The Abbeville messenger. (Abbeville, S.C.) 1884-1887, 1886-09-14
LEAD PENCILS.
THE INTERESTING PROCESS OP
THEIR MANUFACTURE.
Graphite and its Peculiaritics-NiN
ing the Clay aud Forcing the Coil
d. Filling the Wooden Case
Separating and Shaping.

This is at the rate of one per day to
every 100 of population, or about 49,
600, 600 a year. Graphite, which is tho
softest substance dug from the earth, is
taken in the lump direct from the mouth
ofthe mine to the reducing mill. Hereitis
pulverizcd by stamps under water, tho
particles floating off with the water
through u series of tanks. It comes to
the factory in barrels, in the form of
dust. The powder is lustcrlcss and of
O dingy color. 1t is finer and softer than
any flour, and can be taken up in the
hand just as water can, but is hardly re-
tanned more easily than water is. If one
attempts to take a pinch of it between
the forefinger and thumb it is as evasive
as quicksilver, and the only sensation
left is that the flesh is smoother than
before.
The first process in manufacturing is to
separate the graphite dust further, &c
cording 10 tineness. It is mixed with
sufficient water to run very freely, and
is then turned into a hopper, from which
the water runs slowly through a series of;
tubs. The coarsest and heaviest partiI
Giles settle to tho bottom of the first tub,
the next coarsest and heaviest in the
next, and so on, the movement of the
water being made very gentle. On reach
ing the last tub, the powder, being twice
Us heavy Us water and sinking in it if
undisturbed, has so far settled that the
water discharged at the top is nearly
clear. After the flow is stopped and the
powder allowed to settle, the clear water
is withdrawn by removing SUCCESSFULLY,
beginning with the upper one, n number
of plugs inserted in holes in the side of
each tub, care being ed not to agitate
the contents so as to disturb the deposited
dust. This being done properly, the de-
post is removed through the gates at
the bottom of each tub The separation
is thus performed, by this ingenious pro-
cess of floating" more perfectly than
it could be by any direct handling, dry
treatment being wholly impracticable.
For the finest pencils the deposit from
the last tub only is used, but for ordi-
nary and cheap grades that from the two
before the last will answer.
The graphite is now ready for the clay.
This is q peculiar pipe clay from Ger.
many. After being subjected to the
floating process the finest is mixed with
the graphite, in proportions varying &C.
cording to the degree of hardness re.
quired. The more clay used the harder
the pencil. For medium grades the
proportion is about seven parts clay tc
ten graphite by weight. The graphite
and clay are mixed together with water,
to the consistency of thick cream, and
the mixture is fed to the grinding mills,
which consist of two fiat stones, about
two feet in diameter, placed horizontally,
only the upper n running. Between
these the mass is ground like paint, fol
the finest pencils as many as twenty-fou,
times, thus securing the most perfect
strength, uniformity and f~reeness from
grit in the leads. After grinding the
mass is inclosed in stout canvas bags, and
the clear water forced out by hydraulic
pressure until it becomes q thick dough.
1t then goes to the forming press. This
is simply q small vertical iron cylinder,
having a solid plunger, or piston driven
by a screw. A plate is inserted in the
bottom having an opening Of the shape
and size of the lead desired, and the
graphite is slowly forced through the
hole, exactly as water is forced from a
syringe, coiling itself round and round
like a coil of wire on o board set be-
meath the press. The coil is taken up ut
intervals, 'rove' off straight by the
hands into lengths sufficient for three
leads, which are Strengthened out, laid in
order on a board and pressed fiat by put
ting o cover over them. They are finally
hardened by placing them in a crucible
and baking in a kiln. The handling
must be done expeditiously, as the leads
begin drying Immediately and bec,mo
brittle as they dry; but on first issuing
from the press they are SO plastic that
knots may be tied loosely in them.
The leads are now ready for their
wooden case. For the cheapest pencil
pine is used. for the common grades an
ordinary quality of cedar. At the say
mills the cedar is cut into blocks, about
seven inches long, and these are sawed
into strips about three and a half inches
wide and three-sixteenths of an inch
thick. Thc pencil consists of two parts
glued together, with the lead between.