dry. Six pencils In embryo now exist.
After the form has dried IL is run under
the cutter that saws out the six pencils
and at the same time the cutting knives
| give the pencil its desired form-either
round or hexagonal. The pencil then
passes through a colorlng vat, and then
through a curious little machine which
imparts D coat OF varnish and smooths
the ends. Stamping with the name OF
! the manufacturer and the grade OF the
pencil. and packing. closes the operation
next preceding shipment for market.
Until within the last twenty years Eng
land has monopolzed the pencil-makinR
industry. and even so late as ten years
ago American makers had to put for.
eign brand on their finest goods to meet
competition. But now the United States
leads probably both in the quantity and the
quality OF pencils manufactured. The in
vention OF machinery which superseded
the old method OF making a single pencil
at a time is due to American ingenuity
while the careful selection OF material has
further enabled home industries tc
achieve wonderful success.-St. Pau
4