Daily press. [volume] (Newport News, Va.) 1896-current, 1905-10-05
BLACK LEAD PENCILS
THEIR MANUFACTURE AND THE MA
TERlALS THEY CONTAIN.

The TIumbnGO Comes Mainly From
bavaria and the Rcd Cedar Wood
From FlorIdn-tIow the Graphite Is
Manipulated TO Form the Leads.
The first pencils in the modern sense
were simply pieces of pure plumbago.
the more common name of which Is
black lead or graphite. This mineral
has always been rare, and as the very
qualities OF softness and blackness
which made 1t good to mark with made
1t also disagrecable to handle 1t was
not long before Il covering Of wood was
provided, partly to protect the hand
and partly TO cconomzc the plumbago
The best graphite in the world has
been taken from mines in Borrowtlalc
England, and in eastern Siberia. The
quality in both places was such that
solid slabs of It could he sawed out
and these in turn cut into the slender
strips which form the leads of mod
ern pencils. The quality, however
was not sufficient to permit this meth
ID to be adopted exclusively. The
Borrowdale mines indeed have long
since been exhausted. Most of the
Plumbago for the bcst pencils now
nndcrgocs number of processes. 1t is
mined i'll irregular Jumps or in any
form in which it may be got out most
chcaply. Shipped to the pencil fac
tory, il Is there ground and mixed with
finely pulvcrized clay in quantities
which depend upon the hardness or
softness Which the pencils are to pos
scss. For hard pencils, such as are
craftsmen. the mixture is one part of
plumbago 20 two parts OF clay. The
softer tho pencil the greater the pro-
portion Of plumbago.
The mixture is "thnncd" with wa-
ter and repeatedly, ground until 1t Is
perfectly smooth and free from grit
1t is then placed IN canvas bags and
squeezed by machinery until enough
water has been removed to leave II
tenacious. doughlilie mass, from which
the leads are to be formed.
The dough" as it is called, is
placed in strong steel cylinder, one
end Of which Is perforated with holes
of the same size us the leads which IL
is desired to make. The pressure of Il
slowly descending piston forces the
dough" out through the holes In long
strings, which are quickly removed
and laid In groovcd or on ce.ltcd
boards TO straighten and dry.
Tho next step Is the temperlng of the
leads by hcnting to red heat in cru.
cibles. by this process the hardness
or softness OF the pencils is still fur
Their modified, impurities are burned
out and the little strips of plumbngo
are considerably strengthened. They
are now ready for their wooden cases.
These in all the better grades of pen.
ellis are made Of red cedar, most OF
which comes from Florida. This wood,
better than anything else, answers the
requirements of softness and straight.
ness of grain and permanency.
The wood Is sawed by machinery
into strips. two of which when placed
together are equal to the diameter of
the pencil. But if the lead Is TO be
square the two strips are not of crlual
thickness. That which contains the
groove for the lead is thethIcler.. Most
pencils. however, have round leads.
ullu Ill uliS case Tie TWO StrlpS are of
equal thickness, and each contains n
semicircular groove.
The lead Is now inserted in the
groove and the two strips are glued
together When dry, they aro' passed
through circular cutter similar to,the
so called hollow bits by which thclends
Of ladder rungs are rounded anil dow
els nre made. They emerge at the
other end perfectly rounded. Nothing
remains but cutting the sticks into
suitable lengths, painting or polishing.
and stamping with the makers name
and the degree of hardness.
Pencils made of the pure graphite
would not be superior to thosein which
the graphite is mixed with clay. The
modern pencils possess not only great
or strength, but there are fewer gritty
spots. and they correspond more regu-
larly to the marks which are stamped
upon them.-Edward .Willistoni Frcntz
In Youths Companion.